encouraging and fruitful scientific conversations, for his openness and readiness to help both in scientific and life questions. I also appreciate he made possible my research visits to Mexico thus opening so many opportunities to know new people, culture and establish new scientific contacts. I would like also to say thank you to Dr. Lacroix for the time he spent to teach me a

José Norberto Farfán García at UNAM and I am very thankful to him for making possible my comfort and fruitful stay in Mexico, for providing nice conditions for work and collaboration with researchers of his group and for interesting scientific discussions. I would like also to say thank you to Dr. Rosa Luisa Santillan Baca, and Professor Farfan's big family for opening the possibilities to discover the culture of Mexico and for always being responsive and helpful. I would like also to express many thanks to Professor Blas Flores Pérez, who has kindly provided the facilities for the research work in UNAM. I am very much thankful to PhD Alejandro Enriquez-Cabrera for his readiness to help in any question regarding research work or everyday life and for providing a valuable help in the questions of synthetic chemistry. I am also very much obliged to him and his big family for nice treatment and hosting me during my stay in Mexico.

Many thanks to Margarita Romero-Ávila for her invaluable help and guidance in many complex problems in synthetic organic chemistry, for her support and sensitiveness. I would like to express my gratitude to Andrés Felipe Leon-Rojas, a student of Professor Farfan's research group, for nice collaboration and help in synthetic part of the work. I gratefully acknowledge Dr. Gabriel Ramos-Ortiz (CIO, Leon, Mexico) for his kind attention and solicitude and for providing conditions and facilities to conduct the optical measurements. I am thankful to Rodrigo Misael Barba-Barba and PhD Jayaramakrishnan Velusamy for substantial help in measuring the twophoton absorption parameters of the complexes.

INTRODUCTION

Last decades, since nitric oxide was proclaimed "Molecule of the Year" by the journal "Science", many research teams has been aiming at in-depth study of physiological role of NO. Nowadays this compound is considered one of the main constituents in biological processes. The idea of a controlled nitric oxide release has become very attractive, for instance in order to be able to cause a selective influence on malignant cells. Indeed, depending on concentration, NO can inhibit the tumour growth or lead to the cell apoptosis. Exogenous NO-donors as modifiers of NO-levels in biological tissues are one of the most promising ones. Snitrosothiols, organic nitrates, sydnonimines are practically important nowadays.

Especially interesting group of promising potent NO-donors is metal-nitrosyl complexes, in particular ruthenium-nitrosyls. The last ones are stable in aqueous media as opposed to the majority of alternative metal-nitrosyls. But the most important advantage of ruthenium-nitrosyl complexes is their ability to release NO under irradiation exclusively, that makes them perfect candidates as prodrugs for photodynamic therapy.

One of the targets for modern photodynamic therapy is the development of photosensitization methods of prodrugs in optical therapeutic window (700-1300 nm). Beyond this range of wavelengths the activation is ineffective due to a high extinction of electromagnetic waves intensity because of their absorption by biological tissues. Most of known photoactive NO-donors nowadays are able to release NO while being activated with waves of 350-600 nm waveband. Therefore the question of photosensitization of such compounds in vivo is a keystone for their future implementation in medical practice.

One of approaches, opening up the possibilities for photoinitiation of Ru-N bond dissociation in ruthenium-nitrosyl complexes in optical therapeutic window is two-photon absorption (TPA). This modern method has not been widely implemented in medical practice, however it is being thoroughly studied by scientists of different fields of science and technology -from medicine and microconstruction to 3D-data storage. High spatial selectivity of electromagnetic waves influence on organism and reduced destructive effect (when employing IRrange waves) makes the local NO-release without damage dealt to adjacent tissues possible.

Revealing of main structural elements of ruthenium-nitrosyl coordination compounds capable of participating in two-photon absorption process and understanding the mechanism of NO-release process, is thereby an actual task in designing of promising NO-donors prodrugs.

CHAPTER 1. LITRERATURE OVERVIEW 1.1 Nitric oxide: molecular structure and general chemical characteristic.

Nitric oxide (or nitrogen monoxide) is a colorless gas, which is monomeric at standard conditions; its molecules consist of an oxygen atom and a nitrogen atom connected by a multiple bond. Odd number of electrons in NO molecule makes the substance paramagnetic; in addition, it is the smallest thermally stable moleculeradical known. In terms of the molecular orbital method, it is logical to compare the structure of the compound with the structure of N 2 molecule or with one isoelectronic to it -CO (figure 1.1). Appearance of an additional electron (in transition from nitrogen to nitric oxide), which is located on the antibonding g NO orbital causes decreasing of the bond order from 3 (for N 2 molecule) to 2.5 (for NO molecule). This has a corresponding effect on the nitrogen monoxide physical and chemical properties.

In particular, bond length in NO molecule is 0.115 nm. It is an intermediate value between the length of the typical double bond N-O (0.120 nm) and the interatomic distance in ionized NO + particle (0.106 nm), which bond order is 3. 1 And vice versa reducing the compound to NO -increases the bond length to 0.126, which is caused by appearance of one more electron on the molecular antibonding orbital and decrease of the potential is 9.25 eV; t compounds which is ca an electron from the an the following compou respectively. In practice be distinguished by an particle. Thus, for nitro is well over the one for -1470 cm -1 . 2 Realization of ele explanation of its coord Being the simplest molecule with an odd number of electrons, nitrogen monoxide is a rather well studied compound from the point of view of its chemical properties. A great number of reactions between NO and radicals, atoms and other paramagnetic species became classical unique examples of reactions for kinetics study.

There are several number of commonly used laboratory methods of NO generation. Though the obtained nitric oxide as a rule contains impurities of other nitrogen oxides or volatile compounds. The most used method is reduction of dilute (~30%) nitric acid by copper:

8HNO 3 + 3Cu = 3Cu(NO 3 ) 2 + 4H 2 O + 2NO
NO synthesized in this way is to be later purified in order to remove the impurity of nitrogen(IV) oxide by running the mixture of generated gases through aqueous solution of alkali. Another method of NO obtaining is reduction of alkaline metal nitrites: An up-to-date but considerably more expensive method of obtaining NO in laboratory conditions is use of so-called NONOate-compounds. The method is used when controllable NO synthesis is essential, for example, in biological studies (see section 1.3.2)

In contrast to nitrogen, nitric oxide is an endothermic compound, therefore it is less stable. Even at a temperature slightly higher than the room temperature (30-50°C), but only under high pressure, nitrogen monoxide disproportionates with generating nitrogen(I) oxide and nitrogen(IV) oxide. Decomposition to the elementary substances is happening at significantly higher temperature -close to 700 0 C in the presence of a catalyst.

Strong oxidizers can convert nitric oxide into compounds where nitrogen has higher oxidation states. 5 The most typical nitric oxide reaction is interaction with oxygen, at which the compound is oxidized to nitrogen(IV) oxide:

2NO + O 2 = 2NO 2
Whereas interaction of NO with atomic oxygen, at which chemiluminescence is observed, was used for qualitative and quantitative determination of atomic oxygen: 6 NO + O = NO 2 + h Naturally, the presence of water in nitrogen monoxide and oxygen interaction changes the reaction path since NO 2 itself can react with water. That's why as a result of NO-oxidation by oxygen in humid condition nitrite-ions are generated.

The reaction is commonly described by the following equation: It was the discover of the role of this small molecule as a signaling molecule in cardiovascular and nervous systems that aroused so rapidly an increasing interest to it. In 1992 the journal Science called nitric oxide "Molecule of the year" and in 6 years, December 10, 1998 the Nobel prize for physiology and medicine was given to three researchers from the USA -Robert F. Furchgott, Louis G.

Ignarro and Ferid Murad -for investigation of nitric oxide biological functions.

Physiological effects caused by nitrogen monoxide influence onto biological environment are often contradictory. [START_REF] Wink | The Cytotoxicity of Nitroxyl: Possible Implications for the Pathophysiological Role of NO[END_REF] For instance, nitrogen monoxide is the best example of a substance that demonstrates at the same time both cytotoxic and cytoprotective action.

A large number of chemical reactions characteristic for NO, in industrial or laboratory routine proceed quite slowly and thus requires using high temperature and pressure being at the same time thermodynamically disadvantageous [START_REF] Thomas | Free Radical Biology & Medicine The Chemical Biology of Nitric Oxide : Implications in Cellular Signaling[END_REF] . From the other side, nitric oxide chemical transformations in biological environments take time from 0.002 to 2 s. [START_REF] Hill | What Part of NO Don't You Understand? Some Answers to the Cardinal Questions in Nitric Oxide Biology[END_REF] These processes in NO biochemistry are usually divided into two types: direct and indirect. Direct effects caused by NO proceed quite fast and during them nitric oxide interacts directly with a biological target, whereas indirect ones are the results of NO interaction with oxygen or superoxide, that generates reactive nitrogen species (RNS), further interacting with biological objects. One of the advantages of such a differentiation is that the direct effects are caused generally by low NO concentrations ( 200 nM), while the indirect ones are the results of influence of significantly higher concentrations ( 400 nM). [START_REF] Thomas | Free Radical Biology & Medicine The Chemical Biology of Nitric Oxide : Implications in Cellular Signaling[END_REF] Nitric oxide principal biological functions are generalized on diagram 1.1. [START_REF] Thomas | Free Radical Biology & Medicine The Chemical Biology of Nitric Oxide : Implications in Cellular Signaling[END_REF][START_REF] Hill | What Part of NO Don't You Understand? Some Answers to the Cardinal Questions in Nitric Oxide Biology[END_REF][START_REF] Feelisch | The Chemical Biology of Nitric Oxide -an Outsider ' S Reflections about Its Role in Osteoarthritis[END_REF] Scheme 1.1. Nitric oxide biological functions.

The main difference between direct and indirect processes is rate of its proceeding. High-speed reactions of immediate interaction between NO and biomolecules -mainly reactions with radicals or metalloproteins -are the direct processes.

A large number of NO main regulatory functions realize through its easy and rapid interaction with metalloprotein heme-prosthetic groups, such as guanylate cyclase (sGC), cytochrome P450, NO-synthase, hemoglobin etc. In such kind of processes the rate-determining step is diffusion of reacting molecules. Process of interaction between nitric oxide and Fe-S cluster protein aconitase proceeds considerably slower. [START_REF] Miranda | The Chemical Biology of Nitric Oxide[END_REF] Biomolecules having in their structure other metal ions, apart from Fe, are also susceptible to the influence of NO. This type of interaction could be represented by the vitamin B 12 derivative, cobalamin, the nitrosylation of which leads to its reduced activity in the role of a cofactor of methionine synthase.

Reactions between nitric oxide and radical particles can have both positive and negative effects on cells. Lipidic and carboradicals are generated as a result of both oxidative stress and normal metabolism in a living organism. Nitrogen monoxide is able to attenuate effects caused by such reactive particles. For example, inactivation of tyrosyl radical generated in the process of ribonucleotidereductase regular catalytic cycle by nitric oxide leads to inhibition of the mentioned enzyme. [START_REF] Lepoivres | Quenching of the Tyrosyl Free Radical of Ribonucleotide Reductase by[END_REF] DNA synthesis suppression is an example of harmful effects of NO interaction with radicals in biological environment. [START_REF] Miranda | The Chemical Biology of Nitric Oxide[END_REF] But it is often that the reactions of NO are of the nature of "protective" functions for cells. NO is able to interact with radicals generated in the process of lipidic peroxidation -an important component of inflammatory processes and cell death -and so terminate the chains of reactive oxygen species (ROS) radical reactions, thus protecting the lipidic membranes: [START_REF] Padmaja | The Reaction of Nitric Oxide with Organic Peroxyl Radicals[END_REF]

LOO• + NO• = LOONO L• + NO• = LNO

Macrophages protective functions in a living organism are also related to their ability to generate nitric oxide. Concentration of the latter in this case can considerably change depending on the "needs". Due to the ability to vary NO concentration macrophages are able to participate in a wide range of processes aimed at organism protection -phagocytosis, cancer development suppression, tissues restoration, wounds healing etc.

As for NO indirect effects, they also can be divided into two categoriesnitrosation and oxidation. The subjects of nitrosation are, first of all, thiol and aminogroups while oxidation is a process that refers to quite a number of substrates -from relatively easily oxidizable catecholamines and metal centers to compounds with a high oxidation-reduction potential, such as lipids, proteins DNA. As in the case of the direct effects, oxidation and nitrosation are regular cell metabolism processes but at the same time they can influence negatively generating substances toxic for cells.

Main RNS responsible for nitrogen(II) oxide indirect effects are nitrogen(III) oxide, N 2 O 3 , peroxynitrite, ONOO -, nitroxyl, HNO, and nitrogen(IV) oxide, NO 2.

Each of the particles depending on the redox potential, electrophilicity etc.

interacts with certain biological substrates. Thus, the main nitrosating agent for amines and thiols is N 2 O 3 , which transforms them into nitrosamines and Snitrosothiols, respectively. [START_REF] Miranda | The Chemical Biology of Nitric Oxide[END_REF] In turn, NO 2 participates in oxidation processes. The molecule does not possess potential high enough for DNA oxidation [START_REF] Routledge | Nitrite-Induced Mutations in a Forward Mutation Assay: Influence of Nitrite Concentration and pH[END_REF] but it can trigger lipidic peroxidation processes. [START_REF] Koppenol | a Cloaked Oxidant Formed by Nitric Oxide and Superoxide[END_REF] Among the mentioned particles, peroxynitrite anion shows the strongest oxidizing ability. Under its influence, thiols, lipids, DNA can be oxidized, this particle also participates in the processes of tyrosine, guanosine and methionine nitration. [START_REF] Koppenol | a Cloaked Oxidant Formed by Nitric Oxide and Superoxide[END_REF] Nitric oxide has a broad spectrum of effects on cancer growth -from triggering cell mutation to destructing malignant tumours. There are several reviews devoted to nitric oxide effects on the course of cancer. [START_REF] Bonavida | Therapeutic Potential of Nitric Oxide in Cancer[END_REF][START_REF] Choudhari | Nitric Oxide and Cancer : A Review[END_REF] Numerous studies on the issue show that commonly nitrogen monoxide low concentrations in cancerous tumour, which is a result of permanent hypoxia, create so-called "safe zone" and are a positive factor for cancer extension, promoting faster angiogenesis and metastasis (Figure 1.3). [START_REF] Fukumura | The Role of Nitric Oxide in Tumour Progression[END_REF][START_REF] Oronsky | The Implications of Hyponitroxia in Cancer[END_REF] If, however, NO concentration changes in the direction of decreasing or increasing this leads to transferring to the "inhibition zone" or to the "kill zone", respectively. Both concentration ranges are unfavorable

for cancerous tumors and are potential targets in their treatment. Transferring to the very low concentrations range can be achieved by using NO-synthases (NOS) enzymes inhibitor compounds in therapy. The opposite approach is using nitric oxide donor compounds for NO concentration essential increasing, transferring to the "kill zone" and triggering cell death.

Generalizing the effects that NO can cause in the concentration range from 1nM to 1 M, we can say that NO low concentrations promote cells protection, their proliferation while high concentrations are responsible for blocking cellcycle, apoptosis, aging. [START_REF] Thomas | Free Radical Biology & Medicine The Chemical Biology of Nitric Oxide : Implications in Cellular Signaling[END_REF] Besides, NO plays a central role in the cardiovascular system as an endothelium-dependent relaxing factor, [START_REF] Furchgott | The Obligatory Role of Endothelial Cells in the Relaxation of Arterial Smooth Muscle by Acetylcholine[END_REF] in the central nervous system it is involved in the nerve impulses transmission and memory processes, and also performs a regulatory function in the cerebral circulation.

Having chosen nitric oxide as such a multifunctional biological regulator, nature provided living organisms with mechanisms of its biosynthesis. Initially, the 2-electron oxidation of L-arginine and its hydroxylation in the presence of oxygen and NADPH [START_REF] Knowles | Nitric Oxide Synthases in Mammals[END_REF] leads to the formation of N -hydroxy-Larginine (NOHLA). Tetrahydrobiopterin accelerates the course of this step acting as a cofactor. [START_REF] Kwon | L-Citrulline Production from L-Arginine by Macrophage Nitric Oxide Synthase[END_REF] Further NOHLA oxidation (the next transformation step) leads to the formation of L-citrulline and one molecule of nitric oxide. The general scheme of the conversion of L-arginine to L-citrulline can be described by the following equation:

2L-arginine + 3NADPH + 3H + + 4O 2 = 2L-citrulline + 2NO + 4H 2 O + 3NADP + Moreover there are four other cofactors, the absence of which either slows the reaction or makes it impossible to pass. [START_REF] Sonveaux | Nitric Oxide Delivery to Cancer : Why and How ?[END_REF] The NOS enzyme group includes three main enzymes -endothelial NO synthase (eNOS), neuronal NO synthase (nNOS), and inducible NO synthase (iNOS); the fourth type -mitochondrial synthase (mtNOS) is identical with the -form of nNOS. [START_REF] Sonveaux | Nitric Oxide Delivery to Cancer : Why and How ?[END_REF] The first two enzymes are calcium-dependent and are activated in the presence of high concentration of calcium ions by calcium-calmodulin complex; typically, their activity period does not exceed few minutes after stimulation. Activated eNOS and nNOS are involved in the conduction of nerve impulses, peristalsis regulation and instantaneous regulation of blood pressure. [START_REF] Nathan | Nitric Oxide Synthases : Roles , Tolls , and Controls[END_REF] Although all three forms of NOS require a calciumcalmodulin complex, iNOS exhibits a much higher affinity for it, which leds to longer activity period (up to days) and lower calcium-calmodulin complex concentration required. [START_REF] Sonveaux | Nitric Oxide Delivery to Cancer : Why and How ?[END_REF] iNOS activation is the response to the internal stimulation with a variety of microorganisms metabolic products, some cancer cells, cytokines etc. Activated enzymes produce millimolar amounts of NO (interacting with ROS peroxynitrite), showing an immune-protective function by oxidizing proteins and DNA. [START_REF] Nathan | Nitric Oxide Synthases : Roles , Tolls , and Controls[END_REF] However, in the lack of oxygen (i.e. chronic inflammatory processes), the level of RNS can be significantly lower, and the nitric oxide provokes mutagenesis and angiogenesis instead, thus connecting directly inflammation and the initiation of cancer. [START_REF] Sonveaux | Nitric Oxide Delivery to Cancer : Why and How ?[END_REF] Considering such a large number of biological processes in which nitric oxide is involved and which in its absence or its low concentration slow down, stop or activate undesirable chemical reactions causing a number of diseases, it seems attractive to obtain a mechanism for regulating the concentration of NO in living organism.

Classical donors of nitric oxide based on organic compounds.

Nitric oxide donors or NO-donors is a group of compounds or functional fragments of supramolecular systems that can release nitrogen monoxide when exogenously applied. [START_REF] Kim | A Platform for Nitric Oxide Delivery[END_REF] Lack of NO in a particular place of a living organism can trigger a number of pathological processes that will manifest themselves as symptoms of various diseases. Although free nitric oxide is used successfully for medical purposes (locally, for the treatment of dermatitis, [START_REF] Carpenter | Nitric Oxide Release : Part II . Therapeutic Applications[END_REF] or in the form of inhalations in pulmonary hypertension in newborns [START_REF] Ivy | Pediatric Pulmonary Hypertension[END_REF] ), the use of NO-donors can significantly increase the range of possible exogenous effects on the body. [START_REF] Carpenter | Nitric Oxide Release : Part II . Therapeutic Applications[END_REF] Chemical stability and the capability of local NO elimination of NO-donors allow the controlled delivery of nitrogen monoxide to various parts of the living organism.

NO-donors can be divided into several groups depending on the method of NO-release activation. According to the classification proposed by Philish and Stamler, [START_REF] Feelisch | Donors of Nitrogen Oxides[END_REF] three major groups can be distinguished: 1) NO-donors that liberate NO spontaneously; 2) NO-donor that release NO after chemical interaction with acids, alkalis, metals, thiols; 3) NO-donors that release nitric oxide after their enzymatic oxidation (Scheme 1.3). Organic nitrates are the most widespread example of NO-donors. Since they were the first approved drugs used for NO-level control they are worthy of special attention. Organic nitrates are esters of alcohols (polyols in general) and nitric acid.

Glyceryl trinitrate (GTN) is the most thoroughly studied compound of this class (Figure 1.4). Its use is not limited to vasodilating effects on the vessels.

Among the pathologies for the treatment of which the use of GTN is approved, one can mention cardiac dysfunctions [START_REF] Agvald | Mechanisms of Nitric Oxide Generation from Nitroglycerin and Endogenous Sources during Hypoxia in Vivo[END_REF] , hypotension and headaches, [START_REF] Huerta | Nitric Oxide Donors : Novel Cancer Therapeutics ( Review )[END_REF] angina and cancer. [START_REF] Yasuda | Nitric Oxide Solid Tumor Physiology and Hypoxia-Induced Chemo / Radio-Resistance : Novel Strategy for Cancer Therapy : Nitric Oxide Donor as a Therapeutic Enhancer[END_REF] Other drugs used are isosorbide dinitrate (ISDN), pentaerythril tetranitrate (PETN), isosorbide-5-mononitrate (ISMN) (Figure 1.4). [START_REF] Daiber | Organic Nitrate Therapy, Nitrate Tolerance, and Nitrate-Induced Endothelial Dysfunction: Emphasis on Redox Biology and Oxidative Stress[END_REF] The mechanisms by which the nitric oxide is liberated from organic nitrates are still contradictory. However, the proposed schemes include the stage of interaction with one of the enzymes: glutathione-S-transferase, cytochrome P450, xanthine oxidoreductase, aldehyde dehydrogenase. [START_REF] Parker | Nitrate Therapy for Stable Angina Pectoris[END_REF] The use of organic nitrates can lead to a number of side effects, [START_REF] Daiber | Organic Nitrate Therapy, Nitrate Tolerance, and Nitrate-Induced Endothelial Dysfunction: Emphasis on Redox Biology and Oxidative Stress[END_REF] since these drugs show their effects in the body in whole, without specific localization.

Glycerinetrinitrate

However, the most significant disadvantage of using organic nitrates is the tendency of the body to rapidly developed tolerance to these compounds. [START_REF] Bogaert | Tolerance towards Glyceryl Trinitrate (Trinitrin) in Dogs[END_REF] This feature of organic nitrates can be very useful in the treatment of cancer.

The growth of cardiovascular tolerance to GTN allows its use in complex cancer therapy, along with cytostatic drugs (i.e. doxorubicin) without systematic side effects from continuous high NO levels. Research on the use of such a combination in the treatment of mice prostate cancer shows a more effective inhibition of tumor growth than in the treatment of exclusively doxorubicin. [START_REF] Frederiksen | Chemosensitization of Cancer in Vitro and in Vivo by Nitric Oxide Signaling[END_REF] Other commonly used compounds in cancer treatment studies are Snitrozotioles, diazeniumdiolates (NONOate) and sydnonimines (Figure 1.5). Snitrosothiols are compounds with a nitroso group which is directly linked to the sulfur atom. Most compounds of this class are unstable, but several of them are sufficiently stable and have already proven themselves as active drugs (i.e. Snitroso-N-acetylpenicillamine (SNAP)) (Figure 1.5). [START_REF] Huerta | Nitric Oxide Donors : Novel Cancer Therapeutics ( Review )[END_REF] S-nitroso-Nacetylpenycillamine (SNAP)

3-morpholine- sydnonimine hydrochloride (SIN-1) Sodium (Z)-1-(N,N- diethylamino)diazen- 1-ium-1,2-diolate Figure 1.5.

Representatives of other classes of NO-donors used in oncology practice

The main advantage of S-nitrosothiols is better biocompatibility compared to other NO-donors, in particular NONOate. This conclusion comes from the fact that S-nitrosothiols are naturally present in biological systems, as for instance Snitroso-L-cysteine (CysNO) or S-nitroso-L-glutathione (GSNO). [START_REF] Michele | Polymer-Based Nitric Oxide Therapies: Recent Insights for Biomedical Applications[END_REF] The mechanism of NO-release from S-nitrosothiols is strongly dependent on the external conditions (Scheme 1.4).

Scheme 1.4. Mechanisms for the release of nitric oxide from Snitrosothiols

O N N N O H 2 N + Cl - O N S O OH HN O N N N O - O Na +
Despite the large number of publications devoted to the study of these compounds in vivo, they have not yet found direct application in medicine. Their ability to release NO in different environments, the ability to release it in the form of a radical or nitrosonium-cation, predictable pathway of metabolic degradation, and an almost complete absence of tolerance development with prolonged use -all these benefits make S-nitrosothioles compounds of interest as nitric oxide donors in medical practice. [START_REF] Miller | Recent Developments in Nitric Oxide Donor Drugs[END_REF] Another class of NO-donors is diazeniumdiolates (or NONOates). These compounds are known since the 1960s, when its first DEA/NO agent was synthesized for the first time. [START_REF] Drago | The Reaction of Nitrogen(II) Oxide with Diethylamine[END_REF] However, they became the object of numerous studies only in the 90s of the last century, [START_REF] Miller | Recent Developments in Nitric Oxide Donor Drugs[END_REF] NONOates play significant role in biology. [START_REF] Michele | Polymer-Based Nitric Oxide Therapies: Recent Insights for Biomedical Applications[END_REF][START_REF] Reynolds | Nitric Oxide-Releasing Hydrophobic Polymers: Preparation, Characterization, and Potential Biomedical Applications[END_REF] Under physiological conditions (pH 7.4 and temperatures of 37 °C), compounds of this class undergo acid hydrolysis producing 2 equivalents of nitric oxide per diazeniumdiolate group: [START_REF] Huerta | Nitric Oxide Donors : Novel Cancer Therapeutics ( Review )[END_REF][START_REF] Reynolds | Nitric Oxide-Releasing Hydrophobic Polymers: Preparation, Characterization, and Potential Biomedical Applications[END_REF] Spontaneous NO release, no need for additional activators of this process (i.e. thiols, metal complexes or enzymes), first order reaction rate moves diazeniumdiolates in one row with S-nitrosothiols and sydnonimines of promising NO-donors.

Easy predictable NO-liberation rate and its final concentration are important qualities of NONOate, due to which compounds of this class are widely used in studies aimed at desing of anticancer drugs. [START_REF] Kim | A Platform for Nitric Oxide Delivery[END_REF] On the other hand, the main advantage easily transforms into the serious drawback when using this compound as drug -NO-donors based on NONOate can release NO before reaching the main target. The use of targeted drug delivery can help to overcome this disadvantage, although it significantly complicates the drug preparation process.

One of approaches of targeted delivery of this class of compounds is demonstrated in the paper of Wang and coworkers. [START_REF] Tang | Synthesis of Peptide-Diazeniumdiolate Conjugates: Towards Enzyme Activated Antitumor Agents[END_REF] Using one of NONOates -PYRRO/NO compound as NO-donor, the researchers inactivated the compound by binding it with a certain amino acid sequence through the oxygen atom of the diolate group. The use of amino acid sequence of one segment of the substrates of prostate-specific antigen (PSA) allowed making modified PYRRO/NO compound sensitive to the presence of this enzyme. PSA is an enzyme produced by both healthy and cancerous cells of the prostate epithelium in significant amounts. [START_REF] Tang | Synthesis of Peptide-Diazeniumdiolate Conjugates: Towards Enzyme Activated Antitumor Agents[END_REF] Increased concentration of this enzyme is observed in metastases of prostate cancer.

The resulting PYRRO / NO based drug must be inactive before hydrolysis that occurs in the presence of PSA or -chymotrypsin. As a result, spontaneous release of NO in vitro from the resulting compound was observed only in the presence of one of these enzymes in solution (Scheme 1.5). 42 Ohta. [START_REF] Wang | Nitric Oxide Donors: Chemical Activities and Biological Applications[END_REF] Under normal conditions and in the absence of light sydnonimines are stable solids.

Sydnonimines release nitric oxide in an alkaline medium and the passage of this process is greatly facilitated by the presence of oxygen or under excitation with UV irradiation. The most studied example of this class is

O O Peptide O N N N O - + -O O N N N O - + -O N N N O - + NO PSA -RCO 2 -H 2 CO
3-morpholinosydnonimine (SIN-1, linsidomine) (Figure 1.5). The medicinal product under the brand name "Molsidomine" is based on this compound. The release of NO from this product is shown in Scheme 1.6. [START_REF] Bohn | Oxygen and Oxidation Promote the Release of Nitric Oxide from Sydnonimines[END_REF] The first step of decomposition is the enzymatic deacetylation of molsidomine in the liver with the formation of linsidomine. At physiological or alkaline pH linsidomine undergoes a non-enzymatic cycle opening. The formed product is completely stable at pH 7.4 in absence of oxidants, but even small amounts of oxygen lead to the formation of radical cation which decays producing nitric oxide and N-morpholinoaminoacetonitrile.

Scheme 1.6. NO-release from medicinal product "Molsidomine"

Typically sydnonimines donate NO in peroxynitrite anion form. [START_REF] Wang | Nitric Oxide Donors: Chemical Activities and Biological Applications[END_REF] As shown on the Scheme 1.6 during the molsidomine transformation the stoichiometric amount of the superoxide radical is formed, and since the interaction of nitrogen monoxide with the superoxide radical is extremely rapid and the diffusion is the only limiting process, the formation of toxic peroxynitrite is inevitable. This feature of sydnonimines, of course, reduces the spectrum of their possible use in medicinal purposes. The advantage of these compounds is that addiction to them does not appear, and a tolerance to sydnonimines does not arise even with prolonged use.

Nitrobenzenes as examples of photoactive NO-donors

The ultimate goal of most studies of nitric oxide donors is the compound that is capable of controlled and predictable local NO-release. This substance would be able to give a clear answer to the question of how different concentrations of NO affect different biological objects and to allow finding the optimal rate and the required concentration of nitrogen monoxide for a particular physiological effect. [START_REF] Riccio | Nitric Oxide Release Part I. Macromolecular Scaffolds[END_REF] The use of a controlled NO-donor will reduce the dose required for treatment and reduce the side effects associated with the release of nitric oxide beyond the immediate biological target. [START_REF] Nie | Controlled Nitric Oxide Release for Tissue Repair and Regeneration[END_REF] It is clear that controlled release of NO is also extremely important for the effective treatment of cancer with the use of NOdonors, since it significantly reduces the toxic effect of RNS on healthy cells of the body. [START_REF] Xiang | Transition-Metal Nitrosyls for Photocontrolled Nitric Oxide Delivery[END_REF] Another potential use of materials capable of controlled NO-release is the creation of various devices, such as artificial blood vessels or tubes for hemodialysis. [START_REF] Frost | Polymers Incorporating Nitric Oxide Releasing/generating Substances for Improved Biocompatibility of Blood-Contacting Medical Devices[END_REF] One of the main ways of obtaining of such compounds is the design of photoactive NO-donors.

Among the substances that are capable of photoinduced release of NO, the most promising and studied are derivatives of nitrobenzene and metal nitrosyl complexes. However, a large number of works is also devoted to the study of supramolecular ensembles (i.e. liposomes, micelles), nanoparticles and polymer materials that are capable of releasing or activating the NO-donors, which in turn can produce nitric oxide locally. [START_REF] Kim | A Platform for Nitric Oxide Delivery[END_REF][START_REF] Reynolds | Nitric Oxide-Releasing Hydrophobic Polymers: Preparation, Characterization, and Potential Biomedical Applications[END_REF][START_REF] Shishido | Thermal and Photochemical Nitric Oxide Release from S-Nitrosothiols Incorporated in Pluronic F127 Gel: Potential Uses for Local and Controlled Nitric Oxide Release[END_REF][START_REF] Frost | Controlled Photoinitiated Release of Nitric Oxide from Polymer Films Containing S-Nitroso-N-Acetyl-DL-Penicillamine Derivatized Fumed Silica Filler[END_REF][START_REF] Riccio | Photoinitiated Nitric Oxide-Releasing Tertiary S-Nitrosothiol-Modified Xerogels[END_REF] The investigation of aromatic nitrocompounds as NO-donors was started by

NO 2 R R' R = CH 3 , CF 3 , Ar R' = H, CH 3 , CF 3 , Ar F F F N O O
excited states. In this view the process NO-release from o-substituted derivatives of nitrobenzene occurs, probably, through the stage of isomerization of the nitro into the nitrite derivative and the subsequent decomposition of the latter into NO and the phenoxy radical due to O-N bond breakage (Scheme 1.7). [START_REF] Sortino | The Photochemistry of Flutamide and Its Inclusion Complex with Beta-Cyclodextrin. Dramatic Effect of the Microenvironment on the Nature and on the Efficiency of the Photodegradation Pathways[END_REF] According to the authors, the key factor for the possibility of isomerization is the orthogonal arrangement of the nitrogroup and the benzene ring. [START_REF] Hishikawa | Photoinduced Nitric Oxide Release from a Hindered Nitrobenzene Derivative by Two-Photon Excitation[END_REF][START_REF] Fukuhara | Photochemical Generation of Nitric Oxide from 6-Nitrobenzo[a]pyrene[END_REF] Scheme 1.7. The mechanism of nitric oxide release from an anticancer drug flutamide Nitrobenzene-based NO-donors are thermally stable under physiological conditions, and the release of nitric oxide from these compounds can be controlled by electromagnetic irradiation. Also, the advantage of nitrobenzenes as photoactive NO donors is the absence of metal ions, the presence of which could itself provide cytotoxic properties. However, the significant disadvantage of this class of NOdonors is the need to use electromagnetic radiation of UV-region, which is significantly absorbed by biological tissues and fluids and is hazardous to healthy cells.

An example of work aimed at overcoming this lack of nitrobenzenes is the work of Naoki Miyata group. [START_REF] Hishikawa | Photoinduced Nitric Oxide Release from a Hindered Nitrobenzene Derivative by Two-Photon Excitation[END_REF][START_REF] Kitamura | Visible Light-Induced Nitric Oxide Release from a Novel Nitrobenzene Derivative Cross-Conjugated with a Coumarin Fluorophore[END_REF] Modification of the starting 2,6dimethylnitrobenzene (which is responsible for the NO release) by the introduction of a compact fluorophore (such as 7-hydroxycoumarin or 7-aminocoumarin) made it possible to shift the band of absorption of compounds from UV to the visible domain of electromagnetic waves (Figure 1.7a and 1.7b). [START_REF] Kitamura | Visible Light-Induced Nitric Oxide Release from a Novel Nitrobenzene Derivative Cross-Conjugated with a Coumarin Fluorophore[END_REF] An interesting fact was that in the case of a DEAMC-DNB in which there is a complete conjugation of the aminogroup with the nitrogroup through the -chain, release of nitric oxide is not observed under the irradiation of compound at 430-460 nm. Owing to the efficient intramolecular charge transfer, the bond order of C-N(NO2) bond increases to double, and nitro-nitrite isomerization becomes impossible. However, in the case of a compound where the -system cross-conjugation is present (Bhc-DNB), the irradiation results in NO-release. Under excititation of the compound no significant charge transfer occurs in the molecule (as could be concluded from the absence of an intense band in the UV-visible spectrum) and the band 350-430 nm appears due to the absorption of coumarin fragment, which acts as an antenna. Thus the researchers were able to shift the excitation wavelengths required for nitrobenzene activation from UV to visible domain. [START_REF] Kitamura | Visible Light-Induced Nitric Oxide Release from a Novel Nitrobenzene Derivative Cross-Conjugated with a Coumarin Fluorophore[END_REF] Another elegant way to avoid the UV irradiation to initiate NO-release from nitrobenzenes is the use of two-photon absorption method. This approach allows shifting of the excitation wavelength up to the infrared (IR) region, which does not show a deleterious effect on the body and is more permeable for biological tissues.

Binding of 2,6-dimethylnitrobenzene through a styryl and weakly conjugated amide fragment to fluorescein (which is famous for its ability to produce two-photon excited fluorescence [START_REF] Xu | Measurement of Two-Photon Excitation Cross Sections of Molecular Fluorophores with Data from 690 to 1050 Nm[END_REF] ) researchers obtained a Flu-DNB compound (Figure 1.8) that released nitric oxide when irradiated with an IR pulse laser with a wavelength 720-800 nm. The formation of nitrosonium-containing compounds requires the transfer of one electron from nitric oxide to a metal center, followed by -binding andbackbonding interaction d M * (Figure 1.9), and the formation of complexes that could be described as those containing nitroxyl anion is preceded by the transition of the electron from metal to the nitric oxide (Scheme 1.8). 60

-dative interaction -dative interaction

M N O M N O M N O
Thus, in the linear coordination form the oxide acts formally as a donor of 3 electrons, whereas in the angular form it is a donor of 1 electron. Both the method of valence bonds and the method of molecular orbitals showed that the increase in the electron density at the M-N bond due to the backdonation leads to the increase of this bond's order though by reducing the energy of N-O bond.

Due to the discovery of the biological role of nitrogen (II) oxide, the interest in the coordination compounds of this molecule with metals has exponentially increased since the 1980s. [START_REF] Fomitchev | Combined X-Ray Diffraction and Density Functional Study of [ Ni ( NO )( 5 -Cp *)] in the Ground and Light-Induced Metastable States[END_REF] Apparently, the vast majority of compounds have a linear M-N-O fragment.

Complexes in which this angle is much smaller are basically the complexes of the right half of d-metals. An explanation for this lies in the presence of bigger number of electrons at the d-sublevel that reduces the ability of metals to accept three electrons from nitric oxide. But only in this case the linear geometry of the complex is possible. 1 Among the compounds found in CSD, there are also those containing from 2 to 4 NOfragments that can assume either the same or different geometry. [START_REF] Enemark | Principles of Structure, Bonding, and Reactivity for Metal Nitrosyl Complexes[END_REF] Nitric oxide in linear conformation in complexes is a very strong -acceptor.

The use of photoelectron spectral methods allowed to assess the ability of NO and other ligands to withdraw electron density from metal atoms through thebackdonating interaction. [START_REF] Lichtenberger | Relative Bonding Capabilities of Molecules to Metals as Measured by Gas-Phase Photoelectron Spectroscopy[END_REF] Among other ligands, nitrosyl cation occupies leading positions. In particular, its -withdrawing ability is the highest in the following series: [START_REF] Lichtenberger | Relative Bonding Capabilities of Molecules to Metals as Measured by Gas-Phase Photoelectron Spectroscopy[END_REF] Due to the significant shift of the electron density, the M-N distance significantly decreases with increase of d M * dative interaction. For example, in complexes that contain both linearly coordinated nitric oxide and ammonia as ligands, the M-N NO bond length is less than the bond length of M-N NH3 by 0.35-0.4 Å. The values of the M-N bond lengths in complexes indicate that these bonds are covalent for the most part. In view of this, the description of complexes as ionic compounds of nitrosonium-cation or nitroxyl anion becomes less relevant.

NO > CO > 2 -MeC CMe > H 2 C=CH 2 > SO 2 > N 2 > PMe 3 > SiCl 3 > NH 3 > CN > H > Cl > SiMe 3 > C CH
Another approach of describing complexes with non-innocent (redox-active) ligands (one of which is nitric oxide) is the Enemark-Feltman notation. Its advantage is the omitting of the concept of oxidation states of the central atom and ligands. When utilizing the Enemark-Feltman formalism for complexes with nitric oxide, the latter are designated as {M(NO) x } n , where x is the number of NO ligands and n is the total number of electrons located on the d-orbitals of the metal atom and * -orbitals of nitric oxide. It is assumed that the metal atom is in its formal oxidation state, and nitric oxide is neutral. [START_REF] Enemark | Principles of Structure, Bonding, and Reactivity for Metal Nitrosyl Complexes[END_REF] Examples of the use of the (terpy -terpyridine)

Although the description of NO-complexes in this way eliminates ambiguity in determining the oxidation state of central atom and ligands, in some cases assigning a charge to them helps in understanding of electronic and magnetic properties of compounds.

To complete a picture of the coordination capabilities of NO, its ability to act as a bridging ligand should be considered as well. Similarly to the coordination behavior of carbon monoxide, nitric oxide is capable of binding two, three, and in some cases four metal atoms, stabilizing metal cluster complexes (Figure 1.11 O)] + it emulates the nitrite reductase activity (an enzyme consisting of diatomic copper cluster). Indeed, it is known that the main mechanism of this transformation includes the copper-nitrosyl complex as an intermediate stage. [START_REF] Hayton | Coordination and Organometallic Chemistry of Metal-NO Complexes[END_REF]

Study of metal-nitrosyl complexes by means of IR spectroscopy

Modern physicochemical methods allow an accurate characterization of metalnitrosyl complexes; in particular, it is possible to determine the binding parameters and electronic structure of the M-N-O fragment without X-ray diffraction analysis.

However, the interpretation of the obtained spectral data should be carried out with extreme caution and captiousness. In cases of possible ambiguity in the interpretation of certain results, methods of quantum chemistry serve as an auxiliary tool and enable a deeper understanding of the electronic structure of the complex.

The most important and frequently used spectral methods in the study of nitrosyl complexes are IR, EPR, UV and NMR spectroscopy. Less commonly used and more specific methods are the Mössbauer spectroscopy, X-ray (XAS) spectroscopy, magnetic circular dichroism, and the study of magnetic susceptibility. [START_REF] Lewandowska | Spectroscopic Characterization of Nitrosyl Complexes[END_REF] The use of vibrational spectroscopy for the study of nitrosyl complexes has become widely used. In fact, the dependence of the characteristic vibrations of NO on the donor-acceptor properties of the environment can serve as a tool for understanding the nature of the interaction of metal atom with nitric oxide. As indicated in section 1.1, the valence vibrations of free NO radical have a frequency of 1875 cm -1 . After coordination of NO to the metal atom, the value may either increase or decrease depending on different parameters such as the nature of other ligands in the coordination sphere, the electronic configuration of the central atom, the total charge of the complex and its geometry. For metal-nitrosyl complexes there is a general tendency for the increase of vibrations frequency with the increase of the positive charge of nitrosyl ligand from 1300 cm -1 to 1950 cm -1 . 2 In addition, for compounds with linearly coordinated nitric oxide this value lies within the limits of 1950-1450 cm -1 , and for those in which the M-N-O angle is considerably less than 180° vibrations in the region of 1720-1400 cm -1 are more typical; for bridging nitric oxide -from 1650 cm -1 to 1300 cm -1 (Figure 1.12). Nevertheless, if the frequency value is higher than 1750 cm -1 , the linear geometry can be accurately established.

More correct and reliable correlation can be considered for the complexes similar in their electronic structure. For example, if the central atom is represented by one of the transition elements of 8 th group (Fe, Ru, Os), and the complex have the following structure {M(NO)} [6][START_REF] Lewis | Kinetics of the Reaction of Nitric Oxide with Oxygen in Aqueous Solutions[END_REF][START_REF] Wink | The Cytotoxicity of Nitroxyl: Possible Implications for the Pathophysiological Role of NO[END_REF] (by the Enemark-Felthman notation) (Table 1.2). [START_REF] Lewandowska | Spectroscopic Characterization of Nitrosyl Complexes[END_REF] Complex Frequency {M(NO)} 8 1270-1500 {M(NO)} [START_REF] Lewis | Kinetics of the Reaction of Nitric Oxide with Oxygen in Aqueous Solutions[END_REF] 1600-1700 {M(NO)} 6 1800-1960 Table 1.2. Valence vibrations of N-O in complexes of metals of the 8 th group metals.

As it was mentioned, the frequency of the valence vibrations of nitric oxide in complexes depends on many factors (in particular, on the nature of other ligands present in the complex). In the work of De La Cruz and Sheppard, authors made an attempt to summarize the effects of other ligands on the variation of the frequency of the vibration of the N-O bond. [START_REF] De La Cruz | A Structure-Based Analysis of the Vibrational Spectra of Nitrosyl Ligands in Transition-Metal Coordination Complexes and Clusters[END_REF]

Ruthenium-nitrosyl complexes as NO donors

The idea of utilizing of metal complexes as NO-donors falls in line with the fact that the primary goal for the attack of NO in the human body is iron-containing enzymes. [START_REF] Huerta | Nitric Oxide Donors : Novel Cancer Therapeutics ( Review )[END_REF] Among the coordination compounds with nitric oxide donating ability sodium nitroprusside (SNP) is the most studied and well known one. More than for 90 years SNP is used for medical purposes as a hypotensive drug of the class of vasodilators. In the solid state Na 2 [Fe(CN) 5 NO]•2H 2 O can be stored for years in the absence of light and moisture, but in the solution the compound becomes extremely photosensitive and reactive to oxygen. [START_REF] Wang | Nitric Oxide Donors: Chemical Activities and Biological Applications[END_REF] The mechanism of NO release from SNP in vivo is not yet fully understood, but this process is thought to be initiated by photoexcitation or one-electron reduction, and the presence of thiols accelerates it (Scheme 1.9). 44

Scheme 1.9 Possible mechanisms for the release of nitric oxide from SNP

As can be seen from the scheme, the process of reduction and subsequent decomposition of SNP is accompanied by the release of cyanide anion (sometimes up to 5 equivalents in biological conditions) [START_REF] Wang | Nitric Oxide Donors: Chemical Activities and Biological Applications[END_REF] ; this can lead to significant toxic effects on the whole body if significant amount of SNP was used. Also, the spontaneous decomposition of the compound increases the local concentration of the cytotoxic peroxynitrite anion. But, although SNP has some deleterious effects, its use as a vasodilating agent is justified, since the use of even small amounts of the drug is often enough to provoke biological effects. However, the use of this compound is very limited, and the search for new cooordination compounds that would be devoid of these shortcomings is a topical issue.

Among other metals, ruthenium attracts attention due to its ability to emulate the coordination features of iron. 2 Unlike the latter, the ruthenium complexes are always low-spin ones, both in the oxidation states +3 or +2, which contributes to their higher stability compared to iron complexes, as well as the lower lability of the ligands (including nitric oxide) in its coordination environment; [START_REF] Ford | Photochemistry of Metal Nitrosyl Complexes. Delivery of Nitric Oxide to Biological Targets[END_REF][START_REF] Rose | Lux: Selective Delivery of High Flux of Nitric Oxide (NO) to Biological Targets Using Photoactive Metal Nitrosyls[END_REF] this is a prerequisite for their biological application. Confirmation of this can be a found in comparison of SNP with its Ruthenium analogue [Ru(CN) 5 NO] 2-. Like sodium nitroprusside, [Ru(CN) 5 NO] 2-is capable of being excited with electromagnetic waves, but unlike SNP, this compound does not release toxic cyanide ions in solution. [START_REF] Hayton | Coordination and Organometallic Chemistry of Metal-NO Complexes[END_REF] Ruthenium-nitrosyl complexes also have several advantages, which are often not typical for coordination compounds of other metals -good water solubility, resistance to air oxidation and low cytotoxicity. [START_REF] Huang | Nitric Oxide Donor-Based Cancer Therapy: Advances and Prospects[END_REF] The kinetics of ruthenium interaction with bioligands is often compared to the effects caused by platinum on the body; 75 however, numerous studies indicate a significantly lower toxic effect of ruthenium, which may be due to its close to iron coordination behavior and its ability to bind albumin molecules and iron-transporting transferrin proteins. [START_REF] Tfouni | Biological Activity of Ruthenium Nitrosyl Complexes[END_REF] Depending on the type of ligands in the coordination sphere, ruthenium can exhibit several basic oxidation levels that can exist in the biological environment -Ru(II), Ru(III) and Ru(IV). In the presence of reducing agents as glutathione or ascorbate Ru(III) could easily be reduced to Ru(II). Coordination compounds in which ruthenium is in the oxidation state +2 are more susceptible to ligand exchange and readily interact with N-donor or S-donor biomolecules. [START_REF] Wang | Nitric Oxide Donors: Chemical Activities and Biological Applications[END_REF] By changing the donoracceptor properties of the ligands (i.e. their ability to -binding) the energy and strength of the bond Ru-N NO in the ruthenium-nitrosyl complexes can be varied affecting the efficiency and rate of nitric oxide release. [START_REF] Wang | Nitric Oxide Donors: Chemical Activities and Biological Applications[END_REF] An important advantage of ruthenium (along with Mn and Fe) in comparison with other metals is the photoactivity of its nitrosyl complexes. Despite the high stability of the coordination compounds of ruthenium with nitrogen monoxide, they are capable of releasing NO under irradiation by electromagnetic waves of a certain length. [START_REF] Xiang | Transition-Metal Nitrosyls for Photocontrolled Nitric Oxide Delivery[END_REF] Due to this feature ruthenium-nitrosyl complexes are intensively studied for the purpose of obtaining the NO-donor capable of local, time-controlled, photosensitive release of nitric oxide.

The first studies of NO-release from ruthenium-nitrosyl complexes under the influence of light were carried out on {Ru(NO)} 6 compounds with monodentate ligands -mainly amines and halogens (Figure 1.13).

The investigation of nitric oxide photorelease and the nature of corresponding photoproduct was carried out in 1983 by Sinitsyn and his collaborators; in this case the compound K 2 [RuCl 5 (NO)] was chosen as NO-donor. The signal observed in EPR spectroscopy during the experiment of photorelease having g-factor equal to 2.34 denoted the presence of paramagnetic low-spin d 5 -Ru(III) particles in the solution. [START_REF] Rose | Photoactive Ruthenium Nitrosyls: Effects of Light and Potential Application as NO Donors[END_REF] The anion of The quantum yields ( ) found for compounds K 2 [RuCl 5 (NO)] and RuNOCl 3 are 0.06 and 0.012 respectively. [START_REF] Bettache | Photolabile Donors of Nitric Oxide: Ruthenium Nitrosyl Chlorides as Caged Nitric Oxide[END_REF] This difference in the values for two quite similar compounds arises from the fact that the presence of a greater number of negatively charged ligands (5 chlorine atoms per ruthenium atom in the first compound against 3 chlorine atoms in the second) facilitates the process of NO-photorelease. Today these compounds are well studied and are commercially available. [START_REF] Rose | Photoactive Ruthenium Nitrosyls: Effects of Light and Potential Application as NO Donors[END_REF] Studies of analogous compounds in which chlorine atoms in the equatorial plane are replaced with ammonia molecules -trans-[Ru(NH 3 ) 4 (X)(NO)] 3+ -have shown that the ligand that is in the trans-position to nitric oxide has a significant effect on the rate and efficiency of NO-release. Thus, in the case of the phosphite P(OEt) 3 ligand the quantum yield of NO-release was = 0.3, while for the compound with the imidazole ligand in the trans-position to NO this value was only 0.04. [START_REF] Rose | Photoactive Ruthenium Nitrosyls: Effects of Light and Potential Application as NO Donors[END_REF] Giving preference to polydentane ligands over monodentate ones in the study of compounds for the purpose of their further use for medical purposes is determined by a greater stability of chelating complexes and complexes with macrocyclic ligands. [START_REF] Rose | Photoactive Ruthenium Nitrosyls: Effects of Light and Potential Application as NO Donors[END_REF] The necessity of using complexes with high stability constants becomes clear if we take into account the infinite number of biomolecules in the body that can strongly bind metal atoms, competing with monodentate ligands. Thus, polydentane ligands make it impossible to bind metals with bioligands, thus reducing or eliminating the harmful effects of the former; [START_REF] Rose | Photoactive Ruthenium Nitrosyls: Effects of Light and Potential Application as NO Donors[END_REF] and also, which is important for photoactive compounds, polydentate ligands provide the stability of complexes, and therefore thir photochemical characteristics.

Since prosthetic groups of heme proteins (hemoglobin, sGC, cytochromes) are the primary targets for nitric oxide attack in the body (see section 1.2), one of the first attempts to receive NO-donor based on coordination compounds of ruthenium with polydentane ligands was made precisely with the use of porphyrins. [START_REF] Rose | Lux: Selective Delivery of High Flux of Nitric Oxide (NO) to Biological Targets Using Photoactive Metal Nitrosyls[END_REF] The resulting compounds of the general formula [(P)Ru(NO)Cl], where P is porphyrin, were thermally more stable and less susceptible to oxidation by oxygen in the absence of irradtiation than similar iron complexes. However, the reverse recombination of released NO molecule was too fast (k 1*10 8 M -1 s -1 ), that made these compounds unsuitable for targeted NO delivery. [START_REF] Xiang | Transition-Metal Nitrosyls for Photocontrolled Nitric Oxide Delivery[END_REF][START_REF] Rose | Lux: Selective Delivery of High Flux of Nitric Oxide (NO) to Biological Targets Using Photoactive Metal Nitrosyls[END_REF][START_REF] Lorkovi | Kinetics and Mechanism of Nitric Oxide Disproportionation upon Reaction with Ruthenium(II) Porphyrin Carbonyls: Evidence for Dinitrosyl Intermediates[END_REF] More promising from a practical point of view are non-porphyrin-type ligands The study of the NO-release from these compounds under irradiation ( = 365 nm) showed a certain dependence on the nature of the solvent in which the process took place. Donor solvents such as acetonitrile have been shown to be able to stabilize the generated photoproduct, and the reverse process of the released NOmolecule coordination is relatively slow (k 10 -2 -10 -4 M -1 s -1 ). [START_REF] Rose | Photoactive Ruthenium Nitrosyls: Effects of Light and Potential Application as NO Donors[END_REF] If tetrahydrofuran (THF) or toluene (PhMe) is used instead of acetonitrile the process of photo-release is immediately followed by a very rapid recombination. with this ligand (Figure 1.16) occurs with deprotonation of the nitrogen atom of the carboxamide group. Thus, in the formed complex the negatively charged nitrogen atom acts as -donor in the trans-position to the nitrosyl ligand.

Such an important nuance in the structure of the complex makes the compound stable in an aqueous medium at pH ranging from 5 to 9, despite the fact, that vast majority of ruthenium-nitrosyl coordination compounds undergo the transformation into nitrite form at pH>5: [START_REF] Rose | Photoactive Ruthenium Nitrosyls: Effects of Light and Potential Application as NO Donors[END_REF] Ru-NO + H 2 O Ru-NO 2 + 2H +

The absence of this transformation even in the presence of hydroxide anions indicates that a strong -donor ligand in the trans-position to nitric oxide in the {RuNO} 6 complex protects the NO-group from the nucleophilic attack.

Along with the high stability of [(PaPy 3 )Ru(NO)] 2+ in solution, the compound also exhibits good photochemical properties. Nitric oxide is easily released from the compound ( = 0.05), and the process of reverse recombination is not observed. [START_REF] Rose | Photoactive Ruthenium Nitrosyls: Effects of Light and Potential Application as NO Donors[END_REF] These parameters (stability and NO-release ability) make the compound interesting in terms of its direct use in biological research. Successful attempts to use [(PaPy 3 )Ru(NO)] 2+ for the transport of NO to myoglobin and cytochrome oxidase are described by Mascharak group. [START_REF] Szundi | Rapid Communication A New Approach for Studying Fast Biological Reactions Involving Nitric Oxide : Generation of NO Using Photolabile Ruthenium and Manganese NO Donors[END_REF] Many works have recently been aimed at finding ways to sensitize rutheniumnitrosyl complexes in the visible and infrared domains of light. For the purpose of the bathochromic shift of the transition d (Ru) -*(NO), Mascharak group attempted to attach the ruthenium-nitrosyl complex to a molecule of a dye that absorbs light in the visible domain. Resorufin (Resf) and fluorescein derivatives (FlEt) were used as such molecules (Figure 1.17). (390-400 nm), for compounds 1-Resf and 1-FlEt these values are 500 nm and 475 nm respectively. At the same time, the alteration of the donor atom exclusivelysubstitution of chlorine atom with the oxygen atom (in the comlex [Ru(OH)(Me 2 bpb)NO] (abbreviated 1-OH)) -does not significantly affect the shift of max . [START_REF] Rose | Sensitization of Ruthenium Nitrosyls to Visible Light via Direct Coordination of the Dye Resorufin : Trackable NO Donors for Light-Triggered NO Delivery to Cellular Targets[END_REF] The release of NO from these compounds under irradiation showed not only their ability to be effectively sensitized in the visible region, but also revealed the unique ability of these complexes. The presence of molecules capable of luminescence in their structure, provided a tool for the NO-release control.

Interestingly, the compound 1-Resf is fluorescent, in contrast to 1-FlEt. [START_REF] Rose | Sensitization of Ruthenium Nitrosyls to Visible Light via Direct Coordination of the Dye Resorufin : Trackable NO Donors for Light-Triggered NO Delivery to Cellular Targets[END_REF][START_REF] Fry | Triggered Dye Release via Photodissociation of Nitric Oxide from Designed Ruthenium Nitrosyls : Turn-ON Fluorescence Signaling of Nitric Oxide Delivery[END_REF] Fig. 1.18 Electronic spectra of ruthenium nitrosyl complexes with dyes: a) comparison of the free resorufin spectrum with the spectrum of the 1-Resf complex and the 1-OH complex; 2) comparison of the spectrum of the 1-FlEt complex with the spectrum of the 1-Cl complex But the situation changes to the opposite at the moment of NO-release. The photoproduct produced from compound 1-Resf does not show fluorescence, that caused by the presence of a paramagnetic d 5 -Ru(III)-center. [START_REF] Fry | Triggered Dye Release via Photodissociation of Nitric Oxide from Designed Ruthenium Nitrosyls : Turn-ON Fluorescence Signaling of Nitric Oxide Delivery[END_REF] In the case of 1-FlEt irradiation of the compound is accompanied with a liberation of a nitric oxide molecule and a molecule of a dye (Fig. 1.19), that restores its intense emission in a free state. These studies indicate the possibility of shifting the absorption band of ruthenium-nitrosyl complexes into visible region and exemplify the release of NO when these compounds are irradiated with waves of this domain.

Another widely used ligand for synthesis of ruthenium-nitrosyl complexes is terpyridine. As with other polypyridyl complexes, ruthenium compounds with terpyridine exhibit high stability. In addition to the chelate effect of terpyridine, the high stability of these complexes is supported by a significant d-* backdonating interaction. [START_REF] Schubert | Chemistry and Properties of Terpyridine Metal Complexes[END_REF] An intensive study of ruthenium-nitrosyl complexes with these ligands was performed by Roberto Santana da Silva and Isabelle Malfant groups.

The use of terpyridine ligand in ruthenium nitrosyl complexes leaves two of the coordinating positions in the polyhedra of ruthenium free. Consequently, these positions may be occupied by either two monodentate ligands (amines, ammonia, halogens, etc.) or bidentate ligand.

In the year 2014 the group of I. Malfant obtained ruthenium-nitrosyl complexes with terpyridine ligand and two chloro-ligands (Figure 1.20). 86 The separation of these complexes was carried out using the method of high-performance liquid reverse-phase chromatography (HPLC). The frequency of the NO vibrations in IR spectroscopy was proposed for the distinction of isomers: for the trans-isomer (the nitrosyl moiety is in the trans-position to the pyridine ring of terpyridine) this value is 1901 cm -1 , and for the cis-isomer (nitrosyl in trans-position to chloro-ligand) -1894 cm -1 . [START_REF] Akl | Comparative Photo-Release of Nitric Oxide from Isomers of Substituted terpyridinenitrosylruthenium(II) Complexes: Experimental and Computational Investigations[END_REF] The electronic spectra of the two complexes are similar, although for the transisomer ( max = 414 nm), the lowest transition is shifted by an energy of 0.2 eV into the visible region (for the cis-isomer max = 389 nm).

Quantum-chemical calculations with the use of that is poorly permeable into biological objects.

The confirmation of nitrogen monoxide release in this work was done with the use of indirect method -the Griess test, which consists in the photometric determination of pink diazo-dye ( max = 548 nm), which is formed as a result of the reaction of nitrite anions (formed as a result of oxidation of NO in solution) with sulfanilic acid. [START_REF] Tsikas | Analysis of Nitrite and Nitrate in Biological Fluids by Assays Based on the Griess Reaction: Appraisal of the Griess Reaction in the L-Arginine/nitric Oxide Area of Research[END_REF] Another, more reliable direct method for the determination of nitric oxide is the use of iron-N-methyl-D-glucamine dithiocarbamate (Fe(MGD) 2 ) as a specific spin trap for nitric oxide with further determination of the Fe(MGD) 2 -NO complex by EPR spectroscopy. [START_REF] Vanin | Why Iron-Dithiocarbamates Ensure Detection of Nitric Oxide in Cells and Tissues[END_REF] As an example of terpyridine ruthenium-nitrosyl complexes, the coordination sphere of which is complemented with the bidentate ligand, we can also cite the compounds synthesized by Liu's group.

In order to integrate the ruthenium-nitrosyl complex into nanoparticles for subsequent NO targeted delivery into biological objects, the terpyridine ligand has been functionalized with the carboxyl group, which will enable covalent binding of the NO donor to "nano-carriers", in particular TiO 2 . The photosensitization of the obtained compound in the visible region of the spectrum was done by attachment of the DAMBO dye (8-(3,4-diaminophenyl)-4,4difluoro-1,3,5,7-tetramethyl-4-boron-3a, 4a-diaza-s-indacene) directly to the metal center. The resulting complex [Ru(tpy COOH )(DAMBO)NO](PF 6 ) 3 integrated on the TiO 2 surface was stable in the absence of light and was capable of releasing nitric oxide when irradiated. [START_REF] Xiang | Transition-Metal Nitrosyls for Photocontrolled Nitric Oxide Delivery[END_REF][START_REF] Xiang | Photo-Controlled 194 Targeted Intracellular Delivery of Both Nitric Oxide and Singlet Oxygen Using a Fluorescence-Trackable Ruthenium Nitrosyl Functional Nanoplatform[END_REF] An interesting feature of this complex is the ability to generate both NO and singlet oxygen 1 O 2 when irradiated with visible light; this is the first example of compounds capable of releasing both particles that play a key role in photodynamic therapy. [START_REF] Xiang | Photo-Controlled 194 Targeted Intracellular Delivery of Both Nitric Oxide and Singlet Oxygen Using a Fluorescence-Trackable Ruthenium Nitrosyl Functional Nanoplatform[END_REF] Thus, the use of terpyridine for the strong binding of

Mechanism of nitric oxide release from ruthenium-nitrosyl complexes: theoretical studies

A detailed theoretical study of the release of NO from ruthenium-nitrosyl polypyridyl complexes was carried out by Juan Sanz Garcia. [START_REF] García | Is Photoisomerization Required for NO Photorelease in Ruthenium Nitrosyl Complexes?[END_REF] The theory developed by J. Garcia In the solid state, the transition from one of them to another occurs when the complex is irradiated by electromagnetic waves of different lengths (Fig. 1.26). [START_REF] Cormary | Structural Influence on the Photochromic Response of a Series of Ruthenium Mononitrosyl Complexes[END_REF] According to the results of theoretical studies, the release of nitric oxide from ruthenium-nitrosyl complexes is preceded by isomerization of the latter. an overcoming of the energy barrier of 0.67 eV, which in principle is the limit of the possible vibrational activation of the molecule at 3 GS-level (process d); an alternative to this transition can be a direct intersystem crossing from the excited triplet state T n (transition e). Further isomerization requires a transition to the triplet state 3 MS2, from which, through j and k transitions that do not require additional activation, the molecule could isomerize to the isonitrosyl complex (MS1). The presence of a deep potential hole (an energy barrier of 0.73 eV) in the state MS2 makes it impossible to switch to a triplet state by thermal activation. Therefore, the most probable mechanism for overcoming such a barrier is photoexcitation.

The absorption of a photon transfers the molecule into a singlet excited state (process g), from which the 3 MS2 triplet level population occurs as a result of intersystem crossing (process h) and subsequent internal conversion (process i). 93 It should be noted that the magnitudes of the energies corresponding to the phototransitions a and g are very close. Calculated electronic spectra using a timedependent density function theory (TDDFT) for all three isomers are shown in Figure 1.27.

As can be seen from the compounds spectra, electromagnetic irradiation with a 473 nm wavelength is absorbed by both GS and MS2 isomer. In this case, the Fig. 1.27 Electronic spectra of all three GS, MS1 and MS2 isomers calculated using TDDFT isonitrosile complex (MS1) is not excited by the light of such energy ( 0). From experimental studies it is known that isomerization of the nitrosyl complex [RuCl(NO)(py) 4 ] 2+ occurs when it is irradiated with wavelength = 473 nm. In view of the isomerization mechanism, we can say that the use of light for this process leads to the absorption of two photons instead of only one that eventually leads to the population of an unstable 3 MS, from which the molecule transforms into isonitrosyl complex. At the same time the photons of this energy are not absorbed by the MS1 complex. However, under irradiation with the red light the resulting isonitrosyl complex isomerizes into the starting ruthenium complex, which does not absorb light of this wavelength domain.

According to the study, reaching of the 3 MS2 level is important not only for the isomerization process, but also for the release of nitric oxide from the complex. In previous works (Bitterwolf et al. [START_REF] Bitterwolf | Photolysis of [Ru(bipy)2(NO)Cl](PF6)2 in Frozen Ionic Glass Matrices. Evidence for Nitrosyl Linkage Isomerism and NO-Loss in a Physiologically Relevant Nitric Oxide Source[END_REF] , Woike et al. [START_REF] Giglmeier | Nitric-Oxide Photorelease and Photoinduced Linkage Isomerism on Solid [Ru(NO)(terpy)(L)]BPh4 (L = Glycolate Dianion)[END_REF] ) attention has already been paid to the importance of linkage isomers in the process of NO-release from rutheniumnitrosyl complexes.

An attempt to explain the inclinations of the ruthenium-nitrosylcomplexes either to isomerization or the release of NO based on the structure of complexes was made in the work of García et al. [START_REF] García | Is Photoisomerization Required for NO Photorelease in Ruthenium Nitrosyl Complexes?[END_REF] It is noteworthy that the proposed mechanism and the explanation for different values of quantum yield for NO-release is consistent with experimental data obtained in various scientific groups. When the compound transit to the 3 MS2 triplet state its further transformation can take place in two ways:

isomerization with the formation of the MS1-isomer or the release of NO. The competition between them is determined by the kinetics of both processes or rather by the difference between the energy of the dissociation D e2 and the energy barrier that must be overcome for isomerization (Figure 1.11).

Thus, when D e2 < 3 B2, the release of nitric oxide occurs easier, otherwise the complexes are more prone to isomerization.

In summary, we can say that, like the process of isomerization, the process of NO-release from ruthenium-nitrosyl complexes occurs as a result of absorption of two photons. In this case, as a result of several electronic transitions, the molecule transits to a triplet state, and then, depending on the relation between the dissociation energy and the isomerization energy, both the NO-release and the isomerization with the formation of the isonitrosyl complex can take place.

Two-photon absorption as a method of photosensitization of compounds within the therapeutic window

The two-photon absorption phenomenon was predicted by Maria Göppert-Mayer [START_REF] Göppert-Mayer | Uber Elementarakte Mit Zwei Quantensprüngen[END_REF] in 1931, although it was practically observed for the first time only 30 years later by Kaiser and Garrett. [START_REF] Kaiser | Two-Photon Excitation in CaF2:Eu2+[END_REF] The TPA process is the excitation of a molecule, which occurs when absorbing not one, as in the case of linear absorption, but two photons (must not be confused with the mechanism described in 1.4.4, which includes two separate steps of absorption of photons). The process of absorption of two photons occurs simultaneously, but it is still considered that the transition to a "stable" excited state is preceded by the transition to the so-called "virtual level" when molecule absorbed one of two photon (Scheme 1.12). and quadratically depends on the intensity of the exciting radiation. [START_REF] Belfield | Synthesis of New Two-Photon Absorbing Fluorene Derivatives via Cu-Mediated Ullmann Condensations[END_REF] Two-photon absorption (TPA) is a third ofder nonlinear optical phenomenon. [START_REF] Przhonska | Two-Photon Absorption in Near-IR Conjugated Molecules: Design Strategy and Structure-Property Relations[END_REF] It is possible to describe the response of a substance on the action of light using the dependence of the macroscopic polarization P on the intensity of the electric field E: P = P (1) + P (2) + P (3)

+ … = 0 ( (1) E + (2) E + (3) E + …),
where 0 is the dielectric constant in a vacuum, P (n) is the polarization of the n th order, (n) is the optical susceptibility of the n th order; while (1) describes the linear properties of the materials, (2) is an important parameter for the phenomena of the second harmonic generation, sum-frequency generation etc. The third-order susceptibility (3) is associated with such phenomena as generation of the third harmonic, nonlinear refraction, two-photon absorption and others.

When light passes through substances capable of one-(OPA) and two-photon absorption (TPA), its intensity I(z) change as follows:

where and are the coefficients of one-and two-photon absorption of the medium, respectively. The index z indicates the propagation of light along the conventional axis z in the medium. In the case when the substance does not exhibit linear absorption of the light, and only two-photon absorption is present, the expression simplifies to the next form: 100 Scheme 1.12 Schematic comparison of one-(OPA) and two-photon (TPA) absorption processes .

The physical interpretation of this expression is that the magnitude of the two-photon absorption is proportional to the square of the intensity of light. The solution of this differential equation is:

In this expression, I 0 is the initial intensity of the exciting radiation, z is the thickness of the medium layer in which light propagation occurs. ( ) is a macroscopic parameter, which depends on the concentration of molecules capable of two-photon absorption, and can be represented in the following form: 100 where c is the concentration of the photoactive substance, N A is Avogadro number, h is Planck's constant, is the frequency of the light, and is the two-photon absorption cross-section. is a parameter that characterizes the intensity of the absorption of two photons by a molecule. As a unit of measure for it is common to use cm 4 •s. But since the values of in practice vary within 10 -51 -10 -46 cm 4 •s, a special unit of measurement GM (from the name of Maria Göper-Meyer) was introduced for convenience:

1 GM = 10 -50 m 4 • Two-photon absorption is a modern, promising tool for in vivo photoactivation of biologically active substances, in particular recent researches are devoted to the design of nitric oxide donors with high TPA cross-sections. 101 The reason for such an interest in this method of activation is the benefits of the TPA. The main advantage of using the TPA approach is the possibility to activate the compounds with electromagnetic radiation in the "therapeutic window" area. Most donors of nitric oxide known today have an absorption maximum in the visible or near UV region. [START_REF] Xiang | Transition-Metal Nitrosyls for Photocontrolled Nitric Oxide Delivery[END_REF][START_REF] Hishikawa | Photoinduced Nitric Oxide Release from a Hindered Nitrobenzene Derivative by Two-Photon Excitation[END_REF] Waves of such lengths are poorly permeable in the biological environment and, in the case of UV radiation, can cause significant negative effects. An effective extinction coefficient of biological tissues against the wavelength is shown in figure 57 1.28 in a pink color. The range of wavelengths of 700-1100 (1300) nm 102 is called "therapeutic window"; waves of this region are the most permeable in the biological environment. According to the scheme 1.12, in the case of TPA, the transition energy S 0 S n is divided into two photons, for example, if the excitation of a molecule in a single-photon process requires the use of a wave with = 400 nm, in the case of TPA the wavelength will be twice as large as 800 nm. Thus, the activation of the compound becomes possible under irradiation with electromagnetic waves of therapeutic window. Another important advantage of using TPA is the accurate localization of the effect on the biological object, which is the result of the quadratic dependence of the two-photon absorption on the intensity of the applied irradiation. From figure 1.29 it is clear that in the case of TPA, the excitation of a photoactive substance takes place in a small volume around the focus of the laser radiation source -this is where the necessary "concentration" of photons is attained, and where the phenomenon of TPA becomes possible. As noted in Chapter 1, the presence of monodentate ligands in the complexes is generally undesirable when designing drugs. The alternative proposed in this work for chloro-ligands is 2,2'-bipyridine. The choice of this ligand is justified by several factors: (i) higher stability of such complex in the biological environment due to increased thermodynamic stability of the {Ru(tpy)bpyNO} complex compared to {RuCl 2 (tpy)NO}; (ii) eliminating the need for a painstaking and complex process of separating the mixture of cisand trans-isomers when monodentate ligands are present; (iii) the potentially higher ability of the compound with 2,2'-bipyridine to participate in two-photon absorption process (TPA). The last statement needs a more detailed explanation.

First, the very presence of an additional fragment with a long chain of conjugation in the compound can lead to an increase of its ability to undergo twophoton absorption. Another argument favoring the idea of increasing the TPA cross section ( ) when introducing 2,2'-bipyridine into the complex is the results of the quantum-chemical calculations performed for these compounds, in particular the calculated angles between the mean plane of the fluorenyl fragment and the mean plane of terpyridine. According to the DFT calculations in a row of trans1-cis1-bpy1 (where bpy1 is a complex in which two chloro-ligands are replaced by a 2,2'bipyridine molecule) the angle between the planes decreases (Table 2.1). This could be explained from the point of view that removing of two negatively charged chloroligands will necessarily increase the withdrawing effect of {Ru(tpy)NO} moiety.

Moreover, inserting of -accepting fragment (2,2'-bipyridine) will increase this withdrawing effect, thus the fluorene moiety will be more effectively conjugated with terpyridine fragment. The values of max obtained theoretically using the time-dependent theory of density functional (TD-DFT) do not differ significantly from the experimental data:

the experimental values of energies are shifted by less than 3000 cm -1 . Nevertheless, in both cases, there is a tendency toward a bathochromic shift and a decrease in the absorption rate in a series of cis1-trans1-bpy1 (Table 2 Expectedly, the energy of these transitions decreases in a row cis1-trans1-bpy1, which is antibate to the change of max in experimental UV-visible spectra of compounds. A more detailed description of electronic transitions with the electron density transfer toward {Ru-NO} fragment calculated by TD-DFT methods is presented in Table 2 Neither of the terpiridine {Ru-NO} complexes obtained in this work nor of the similar complexes obtained in the group of I. Malfant exhibits luminescence. None of coordination compounds obtained at intermediate stages of the synthesis of final {Ru-NO} complexes exhibits luminescence either. Moreover, as noted in chapter 1, the introduction of typical fluorescent dyes in the nitrosyl complexes completely quenches the fluorescence of the first ones, or at least sharply decreases its intensity as in the case of complexes with resorufin and fluorescein derivatives (paragraph 1.4.3). [START_REF] Rose | Sensitization of Ruthenium Nitrosyls to Visible Light via Direct Coordination of the Dye Resorufin : Trackable NO Donors for Light-Triggered NO Delivery to Cellular Targets[END_REF][START_REF] Fry | Triggered Dye Release via Photodissociation of Nitric Oxide from Designed Ruthenium Nitrosyls : Turn-ON Fluorescence Signaling of Nitric Oxide Delivery[END_REF] An explanation for such a phenomenon can be found in the structure of the energy levels of polypyridyl ruthenium complexes. Let's consider the main transitions that occur in the complex upon its excitation using as an example the substance [RuCl(py) 4 NO] 2+ investigated theoretically by J. Garcia. 108 The absorption of a certain energy photon excites the compound to one of the excited singlet energy levels, which, undergoing the internal conversion, passes to the lowest excited level As noted above, a study of the release of nitric oxide from the compounds cis1 and trans1 published by the research group of I. Malfant revealed quite good quantum yields for these complexes, [START_REF] Akl | Comparative Photo-Release of Nitric Oxide from Isomers of Substituted terpyridinenitrosylruthenium(II) Complexes: Experimental and Computational Investigations[END_REF] which are of the same order with those of the terpyridine complexes with similar structure obtained in the group of da Silva. 110 The absence of such transitions in the spectrum of the photoproduct obtained by photolysis of bpy1 may indicate the formation of a diamagnetic complex -Ru II -complex. 107 Perhaps, the photoproduct formed after NO-release, containing Ru III , is instantaneously reduced in solution, and the only compound observed as a photoproduct is [Ru II (FT)bpy(CH 3 CN)] 2+ . The presence of distinct isosbestic points in a series of spectra obtained during the process of nitric oxide photorelease (Figure 2.6c) speaks in support of such a theory.

Investigation of two-photon absorption of cis2, trans2 and bpy2

compounds.

The first attempt to measure the two-photon absorption of cis1 and trans1 compounds was unsuccessful due to insufficient solubility of both complexes in Today, there are two main methods for determining the TPA cross-section :

z-scan and the two-photon-excited fluorescence (TPEF) method yet there are others, for example the method of thermal lens and photo-acoustic methods. 104 Although the most sensitive among them is TPEF, its use is limited to cases of fluorescence compounds. Z-scan is a direct method to determine the nonlinear absorption in bulk materials consists in monitoring the transmittance of the sample under test as a function of the incident intensity of a laser beam. In the practice this is achieved by changing the position (Z coordinates) of the sample in the vicinity of a focal plane of the radiation source. A more detailed description of the z-scan method is given in the experimental part.

The study of two-photon absorption of compounds was carried out using a femtosecond laser radiation source. The use of short-pulse radiation excludes other nonlinear optical phenomena that can significantly overestimate the value of the cross-section TPA . In particular moving from femtosecond to nanosecond lasers in the TPA study may increase the measured hundreds of times due to undesirable additional absorption of excited levels. 100,104,107 As noted above, from absorption spectra of cis1 and trans1 and TDDFT analysis of their excited states it can be seen that the electronic transition that initiates the transfer of the electron density from the fluorenyl substituent onto {Ru-NO} fragment has an energy of about 3 eV corresponding to the energy of electromagnetic radiation with a wavelength of about 400 nm (Figure 2.3). The use of two-photon absorption reduces the energy of exciting radiation and makes possible switching from 400 nm to 800 nm.

In spite of the fact that the corresponding band in the UV-visible spectrum of the bpy1 compound is shifted bathochromically to 450 nm (corresponding to 900 nm in TPA process) compared with derivatives with chloro-ligands, the study of TPA of its analog bpy2 was also carried out at a wavelength of 800 nm. The reason for such a choice is the practical aspects of the use of TPA. In the biophotonics the most promising is the use of wavelengths of 700-900 nm, 107 but obtaining radiation with a wavelength of 800 nm is much simpler and cheaper. In fact, the TPA study requires the use of a Ti-Sapphire laser (Ti:Sa), and the peak intensity of such an oscillator is just at 800 nm.

For comparison we still carried out a TPA study at 900 nm for bpy2, but as will be shown below there was no significant difference between the values of 900 and 800 .

The research was conducted at different laser irradiation intensities. The energy of electromagnetic radiation pulses varied from 30 nJ to 95 nJ. For the three investigated compounds at different intensities of irradiation symmetric z-scan curves were observed, that is an important characteristic as it confirms the absence of other potential nonlinear optical phenomena that often appear at higher energy of light Taking into account the measurement error, we can say that the obtained values of have the same order and fall in the region of 100 GM, with some tendency to increase the efficie ncy of the TPA in the series trans2 <cis2 <bpy2.

Investigation of the compound bpy2, however, requires some additional explanation. Since the absorption band in the electronic spectrum of this compound is shifted by about 2500 cm -1 bathochromically and is at 450 nm, it seems more logical to undertake TPA studies at 900 nm. But it is important to keep in mind that the spectrum of two-photon absorption of compounds can differ significantly from the spectrum of single-photon absorption, although for compounds with a strictly linear structure it's less common. In this regard, moving to 900 nm for TPA does not necessarily have to increase the absorption cross-section . And, as noted above, another advantage of using a laser irradiation of 800 nm is its low cost and ease of obtaining. Nevertheless, we analyzed the ability of the compound bpy2 to the TPA upon the excitation with 900 nm waves. However, there was no significant change in the -value (Table 2.4).

The obtained values of nonlinear optical parameters for compounds cis2, trans2 and bpy2 are close to those published in literature where the donating fragment is represented by fluorene fragment. 107 These values are also close to the nonlinear parameters of typical push-pull molecules, in particular, 4-dialkylamino-4'nitrostilben (DANS, = 88 GM), disperse red ( = 110 GM). However the obtained complexes possess a considerably lower capability of participating in TPA regarding to the highest known among the ruthenium complexes. In particular, for one of the ruthenium coordination compounds -tris(bipyridyl) complex, in which the ligands contain donating dibutylaminophenylvinyl substituents -this value is 2200 GM. But the comparison of the complexes cis2, trans2 and bpy2 with this type of compounds may be somewhat incorrect because of their substantially different structure. Thus, the high value of for the described tris(bipyridyl) ruthenium complex is likely to be due to its octupolar structure and to the presence of strong donating substituents in bipyridyl ligands. 113 Thus, we have proposed a new nitric oxide donor -[Ru II (FT)(bpy)(NO)] (PF 6 ) 3 , which has several advantages over previously known [Ru II (FT)Cl 2 (NO)](PF 6 ). Those are: a simpler method for obtaining a compound, its higher stability (as a result of replacing of labile chloro-ligands with chelate 2,2'-bipyridine) that will definitely increase its stability in the biological environment. The quantum yield of NO release from the new complex is 0.06 and is close to trans1, which is likely to be due to the trans-effect of pyridine rings in complexes. The TPA cross-sections for all three compounds cis2, trans2 and bpy2 have been investigated and are within 80-120 GM at the wavelength = 800 nm. properties. 114,115 The mechanism of the nitric oxide photorelease from ruthenium-nitrosyl compounds remains a controversial issue. And its investigation by methods of theoretical chemistry is an urgent question. However, the first step in obtaining NO from its coordination compounds is believed to be the transfer of electron density toward a strongly withdraing group {Ru-NO}. It was therefore assumed that the enhancement of the push-pull nature of the complex can increase the efficiency of this transition. Given that this electronic transcription should also be active in the TPA, further work was aimed at finding potential donor fragments that being introduced into complexes with already available acceptor group {Ru-NO} would enable the design of effective one-dimensional push-pull systems highly active in TPA. 116 In the case of long range delocalized push-pull effects, the expression of TPA can be tentatively approached by a simple two-level model involving the current g e transition as follows: 117 In the studies of Kovtunenko and Voitenko it was previously shown by theoretical calculations using several approaches and then proved with X-ray diffraction analysis and mass spectrometry that the nitrogen atom of the isoindole is strongly involved in the -delocalized structure. 120,121 Owing to an electron-rich oquinonic structure, isoindole can act as an efficient electron-donating moiety. Joining an additional pyridine ring to the isoindole core evolves 10 -electron system to 14system along with conservation of a conjugation over the entire extend of the rings. 121

Pyrido[1,2-a]indole (compound D, Figure 3.1) could theoretically also act as a donor, and the joining of the terpyridine-ruthenium-nitrosyl moiety exactly at position 6 of such a system will potentially involve all double bonds in the -system conjugation.

In the present work, various [Ru II (R-terpy)(Cl) 2 (NO)] + complexes bearing R donating substituents (isomeric to pyrido[2,1-a]isoindolyl residue) are investigated computationally in a research effort aimed at targeting suitable candidates for high values, and therefore potentially enhanced TPA response. For more thorough analysis of formally similar tricyclic systems with one nitrogen atom, we extended the spectrum of compounds and systems with those constructed from skeleton E (Fig. 3.1), varying the position of the nitrogen atom in the compound. Altogether, this approach leads to a total of 107 potential isomers.

Owing to the large number of isomers, the only ones selected here were those having the whole 14 -electrons potentially involved in the path of conjugation from the Each system is further identified by the position of the nitrogen atom, and by that of the linkage. Depending on the place of the nitrogen in the rings, and to ensure that a tertiary amine is present in any case, any -NH group is replaced by -NMe.

Finally, an ethenyl (-CH=CH-) unit is inserted between the polyaromatic system and the terpyridine moiety to reduce the steric hindrance in the molecules. This modification is achieved in order to decrease undesirable torsion angles and to enhance the conjugation of -bonds. Such alteration allows us to compare the real influence of the isomeric heterocycles on optical and electronic properties of the complexes. The compound with a fluorenyl donor substituent A' (Scheme 3.1) is a reference for comparing the nonlinear-optical properties of the studied complexes.

The ruthenium complexes were optimized in gas phase using the Gaussian-09

program package within the framework of the DFT. The details for the computed coordination spheres of the 23 complexes under investigations are provided in 2.364(2) Table 3.1. Main bond lengths (in Å) and angles (in °) in the computed coordination spheres of compounds 3.1-3.22. The values for B are experimental X-ray data, provided as references.

Quantum-chemical calculations of nonlinear optical parameters of complexes.

The relevant NLO parameters (β, β 0 , and σ TPA ) of the 22 selected isomers are gathered in Table 3.2. It is important to note that, while β corresponds to the quadratic NLO response of the entire molecule (equation 3.2), β 0 , and σ TPA refer to response of an individual transition from the (g) ground to a given (e) excited state.

The excited states given in the table correspond to the only ones providing significant β 0 values. To further simplify the understanding, β 0 , and σ TPA are expressed as relative values, those of the A' reference system being taken as 1.

The first thing to observe in the Table 3.2 is that the β values of compounds 3.1-3.22 are generally larger than that of the reference compound A'. This confirms the donating capabilities of the electron-rich heterocyclic amines. Nevertheless, this tendency is not observed in compounds 3.3, 3.9, 3.12, 3. 3.2. NLO quadratic (β and relative β 0 related to the i th transition) and cubic (relative σ TPA cross-section related to the i th transition) for 3.1-3.22, and ' for which β 0 and σ TPA are set at 1, and used as references.

emphasizes the role of the conjugation path, although the delocalization over the whole extent of the π-system is present in any case.

More generally, what strikes from the examination of Table 3.

Push-pull effects in studied complexes

Computed values around 100•10 -30 cm 5 esu -1 are rather common in conjugated organic species. 122 Values larger than 1000•10 -30 cm 5 esu -1 have occasionally been Nevertheless, comparing the differences in frequencies instead of the absolute values is more reliable in this case.

Owing to the crude tendency observed in the Figure 3.3, the values of compounds 6 and 8 should lie in the 1000 -2000•10 -30 cm 5 esu -1 range. Therefore, the large computed values (> 2500•10 -30 cm 5 esu -1 ) strongly suggest that the properties cannot be fully understood within the framework of the simplified twolevel model in these species.

The possible explanation for the observed values could be the following statement: the larger the shortest conjugation path, the higher the hyperpolarizability.

In other words, the most efficient of them are those in which the 14 π-electrons are necessarily involved in the path of delocalization. This is exemplified in Scheme 3.2 for complexes 3.10 (β = 1130 × 10 -30 cm 5 esu -1 ), and 3.11 (β = 732 × 10 -30 cm 5 esu -1 ), which contain the same R isomer, and accepting (A) moieties, but differ in the 3.3. Dominant transition for 0 : absorption maxima ( max ) in nm, intensity (f), eegg in D, and composition of the configuration interaction.

Quadratic (β β) against cubic (σ TPA ) properties of complexes.

The capability of the complexes 3.1-3.22 for TPA is estimated by the relative values ( for the reference compound A' taken as 1), calculated by formula 3.1. The experimental value is known only for the complex with the fluorenyl substituent A (Figure 3.1), which is 100 ± 13 GM. 107 The examination of the data leads to the first conclusion that, in spite of their donating capabilities, the heterocyclic amines do not enhance the σ TPA values with respect to that of the fluorenyl-based A' reference. More generally, there is no correlation between σ TPA and β 0 . Additionally, it can be observed in Table 3.2 that, when two low-lying intense transitions are present (compounds 3.2, 3.12, 3.19, 3.20, 3.22), the lowest energy transition is associated with the highest β 0 value. This is not the case for σ TPA where the highest energy transition appears to be that of larger cross-section, except in 3.12. This difference points out the versatility of the energy as a key parameter in the prediction of the NLO properties.

In push-pull species, the fact that β varies as 1/E 3 leads to the expectation of efficient NLO effects restricted to the contribution of the 1 st (HOMO/LUMO-based) excited state. In the [R-T-Ru II (Cl) 2 (NO)] + complexes built up from R-donor substituted terpyridines, the electron densities at the LUMO level are mostly located on the Ru(NO) moieties and therefore, are rather unaffected by the presence of the substituent. [START_REF] Akl | Comparative Photo-Release of Nitric Oxide from Isomers of Substituted terpyridinenitrosylruthenium(II) Complexes: Experimental and Computational Investigations[END_REF] By contrast, R provides the main contribution to the HOMO level. This is illustrated in Figure 3 that the second transition leads to higher σ TPA value. In Table 2, the only parameter which varies as σ TPA within a given molecule is the oscillator strength f, which leads to the conclusion that, in push-pull species, the two-photon absorption spectrum should be reminiscent of the one-photon absorption. Nevertheless, determining This should likely depend on the availability of the heterocyclic amine system (R)

and the possibility of its modification for further coupling with the terpyridine moiety. To reach these target species, several strategies are currently being the subject of intense investigation, notably indenopyridines (3.17 Thus in this theoretical study, for the complexes 3.1-3.22, the nonlinear optical parameters of the second order ( ) and the third order ( ) vary in wide range. The values of the TPA cross-section are generally lower than those of the reference compound A'. But the values of their hyperpolarizability in some cases are several times higher than that for A '. Nevertheless, the most promising systems correspond to the isomers of higher free Gibbs energy, thus pointing out the challenging issue of their synthetic availability.

CHAPTER 4. ENHANCEMENT OF THE EFFICIENCY OF RUTHENIUM-NITROSYL COMPLEXES IN TPA

Replacing two chloro-ligands with the 2,2'-bipyridine molecule, as shown in chapter 2, leads to a decrease in the quantum yield of nitric oxide photorelease, but somewhat increases the efficiency of the complex in two-photon absorption (TPA).

The overall efficiency of NO-donor can be estimated from its ability to release NO when the compound is activated by two photons. For this purpose it is convenient to use a parameter similar to brightness for fluorescent compounds, which is the product of the molar extinction coefficient of luminescent material ( ) and the quantum yield of the luminescence ( ). For ruthenium-nitrosyl compounds that release nitric oxide when irradiated with UV light this parameter will be the product of the molar extinction coefficient of the complex and the NO-release quantum yield ( ) -• . By replacing the molar extinction coefficient with its corresponding parameter for twophoton absorption, the TPA cross-section , we obtain the expression • , which can serve as a parameter for comparing two ruthenium-nitrosyl complexes in their ability to act as NO-donors under two-photon activation.

The strategy of the search for the optimal NO-donor should be based on an increase of both parameters, while we give preference to the enhancement of . This choice is primarily due to the fact that an increase in the quantum yield of a photorelease up to several times can significantly complicate the process of obtaining and further work with ruthenium-nitrosyl complex, since even a momentary exposition of the compound to the radiation of UV-visible frequency range of the spectrum will initiate the decomposition of the complex.

This chapter is devoted to the attempts made to increase the value of the crosssection of TPA by chemical modification of the structure of organic ligands present in ruthenium-nitrosyl complexes. In particular, there will be discussed the effect of improvement of the conjugation between the donor group and the rutheniumterpyridine fragment on the ability of the complexes to two-photon absorption, as well as the correlation between the donating ability of the substituents in the structure of the complex and their nonlinear optical property.

Influence of the efficiency of conjugation between fluorenyl and terpyridine-ruthenium nitrosyl fragments on the ability of complexes to TPA

The efficiency of the electron density transfer from a donor to an acceptor in an organic fluorenyl-terpyridine ligand of ruthenium-nitrosyl complexes depends on the angle between the terpyridine plane and the donating fragment plane. As it was noted, the overlap of orbital is stronger, the greater the cosine of the angle between them.

The compounds described in the Chapter 3 contain a double bond between the tricyclic system and terpyridine. In this way, the energy of the steric interaction of the hydrogen atoms belonging to these two parts of the ligand is reduced, which makes possible the flattenning of the ligand. A smaller angle between the mean planes of the donor and acceptor fragments makes the conjugation more efficient, and increases the ability of the molecules to display nonlinear optical properties.

We adopted this idea to obtain ruthenium-nitrosyl complexes potentially more effective in TPA. The compound bpy1 was taken as a base for them (Figure 2.2). As a donor fragment, it was decided to use a fluorenyl substituent, which showed one of the highest values of the TPA in the theoretical study comparing to heterocyclic 14electronic aromatic systems. 116 Thus, in order to find out how the diminution of the torsion angle will affect the efficacy of the compounds in TPA, we sought to obtain the compounds shown in

The synthesis of FCCT and FCC3T ligands

An attempt to obtain the ligand FCCT containing a double bond between terpyridine and fluorene through a convergent synthesis method made it possible to obtain the compound in a very low overall yield. Given the fact that the final step of synthesis occurs with a yield of about 4%, the total yield made 0.3%. The scheme of synthesis followed is shown in Scheme 4.1. was prepared according to the method described in the literature. 129 In order to improve the solubility of the ruthenium-nitrosyl complexes up to that required for the TPA (10 -2 M), we introduced two n-hexyl chains in the 9th position of the fluorenyl system, that was done at the first stage of the modification of the fluorene component. The last step of obtaining of FCCT ligand, namely the coupling reaction, occurs with a low yield, as noted above. Unfortunately, we were not able to identify the by-products of this reaction. Nevertheless, we have tried to increase the yield of the final stage of synthesis by modifying the conditions of the reaction and the catalyst.

In particular, we tried to change the position of the vinyl group. In this reaction modification, the aryl halide component of the Heck reaction was terpyridine triflate, while the vinyl moiety was attached to the fluorene. This alternative approach is shown in scheme 4.2. This method is based on the introduction of a double bond, already functionalized, through the Heck reaction between the alkylated bromofluorene 4.6

and ethyl acrylate. The further possibility of a direct transformation of the ester group into the terpyridine core eliminates the necessity for another coupling reaction. The cross-coupling stage was carried out according to an optimized technique described 96 in the literature for similar compounds. 130 The reduction of the ester 4.9 followed by the oxidation of the resulting allyl alcohol leads to the formation of the aldehyde 4.11. As the reference for this step we took the procedure of the reduction of substituted acylates, well-described in the literature. 131 Then following the typical method of obtaining of terpyridines based on the Claisen condensation of corresponding aldehyde we received a chalcone 4.12. A further Michael reaction between the compound 4.12 and the Kröhnke salt followed by heterocyclicization allowed obtaining of FCCT with the total yield of 11%. The mechanism of the reaction is given in scheme 4.4. The ligand containing the triple bond between the donor and acceptor fragments of the complex was synthesized according to a convergent scheme in 7 steps (Scheme 4.6).

The reaction of terpyridone 4.2 with triflate anhydride proceeds to give a good yield of terpyridine triflate 4.7, which was confirmed by the appearance of the signal at -72.9 ppm in the [START_REF] Fukumura | The Role of Nitric Oxide in Tumour Progression[END_REF] F-NMR spectrum. ( 1 H, [START_REF] Lepoivres | Quenching of the Tyrosyl Free Radical of Ribonucleotide Reductase by[END_REF] C) and elemental analysis.

Synthesis of ruthenium-nitrosyl complexes with FCCT and FCC3T ligands

The first step of the synthesis of ruthenium-nitrosyl complexes with terpyridine ligands FCCT and FCC3T is the interaction of the latter with ruthenium (III) chloride (Scheme 4.7).

Scheme 4.7. The general scheme of the synthesis of ruthenium-nitrosyl complexes with terpyridine ligands FCCT and FCC3T and 2,2'-bipyridine. The chemical shift of the proton highlighted in blue is the most senstitive to the substitution of monodentate ligand. The method of synthesis chosen differs from that used to obtain cis1 and trans1 compounds, in which the ruthenium-nitrosyl moiety is introduced into the structure of the complex in one step by the interaction of K 2 [RuCl 5 (NO)] with a ligand. [START_REF] Akl | Comparative Photo-Release of Nitric Oxide from Isomers of Substituted terpyridinenitrosylruthenium(II) Complexes: Experimental and Computational Investigations[END_REF] The main advantage of a new approach is the reduced formation of undesirable homoleptic complexes [Ru(tpy) 2 ] 2+ .

Thus the first stage of complex synthesis is the interaction of FCCT or FCC3T compounds with RuCl 3 , which results in the formation of a paramagnetic complex A (Scheme 4.7). In the second step, A interacts with 2,2'-bipyridine in the presence of triethylamine to form a diamagnetic complex B. Use of triethylamine facilitates the reduction of Ru III to Ru II . A possible mechanism of this process is presented in Scheme 4.8.

Scheme 4.8. The possible mechanism of Ru III reduction

The assumption of the mechanism is based on previously proposed mechanisms for the reduction of transition metal complexes with amines. 133,134 These mechanisms involve the coordination of amines to metal atoms, with the subsequent inclusion of the latter in the adjacent C-H bond, which is accompanied by its breakage. The process ends up with the reduction of the metal center and the dissociation with the proton elimination. A similar mechanism of the first stage of the process was published for a series of transition metal complexes (Pd, Rh, Fe, Ru, Au). 134,135,136 However, in the case of complexes assuming the octahedral geometry ([Fe(CN) 6 ] 3-, [Ru(bpy) 3 ] 3+ ) that apparently are not capable of coordinating an additional triethylamine molecule through an associative mechanism, the process of electron transfer from triethylamine molecule is likely to occur without direct bidning (step 1, scheme 4.8). Complex B is more likely to be attributed to this case.

An iminium cation formed as a result of the oxidation of triethylamine undergoes hydrolysis to carbinolamine (step 2, scheme 4.8) that breaks down to form diethylamine and acetaldehyde (step 3).

The use of lithium chloride in the second step of the synthesis prevents the formation of a significant amount of homoleptic complex due to the decreasing of the dissociation of chloro-ligands in the complex B.

The formation of complexes C and D can be easily monitored by NMR spectroscopy. The proton H(1) in position 6 of bipyridine (depicted in blue in scheme 4.7) is spatially approached to a single monodentate ligand present in the complex. Its chemical shift in the 1 H-NMR spectra strongly depends on the nature of this ligand (Cl, NO 2 , NO). In fact, according to the crystallographic data for the analogous complex that will be described in Chapter 5 containing substituted terpyridine and 2,2'-bipyridine ligands ([Ru II (MeO-Phtpy)(bpy)(NO)](PF 6 ) 3 ), the distance between proton H(1) and atoms of nitrosyl ligand N(1) and O(1) in the complex D are 2.595(1) and 2.719(1) Å respectively. Therefore the replacement of the ligand Cl with and finally with NO + leads to a gradual move of the peak of atom H (1) upfield. This effect is shown in Figure 4.2 for the FCC3T-based complex. When in addition to the terpyridine ligand and 2,2'-bipyridine the coordination polyhedron contains the Cl-atom, the chemical shift of the proton H(1) is 10.23 ppm (in CD3OD), whereas for its nitroanalogue the peak of the proton H(1) is at 9.90 ppm (in CD3OD). In the final ruthenium-nitrosyl complex the peak of the corresponding proton is located at 9.31 ppm (in CD3CN).

Electronic spectra of [Ru(FCCT)(bpy)NO](PF 6 ) 3 and [Ru(FCC3T)(bpy)NO](PF 6 ) 3 .

Experimental electronic spectra of both complexes and spectra obtained from quantum-chemical computations are presented in To facilitate the process of optimization of the geometries of molecular ions the quantum-chemical calculations were carried out on complexes containing methyl groups in the 9 th position of the fluorenyl moiety instead of n-hexyls. This however doesn't affect significantly the distribution of electron density in the ion.

The most obvious difference of spectrum of the complex with FCC3T ligand from the one of the complex with FCCT ligand is the presence of two absorption bands in the region 350-500 nm, while the electronic spectrum of the compound The analysis of orbitals involved in the electronic transitions in the cation Taking into account the results of the theoretical study, we assumed that the release of nitric oxide under irradiation of the complex with triple bond would be much more effective than in the case of the complex with the ligand FCCT.

The study of NO-release from complexes [Ru(FCCT)(bpy)NO](PF 6 ) 3 and [Ru(FCC3T)(bpy)NO](PF 6 ) 3

The investigation of the process of nitric oxide photorelease from complexes was carried out on their solutions in acetonitrile. The excitation occurred at a wavelength = 436 nm. This wavelength corresponds to the transition 0 7 in the compound with double bond and lies between transitions 0 1 and 0 6 in the compound with triple bond. Thus both exciations provide very different charge Interestingly, the quantum yield of the photoreaction of the nitric oxide release for both compounds was the same -0.03. This contradicts the assumption that a compound in which the excitation results in the transfer of electron density from the fluorene to ruthenium nitrosyl fragment -[Ru(FCC3T)(bpy)(NO)](PF 6 ) 3 -should display an enhanced value of NO-release quantum yield. Obviously, the transition of the electron density from the donating moiety of the complex to the antibonding orbital located on the fragment {RuNO} is not the only factor that influences the efficiency of the photoactivation of NO-release.

It should be noted that, as in the case of bpy1, the absence of a wide absorption band in the spectra of photoproducts in the region of 500-700 nm may indicate the formation of the complex with ruthenium in oxidation state +2 -[Ru(FCCT)(bpy)(CH 3 CN)] 2+ and [Ru(FCC3T)(bpy)(CH 3 CN)] 2+ .

4.1.5

The The obtained values of the two-photon absorption coefficients and the corresponding values of the TPA cross-sections are summarized in Table 4 Thus, the introduction of a multiple bond between the donor group and the acceptor terpyridine ruthenium-nitrosyl fragment in the organic ligand reduces the steric interaction between two moieties and increases the polarizability of the compound. This leads to a more efficient interaction of the -systems of both parts of the ligand and facilitates the process of intramolecular charge transfer. This effect manifests itself in the bathochromic shift of low-energy electronic transitions in the compounds and the increase of their efficiency in two-photon absorption. The compound [Ru(FCCT)(bpy)(NO)](PF 6 ) 3 exhibits a slightly lower capacity for twophoton absorption at wavelength = 800 nm compared to the [Ru(FCC3T)(bpy)(NO)](PF 6 ) 3 complex. The introduction of the triple bond leads to an increase in the TPA cross-section by 40%, while the double bond causes an increase of only by 21%. An explanation for such a difference could be the configuration of the electronic transitions of both compounds, namely: none of the electronic transitions in the molecular ion [Ru(FCCT)(bpy)(NO)] 3+ by its nature is the transfer of the electronic density from fluorene to {RuNO}-moiety, thus there is no possibility of an intense transition with a significant change in the dipole moment of the molecule.

Influence of the donating ability of the substituents in terpyridine ligands on the efficiency of ruthenium-nitrosyl complexes in TPA.

The capacity of compounds for TPA depends on many factors. One of the key parameters of a molecule which determines its ability to absorb two photons of a given energy is the symmetry of a molecule. In particular, it is known that the selection rules for transitions in centrosymmetric molecules differ from those for noncentrosymmetric molecules, and the spectra of two-photon and single-photon absorption are often very different. 104 Ruthenium-nitrosyl complexes studied within the scope of the work refer to noncentrosymmetric dipolar compounds. As indicated in Chapter 3, an approximate two-level model can be used to estimate the TPA crosssection of polar molecules, in which the excitation results in an intense transfer of electronic density. According to this model, can be described by formula 3.1 (see chapter 3):

Enhancement of conjugation in the chain of -bonds between a donor and an acceptor in a molecule results in a decrease of the energy gap between HOMO and LUMO, which reduces the E ge value, and increases the intensity of the transition (f).

These changes eventually lead to some growth of . Another factor that has a significant effect on the absorption cross section is the change in the dipole moment ( = eegg ) of the molecule during excitation, and depends on this parameter quadratically.

The increase in the -parameter can be achieved by increasing the polarity of the molecule. In this case, in the presence of a highly withdrawing ruthenium-nitrosyl site, the introduction of an electron-rich donating group into the structure could provide a significant increase in the dipole. Fluorene partially plays the role of such a group, but an additional increase in its donating ability will allow us to understand how the increase in the polarity and push-pull nature of the molecule will affect its capacity for TPA.

Syntheses of the ligands DMAFT, DMAFCCT and ruthenium-nitrosyl complexes based on them.

At the first attempt the DMAFT ligand was obtained in 7 steps (Scheme 4.9).

Scheme 4.9. The scheme of DMAFT synthesis.

The first four of them are the modification of the fluorenyl moiety -the introduction of n-hexyl substituents to form compound 4.6, its nitration (compound 4.15), the reduction of the nitrogroup in the position 7 to the amino-function (compound 4.16), and subsequent methylation of the latter to form 7-bromo-9,9dihexyl-N, N-dimethyl-9H-fluorene-2-amine (4.17). The modification was carried out by a slightly modified approach, described in the literature. 137 The last two steps of synthesis -condensation with 2-acetylpyridine and the Michael reaction followed by heterocyclicization -were carried out similarly to the reactions used to synthesize the FCCT compound, although with somewhat lower yields. Thus, the total yield of the DMAFT compound synthesis made 2%.

An attempt to optimize the synthesis path made it possible to increase the total yield of the product to 6%. The lowest yield among all the steps of synthesis was observed for methylation of aminogroup process. Along with the formation of a desired product in the reaction mixture there was a monomethylated derivative and the starting material, while the use of larger quantities of methyl iodide did not allow the production of exclusively dimethylaminofluorenyl derivative; though all three compounds could be isolated by column chromatography and re-introduced to the reaction.

In the year 2014, another method for the obtaining of dimethylamino derivatives of aromatic compounds was published. The starting compounds for these amines according to the approach are corresponding nitro compounds (Scheme 4.10). 138,139 4.10. Obtention of aromatic tertiary amines in one step from corresponding nitro derivative. This method is not yet widely used, but allows to obtain a dimethylamino derivative in one step without the use of toxic methylating reagents, such as methyl iodide or dimethyl sulfate. The transformation occurs in one step, in the presence of Fe 2+ ions playing the role of catalyst. The methylating agent in the reaction is dimethyl sulfoxide. The mechanism of the reaction involves the primary reduction of nitrofluorene to the corresponding amine. This is the point where, according to the studies of Beller and colleagues, iron ions play the role of a catalyst, and formic acid acts as a donor of hydrogen atoms. 140 The yield of the methylation reaction in such conditions is 63%, while the approach involving the transformation of nitro compound in dimethylamine derivative in two steps through the reduction step in total makes 22%. Thus we increased the yield of the synthesis of DMAFT ligand almost three times, which eventually made 6%.

An attempt to obtain DMAFCCT by a convergent synthesis method (8 steps) similar to those shown in Schemes 4.1 and 4.2 for compound FCCT was ineffective.

The total yield was 0.2%. As in the case of the FCCT synthesis, the last stage, namely the Heck coupling between compounds 4.17 and 4.5, proceeds with a very low yield of 3%.Therefore, the DMAFCCT synthesis was carried out according to a linear scheme, which is a combination of methods for obtaining of FCCT and DMAFT. The first three steps are analogous to the first stages of the synthesis of DMAFT (Scheme 4.9), the last five steps -are similar to the conversion of compound 4.6 to the final FCCT ligand (Scheme 4.3), with the only difference that the fluorene in this case contained a dimethylaminogroup.

However, the introduction of the donor function into the fluorene structure substantially changed the passage of the step of coupling with ethyl acrylate and the subsequent transformation of the ester group. In particular, the yield of Heck reaction between ethyl acrylate and compound 4.17 was almost 4 times lower than for a similar reaction of compound 4.6, which proceeded under the same conditions (Scheme 4.12). Scheme 4.12. Comparison of the yields of coupling reaction of ethyl acrylate with 2-bromofluorene (4.6) and its dimethylamino analogue (4.17) before the optimization.

An attempt to replace the catalytic system Pd(OAc) 2 /P(o-tolyl) 3 with another palladium catalyst -[Pd(PPh 3 ) 4 ] increased the yield by only 2%. However, in the case when both catalysts were introduced into the reaction mixture the yield of compound 4.24 made 77%.

The following transformations performed to obtain the DMAFCCT compound are shown in Scheme 4.13. between the values of R f for these two components of the mixture is the same as for the compounds in the previous step. Unfortunately, we were not able to identify the structure of by-products. One of the possible unwanted reactions that occur with compound 4.25 may be an allyl rearrangement. As has been shown in the studies of Jin Qu, 141 allyl alcohols are capable of undergoing rearrangement in the presence of water, albeit at elevated temperatures. Thus heating of their aqueous solutions to 40-100 °C leads to isomerisation of allyl alcohols with yields from 56% to 99%, while water plays the role of acid catalyst. It was also found that the presence of donor groups conjugated with -bond of allylic alcohol facilitates the process of isomerisation. In view of this, we assume that the following reaction could take place in the process of isolation of an alcohol 4.25 from the reaction mixture and its exposure to the air: This step of the synthesis and the subsequent oxidation process significantly reduce the overall yield of the DMAFCCT ligand. In contrast to the oxidation reaction of compound 4.10 with MnO 2 which ends in two days, the oxidation of allyl alcohol 4. 25 does not occur at all, while long-term staying of the compound in the solution results in the formation of an even greater amount of the by-product.

Additional air passage through the solution contributes to partial oxidation with the formation of aldehyde 4.26, but rapid alcohol degradation does not allow using this approach as preparative.

In the search of an appropriate oxidant the experiments on oxidation of alcohol with pure oxygen, 2 iodoxybenzoic acid (IBX) were conducted as well. The most effective method was the oxidation of alcohol with Dess-Martin reagent. The maximum yield observed for this reaction was 79%. The following condensation and Michael reaction worked with fairly good yields.

Syntheses of coordination compounds based on DMAFT and DMAFCCT ligands were conducted similarly to the general scheme 4.7. However, the attempts to obtain ruthenium-nitrosyl complexes were not successful with any of them. At the second step of the reaction -obtaining of complex B -where it becomes possible to study the product by NMR (the complex becomes diamagnetic), we observed a decrease in the integral intensity of methyl protons of dimethylamino group, and the ratio between the peak intensities of protons of n-hexyl substituents and protons of the group -NMe 2 increased. In an utmost case we observed a loss of one of methyl radicals of dimethylamino group with the formation of monomethylamine derivative. A possible explanation for this phenomenon could be the probable oxidation of the -NMe 2 group with the participation of Ru III , which occurs similarly to the triethylamine oxidation process at the second step of the synthesis of the complex This process is unexpected for us, since unlike in triethylamine the lone pair of electrons of the nitrogen atom of the amino group in the DMAFT ligand is strongly conjugated with the -system of the complex, which is evidenced by the flat structure of the ligand obtained during the DFT-optimization of the ion geometry. Therefore, the reducing properties of the -NMe 2 -group in the complex are probably weaker. As a result, the reaction mixture contained several compounds that are, unfortunately, difficult to separate. Nevertheless, obtaining of the complexes with these ligands may be possible with the modification of the approach used in this work.

Dependence of the TPA cross-section on the donor strength of the substituent in a row of ruthenium-nitrosyl complexes with substituted phenylterpyridines

Proceeding from the complexity of the process of obtaining of substituted fluorenyl-terpyridines, we have synthesized a series of ruthenium-nitrosyl complexes containing phenylterpyridines as ligands. In these compounds, the position 4 of benzene ring is substituted with groups of different electron-donating abilities: -NO 2 , -H, -Br, -OMe, -NEt 2 . The coordination polyhedra of the complexes is supplemented with two chloro-ligands, and thus the synthesized compounds are analogs of the compounds cis1 and trans1. The first stage of their preparation, as in the case of other complexes described in this work, is the interaction of ruthenium(III) chloride with the corresponding phenylperpyridine; the second step involves passing of gaseous NO through the solution of the complex in DMF that leads to the formation of cisand trans-isomers of the complex [Ru(RPh-tpy)Cl 2 NO] + . The process of nitric oxide photorelease from the obtained compounds was also investigated. The data are presented in Table 4 A detailed discussion on the ability of these complexes to release nitric oxide and the dependence of their quantum yields on the structure is given in the corresponding publication. 102 An exception is the compounds with the group -NEt 2 :

the data on these two isomers are not published at the time of the defense of the thesis, the values were obtained by M. Tasse, P. G. Lacroix and I. Malfant.

The study of the efficiency of these compounds in two-photon absorption by zscan method was carried out on their acetonitrile solutions at a concentration of indicates that there is a thermal effect that reduces the sensitivity of the measurement.

However, even when it was possible to obtain a curve without displaying a thermal effect, the signal corresponding to the minimum transmittance in the focus of the laser radiation source was commensurable to the background oscillations, which made it impossible to determine the TPA cross-sections for these compounds. All values fall in the same range of about 110-150 GM. In general, compounds with methoxyl substituent appear to be more efficient in TPA, in contrast to our expectation that the introduction of dimethylamino-function will increase the difference in the dipole moments between the main and the excited state more strongly and thus will lead to higher values of . Therefore more detailed theoretical studies of compounds are required to deeply understand the key factors that play a role in the two-photon absorption of ruthenium nitrosyl complexes with electrondonating substituents.

Thus, we have synthesized new ruthenium-nitrosyl complexes [Ru(FCCT)(bpy)NO](PF 6 ) 3 and [Ru(FCC3T)(bpy)NO](PF 6 ) 3 , where the torsion angle between fluorenyl and terpyridine fragments is reduced in comparison with bpy1.

This effect along with the elongation of the -system enhances the interaction between fragments and the polarizability of the compound. A more effective transfer of electronic density in a complex with a FCC3T ligand does not lead to a higher value of the quantum yield of NO-release, but it probably contributes to an increase in the TPA cross-section by 40% compared with bpy1, whereas for the compound [Ru(FCCT)(bpy)NO](PF 6 ) 3 this value is higher by only 21%.

It was shown that the acceptor groups in the terpyridine ligand do not lead to the increase in the value of for ruthenium-nitrosyl complexes, in contrast to the electron donating substituents.

From the point of view of the ability of the compounds to release nitric oxide upon the two-photon activation, compounds with chloro-ligands are more effective comparing to their analogs with 2,2'-bipyridine. This conclusion can be made based on the values of the product of the quantum yield of NO-release and the TPA cross-section (Table 4 The nitric oxide release from terpyridine ruthenium-nitrosyl complexes is not a one-stage process, it is quite complex to be descibed in a simplified model of electronic density transfer from a donor to an acceptor. As shown in Section 4, the introduction of donor groups leads to an increase in the TPA efficiency of the compound. However, an obvious correlation between the donor ability of the substituent and the quantum yield of nitric oxide release was not observed. This chapter is devoted to the study of some aspects of the release of nitrogen monoxidethe dependence of NO-release on the energy of exciting radiation, the structure of the photoproduct and the transformation of the released nitric oxide in vitro.

Taking into account that the highest value of the TPA cross-section was observed for the compound with the terpyridine ligand containing donating 4methoxyphenyl substituent, this ligand was selected for the synthesis of the complex with 2,2'-bipyridine and the study of the nitric oxide photorelease was conducted on this complex.

Synthesis and characterisation of the complex [Ru II (MeO-Phtpy)(bpy)(NO)](PF 6 ) 3

The ligand 4 '-(4-methoxyphenyl)-2,2':6', 2''-terpyridine (MeO-Phtpy) was synthesized according to the method described previously 142 , which involves carrying out the aldol condensation followed by the Michael addition. Following the procedure, 2 equivalents of 2-acetylpyridine are introduced in the reaction with 4methoxybenzaldehyde in a water-ethanol solution in the presence of KOH followed by addition of ammonium acetate. Equation of reaction and its mechanism are shown in scheme 5.1.

particular homonuclear COSY and heteronuclear HMQC and HMBC, allowed to confirm the structure of the resulting complex and correlate signals in NMR spectra of 1 H and 13 C (Figure 5.1).

The frequency of the valence vibrations of the N-O bond is 1940 cm -1 . The value is very close to the frequency (NO) in the bpy1 complex -1942 cm -1 -in which 2,2'-bipyridine and terpyridine ligand substituted with a donating fluorenyl substituent play the role of ligands. 107 However, it is much larger than the frequency of the valence vibrations of this bond in complexes, where the coordination sphere of ruthenium contain two chloro-ligands instead of bidentate 2,2'-bipyridine [START_REF] Akl | Comparative Photo-Release of Nitric Oxide from Isomers of Substituted terpyridinenitrosylruthenium(II) Complexes: Experimental and Computational Investigations[END_REF]102 . The difference between these values of 40-50 cm -1 is likely to arise as a result of thebackdonating interaction between 2,2'-bipyridine and the ruthenium atom and the decrease in the population of the antibonding orbitals of the nitrosyl ligand.

The structure of the complex was confirmed by X-ray diffraction analysis. An Other important interatomic distances and angles in the coordination sphere of the complex are presented in Table 5.1.

Nitrosyl Terpyridine Bipyridine

Ru(1) -N(1) 1.7668( 9) Ru(1) -N(4) 2.0888( 8) Ru(1) -N(2) 2.1002( 8) N(1) -O(1)

1.1313( 11) Ru(1) -N(5) 1.9880( 8) Ru(1) -N(3) 2.0881( 8) Ru(1)-N(1)-O(1) 172.94( 8) Ru(1) -N(6) 2.0840 (8) Table 5.1. The main interatomic distances (Å) and angles (°) in coordination sphere of the complex [Ru II (MeO-Phtpy)(bpy)(NO)](PF 6 ) 3 .

Electronic spectrum and basic electronic transitions in the compound [Ru II (MeO-Phtpy)(bpy)(NO)](PF 6 ) 3

The UV-visible spectra of [Ru II (MeO-Phtpy)(bpy)(NO)](PF 6 ) 3 and that of the related MeO-Phtpy ligand recorded in acetonitrile are compared in figure 5.3. The ligand exhibits a single and very intense band with an absorption maximum ( max ) at 284 nm ( = 37 700 mol -1 L cm -1 ). By contrast, [Ru II (MeO-Phtpy)(bpy)(NO)](PF 6 ) 3 exhibits a more complex spectrum.

While the high energy band is present ( max = 292 nm, = 38 900 M -1 •cm -1 ) and slightly red-shifted, two additional features appear at 375 nm (band 2) and 420 nm (band 3) with intensities of 18 900 mol -1 L cm -1 and 12 400 mol -1 L cm -1 , respectively.

The differences observed between ligand and metal complex strongly suggests that the contributions of the ruthenium nitrosyl withdrawing fragment are important in the low energy bands 2 and 3. Therefore, it encourages a computational analysis of the related electronic transitions. complex is, of course, more complicated.

The comparison of the experimental and computed electron spectra of the complex is presented in the The comparison between the experimental (UV-visible) and computed (TD-DFT) data are provided in Table 5.3. Although the computed wavelengths are slightly blue-shifted, the agreement is found satisfactory, thus making the interpretation at the orbital level fully reliable. Band 1 exhibits a * character, and involves the contribution of two 0 20 and 0 23 transitions centered on the bipyridine and the terpyridine, respectively. As anticipated, both low-energy bands 2 and 3 possess a strong charge transfer character towards the Ru(NO) fragment. This is further illustrated in Figure 4, where the main orbitals of interest contributing to bands 2 and 3 are drawn, with their relative energy levels. Therefore, this transition should induce an efficient NO release process. By contrast, band 2 involves the contribution of three (0 6, 0 9, and 0 10) transitions in which the dominant charge transfer occurs towards the LUMO+1 level. Interestingly, the electronic features of the LUMO+1 are closely related to those of the LUMO, with a rotation of 90° around the Ru-NO axis, and hence with the same expected effect in term of NO release capabilities. Nevertheless, the transitions involved in band 2 also involve a charge transfer towards the orbital 147 which is strongly located on the terpyridine fragment (Figure 4). Based on the assumption that the NO release process implies a single charge transfer transition towards the nitrosyl fragment, it should readily be concluded that an irradiation will be less efficient on band 2 than on band 3.

NO-release from the complex [Ru II (MeO-Phtpy)(bpy)(NO)](PF 6 ) 3

As previously shown, the release of nitric oxide from ruthenium-nitrosyl complexes results in the formation of a photoproduct in which the ruthenium is in the oxidation state +3, and the coordination position previously occupied by the nitrosyl ligand is occupied by the molecule of the solvent molecule: [START_REF] Akl | Comparative Photo-Release of Nitric Oxide from Isomers of Substituted terpyridinenitrosylruthenium(II) Complexes: Experimental and Computational Investigations[END_REF] [Ru II (NO) + ] + solvent [Ru III (solvent)] + NO • However, as discussed in chapter 2 in the case of bpy1, the photoproduct that we observe when the photoreaction finished may be different from the expected one.

Owing to the presence of two bands in the UV-visible spectrum having absorption maxima located at 375 nm (band 2) and 420 nm (band 3), the irradiations were performed at 365 nm and 436 nm using a set of available filters, in order to determine the NO release efficiencies for bands 2 and 3, respectively. 7 hours to reach completeness. Nevertheless, both experiments leading to the same photoproduct, the two figures 5.5a and 5.5b appear nearly identical.

The quantum yield of NO release ( ) observed for [Ru II (MeO-Phtpy)(bpy)(NO)](PF 6 ) 3 is equal to 0.08 and 0.03 under light irradiation at 365 nm (band 2) and 436 nm (band 3), respectively. These values are in complete disagreement with the expectation of a more efficient NO release when the charge transfer towards the Ru(NO) fragment appears more significant. Within these experimental features, the issue of the real mechanism involved in the NO release process is naturally addressed. Clearly, an explanation based on the analysis of a single charge transfer transition appears to be an oversimplified picture of a mechanism, which seems to be more complex. As described in section 1.4.4, a recent theoretical investigation has suggested that the NO release could require more than one photon, with the contribution of an intermediate triplet state. [START_REF] García | Is Photoisomerization Required for NO Photorelease in Ruthenium Nitrosyl Complexes?[END_REF] Moreover, the investigation of the ultrafast dynamics of the photoinduced NO release in a ruthenium-nitrosyl complex with terpyridine has also provided experimental evidences for a secondary photochemical process within a few ps, although it was not possible to determine the nature of the intermediate state. 144 Additionally, it is interesting to observe that the shape of the photoproduct UVspectrum (red line in figure 5.5) corresponds to a Ru II complex, because of the lack of band at 600 nm characteristic of Ru III species (see section 2.3). A similar situation was observed in the case of bpy1 compound: replacing of the chloro-ligands in terpyridine ruthenium-nitrosyl complexes with 2,2'-bipyridine led to the disappearance of such absorption in the spectrum of photoproduct. 107 In view of the presence of distinct isosbestic points in experiments with spectrophotometric monitoring of the NO-release process (Figure 5.5, Figure 2.6c), we assume that in the case when in addition to terpyridine a molecule of 2,2'bipyridine is present in the coordination environment of ruthenium in the rutheniumnitrosyl complex the photoproduct with a ruthenium atom in oxidation +3, formed in photoreaction {Ru II (tpy)(bpy)-NO} 3+ + CH 3 CN {Ru III (tpy)(bpy)-CH 3 CN} 3+ + NO, h is instantly reduced to {Ru II (tpy)(bpy)CH 3 CN} 2+ , and this photoproduct is the final one. Thus, according to our theory the cation of the complex [Ru II (MeO-Phtpy)(bpy)(NO)](PF 6 ) 3 is converted to

[Ru II (MeO-Phtpy)(bpy)(CH 3 CN)] 2+ . Additional studies to confirm this theory have been carried out.

Oxidation state of ruthenium within the release process

The study we conducted is based on a series of spectroscopic methods for analyzing the photoproducts and the very process of release of NO-radicalelectronic spectra, NMR, ESR and X-ray structural studies 145 .

If the reduction process is indeed occurs in photoproduc , then it passes very quickly, since formation of the intermediate Ru III compound is not observed in UVvisible spectra. The absence of paramagnetic particles was confirmed by NMR spectroscopy.

In view of the fact that the back reaction is not observed under the suspension of complex irradiation, we conducted an experiment to monitor the release of nitric oxide by NMR. Deuterated acetonitrile was taken as the solvent for the In contrast to the previous experiment with the acetonitrile solution of the complex, the broadening of signals was not observed at any of the steps of photoreaction, and the spectrum of the complex after the NO-release completion is similar to the spectrum of the initial substance in relative position of the signals and their integral intensity. A singlet at 3.34 ppm, characteristic for protons of water molecules is not shifted strongly in the weak field, the main shifting is observed in first minutes of irradiation. So, after 5 minutes of the sample exposure to electromagnetic radiation, the peak of water shifts from 3.34 to 4.09 ppm, and then, its position remains almost unchanged, moving in a weak field in general by another 0.11 ppm until the end of the photoreaction.

A good correspondence of the spectra of the initial complex and the photoproduct allows us to assume that the structure of the complex has not changed significantly, and apart from replacing the nitrosyl ligand with the solvent molecule, the constitution of the molecular ion has not changed.

The structure of the cationic part of the photoproduct was confirmed by the single crystal X-ray diffraction analysis of the photoproduct. The crystal was grown from an acetonitrile solution of a photoproduct that was obtained after irradiation of [Ru II (FT)Cl 2 (NO)](PF 6 ). 146 The geometry of the nitrate anions in the structure of the complex somewhat deviate from the absolute planarity. The nitrogen atoms N(8) and N(9) are located in 0.217 Å and 0.405 Å above the average plane of the three oxygen atoms. A high disorder of anions may partially be caused by this deviation. It is important that the structure of the complex consists of only two anions, which indicates that the ruthenium atom is in the oxidation state +2.

The coordination sphere of the ruthenium atom in the complex ion [Ru II (MeO-Phtpy)(bpy)(CH 3 CN)] 2+ is similar to that in the starting complex [Ru II (MeO Phtpy)(bpy)(NO)](PF 6 ) 3 . In particular, there are slight differences in the lengths of the Ru-N py bonds. Thus, in both structures, the length of the bond between the central atom and the nitrogens atom of the central pyridine ring of terpyridine is approximately 0.1 Å shorter in comparison with the bonds of the ruthenium atom with the pyridine rings. Also, on the average, Ru-N bpy bonds are slightly longer than Ru-N tpy bonds. The terpyridine fragment is more flat than in the initial complex with a maximum deviation from the average plane in 0.059 Å for the C( 19) atom. The angle between the terpyridine and bipyridine planes is 85.91 °, and the torsion angle between the terpyridine and methoxyphenyl moieties is slightly higher than the value in the initial complex -8.50 °. This is likely to indicate a less efficient conjugation between the phenyl and pyridine rings, which by-turn is caused by the reduced withdrawing effect of the {Ru(tpy)(bpy)(CH 3 CN)} fragment compared with the highly accepting ruthenium-nitrosyl group. Some parameters of the ruthenium coordination sphere, in particular the important interatomic distances and angles, are given in Table 5.4.

Acetonitrile Terpyridine Bipyridine

Ru(1) -N(1) 2.031( 6) Ru(1) -N(4) 2.080( 6) Ru(1) -N(2) 2.071(6) Ru(1)-N(1)-(1) 175.1 (6) Ru(1) -N(5) 1.967( 6) Ru(1) -N(3) 2.039( 6) Ru(1) -N(6) 2.072(6) The fact that NO-release leads to the formation of a photoproduct in the oxidation state +2 raises the issue of the real nature of the NO-species liberated under irradiation, which might not be NO-radicals, but the alternative, and undesirable NO + -cation produced by the following reaction:

[Ru II (NO) + ] + solvent [Ru II (solvent)] + NO + .
Nevertheless, the photo-generation of NO instead of NO + can be demonstrated experimentally, by EPR spectroscopy under standard excitation at = 365 nm or 436 nm, since spin trapping combined with EPR spectroscopy is considered as one of the best methods for the direct detection of NO radicals. [START_REF] Vanin | Why Iron-Dithiocarbamates Ensure Detection of Nitric Oxide in Cells and Tissues[END_REF] Namely, we used Iron(II)-Nmethyl-D-glucamine dithiocarbamato [Fe II (MGD) 2 ] to trap NO due to its high probability of adduct formation and to the high stability of its spin adduct. The appearance of the characteristic triplet signal of NO is shown in Figure 5.9. The hyperfine splitting constant value is a N = 1.24 10 -3 cm -1 , g-factor is equal to 2.040. These values are fully consistent with the literature report for [Fe II (MGD) 2 -NO] adduct. [START_REF] Vanin | Why Iron-Dithiocarbamates Ensure Detection of Nitric Oxide in Cells and Tissues[END_REF] The weak signal obs (MeO-Phtpy)Cl 2 (NO)](PF 6 ) are given as references.

141

The initial complex shows first two reduction waves at 0.44 V and 0.27 V (Figure 5.10a). At the same time, the process corresponding to the first one is reversible (Fig. 5.10c), and, according to the literature data for similar complexes, corresponds to the process of reduction of nitrosyl ligand Ru II NO + Ru II NO•. 147,148 Naturally, after irradiation and NO release completion, this reduction wave disappears.

The second wave of reduction is likely to correspond to the Ru II NO• Ru II NO process, which is not reversible. This attribution is also consistent with the published data. 148 Additional waves observed at significantly lower potentials appear due to the processes of reduction of organic ligands that are present in the complex.

The oxidation of the initial ruthenium-nitrosyl complex occurs at a potential of 1.99 V. The corresponding potential for the photoproduct is 1.93 V. The processes that determine the appearance of these waves are associated with the oxidation of ligands, most likely terpyridine, which is more enriched with electronic density. A similar behavior was observed earlier for the compound cis-[Ru II (MeO-Phtpy)Cl 2 (NO)](PF 6 ): the oxidation was observed at a potential of 1.9 V.

The most important result of the study of electrochemical oxidation of the photoproduct solution was the value of the redox potential for Ru III /Ru II pair , which makes 1.27 V. Observation of this wave in the process of the complex oxidation confirms the fact that ruthenium is in the oxidation state +2 in the compound 149 .

The data of electrochemical study can be used to evaluate the stability of Ru II /Ru III forms in solution depending on the coordination environment of the metal center. Indeed, Ru III complexes should be more prone to reduction in the case when the coordination sphere of the central atom contains five pyridine rings, i.e. {Ru(bpy)(tpy)}, than when it contains strong -donating ligands, such as chloroligands. This conclusion comes from the fact that the greater possibility of ruthenium electron density delocalization through -backdonating interaction is possible in the case of pyridine ligands. This effect stabilizes the lower oxidation state of the metal, in other words, it increases the redox potential of the Ru III /Ru II pair. As can be seen from Table 5.5, the replacement of chloro-ligands with 2,2'-bipyridine results in an increase in the potential of Ru III /Ru II pair from 0.4 V (for the compound cis-[Ru II (MeO-Phtpy)Cl 2 (CH 3 CN)] +/0 to 1.27 V (for the compound [Ru II (MeO-Phtpy)(bpy)(NO)] +3/+2 ).

Taking into account the results of the physical-chemical studies of the complex and the resulting photoproduct, it can be concluded that the release of nitric oxide from the ruthenium-nitrosyl complex [Ru II (MeO-Phtpy)(bpy)(NO)](PF 6 ) 3 leads to the formation of a product containing ruthenium atom in the oxidation state +3, which, immediately reducing transforms into [Ru II (MeO-Phtpy)(bpy

)(CH 3 CN)] 2+ .
The nature of the reductant, however, has not been investigated. On the one hand, the presence of nitrate anions in the crystalline structure of the photoproduct may indicate that the released nitric oxide can act as a reducing agent for compounds of Ru(III). On the other hand, the oxygen present in the solution can cause oxidation of NO, so there is no undeniable evidence of the direct interaction of Ru(III) complex with nitric oxide after its photorelease.

The by-product of the reaction of NO-release from the complex [Ru II (MeO-Phtpy)(bpy)(NO)](PF 6 ) 3

An attempt to crystallize a photoproduct resulted in the formation of two types of crystals. Some of the crystals corresponded to the structure of the compound [Ru II (MeO-Phtpy)(bpy)(CH 3 CN)](NO 3 ) 2 described above. While the X-ray diffraction analysis of crystals of the second type revealed the structure of another photoproduct formed during the release of nitric oxide from the initial complex.

Unfortunately, crystals of the second type were of a quality not good enough for Xray study and obtaining a crystal of higher quality of this photoproduct failed. So at this stage only the structure of the cationic part of the complex was obtained with sufficient accuracy. Its structure is shown in Figure 5.11.

As in the case with the main photoproduct, the nitrosyl ligand in the by-product is replaced with the molecule of acetonitrile, but the main difference is that the phenyl ring of the terpyridine ligand in the case of a by-product is substituted with the nitrogroup in the third position. The formation of this compound was not detected [Ru II (MeO-Phtpy)(bpy)(NO)] 3+ releases NO under irradiation in the UV-visible domain, with a quantum yield which appears significantly reduced when the involved transition exhibits a stronger push-pull charge transfer towards NO. This behavior indicates that the real mechanism of the NO-release cannot be restricted to the effect of an individual transition. Although NO is undoubtedly generated as NO radical, the concomitant Ru III photoproduct is readily reduced to a Ru II complex of formula [Ru II (MeO-Phtpy)(bpy)(MeCN)] 2+ , probably by the action of a fraction of the nitric oxide photo-released during the irradiation process. In the presence of oxygen and water nitrogen monoxide is capable of being converted into species containing nitrogen at higher oxidation states that are capable of further interaction with the photoproduct [Ru II (MeO-Phtpy)(bpy)(CH 3 CN)] 2+ forming its nitroderivative.

EXPERIMENTAL PART

Instrumentation.

Elemental analysis was performed on Perkin Elmer 2400 series II Instrument in LCC. 1 H NMR and [START_REF] Lepoivres | Quenching of the Tyrosyl Free Radical of Ribonucleotide Reductase by[END_REF] C NMR spectra were recorded on Bruker Avance III 400 (400 High resolution mass spectra (HRMS) were recorded on GCT Premier spectrometer upon electron spray ionization (ESI).

and
The melting points were determined on Stuart melting point apparatus SMP10.

In the experiment when NO-release was studied by NMR-spectroscopy, the irradiation of complex was carried out by homemade LED device at 350-450 nm wavelength range. The study was made on the samples dissolved in CD 3 CN introduced into NMR ampoules in the following conditions: 5 min of irradiation -1 NMR -5 min of irradiation and so on until the disappearance of peaks of starting material.

Electrochemical investigations were carried out at room temperature in a homemade sealed tri-electrode cell connected to vacuum-argon line using the Autolab PGSTAT100 potentiostat. A reference electrode was a saturated calomel electrode (SCE), separated from the solution by a bridge. Counter electrode was Pt wire with approximate surface area of 1 cm 2 . Main electrode was Pt microdisk (0.5 mm diameter). Electrolyte, which was used for experiment was tetrabtylammonium hexafluorophosphate (n-Bu 4 N)[PF 6 ] (Fluka, 99%, puriss, electrochemical grade) which was used directly after degassing with argon. Complex and electrolyte concentrations were about 10 -3 M and 0.1 M, respectively. Before each experiment, the solution was degassed by Ar flow, and the main electrode was polished using a Presi P230 machine. Irradiation aimed at obtaining a photoproduct with the purpose of the study of the latter by electrochemical method was carried out using homemade LED device with a wavelength range of 350-450 nm. The irradiation continued until disappearance of a characteristic signal of 2,2'-bipyridine proton at 9.32 ppm and disappearance of NO + NO• reduction band in voltamperometric analysis.

Photochemical studies.

Kinetic studies of photolysis reactions were performed using a diode-array Hewlett Packard 8454A spectrophotometer. All experiments were performed for acetonitrile non-deoxygenated solutions (volume 2 ml) of substances with where is the intensity of the light absorbed by the precursor; is the optical density before irradiation; I 0 , the incident intensity measured at 365 or 436 nm and F the photokinetic factor depending on total optical density and given by eq. 6.2: (6.2).

The equation was fitted with the experimental data parameters and B ( B is the molar extinction coefficient measured at the end of the reaction) at two wavelengths, namely, the wavelength of irradiation irr and the wavelength of observation obs , which corresponds to the largest difference between molar extinction coefficient at the initial and final moment of the photochemical reaction.

Optimization procedures were performed by using numerical integration and a nonlinear minimization algorithm. 154 bpy1:

[A] 0 = 4.94•10 5 M, = 15729 M -1 •cm 1 , = 12579 M -1 •cm -1 , = 7969 M -1 •cm -1 , = 21422 M -1 •cm -1
[Ru(F T)(bpy)NO](PF 6 ) 3 :

[A] 0 = 4.43•10 5 M, = 19639 M -1 •cm 1 , = 17156 M -1 •cm -1 , = 14756 M -1 •cm -1 , = 20442 M -1 •cm -1
[Ru(F 3T)(bpy)NO](PF 6 ) 3 :

[A] 0 = 4.48•10 5 M, = 17411 M -1 •cm 1 , = 18973 M -1 •cm -1 , = 15106 M -1 •cm -1 , = 30437 M -1 •cm -1
[Ru(MeO-Phtpy)(bpy)(NO)](PF 6 ) 3 :

under irradiation with 365 nm wavelength:

[A] 0 = 3.64•10 5 M, = 18874 M -1 •cm 1 , = 7335 M -1 •cm -1 , = 5244 M -1 •cm -1 , = 17672 M -1 •cm -1
Under irradiation with 436 nm wavelength:

[A] 0 = 4.42•10 5 M, = 11292 M -1 •cm 1 , = 18735 M -1 •cm -1 , = 13412 M -1 •cm -1 , = 5554 M -1 •cm -1
X-Ray analysis.

The data were collected at low temperature (100(2) K) with a Bruker Apex II diffractometer equipped with a 30 W air-cooled microfocus Mo-K radiation source ( = 0.71073 A) and an Oxford Cryosystems Cryostream cooler device, and and scans were used for data collection. An empirical correction using SADABS was used. 155 The structure was solved by direct methods with SHELXT. All non-hydrogen atoms were refined anisotropically by least-squares procedures on F 2 with the aid of the program SHELXL. 156,157 All hydrogen atoms were refined isotropically at calculated positions in a riding model with their isotropic displacement parameters constrained to 1.5 times the equivalent isotropic displacement parameters of their pivot atoms for terminal sp 3 carbon atom and 1.2 times for all other carbon atoms. In

Computational studies.

All the calculations were performed using Gaussian-09 program package within the framework of Density Functional Theory (DFT). Optimization of structures of all ions was performed using the hybrid functional B3PW91, which for these systems shows the best match between the theoretical results and the experimental data. This choice is also in agreement with a previous investigation of ruthenium-nitrosyl complexes made by Mascharak 158 and I. Malfant 86 group. B3PW91 has been shown

to outperform other hybrid functionals (e.g., B3LYP) and pure functionals (e.g., PW91) for numerous ruthenium complexes, especially when backbonding ligands (such as NO) are present. The vibrational analysis performed at the same level of theory as the oprimization of geometry was made to verify that the stationary points corresponded to minima on the potential energy surfaces.

The «double-» basis 6-31G* was used for all atoms except the heavy ruthenium atom, for which the LANL2DZ basis set was applied to account for relativistic effects.

Complexes cis1', trans1' and bpy1' were optimized in a gas phase, UV/Vis electronic spectra were then computed at the CAM-B3LYP/6-31G* level, which was selected for its efficient reproduction of experimental transition energies within a maximum uncertainty of 0.3 eV.

Solvent effects were included by using the polarizable continuum model (PCM) implemented in Gaussian09 for acetonitrile ( = 35.688).

Compounds 3.1-3.22 were optimized at a gas phase. For each molecule the two possible conformers resulting from the rotation around -bond between the fused heterocyclic system and the C=C double bond of the ethenyl linkage were considered (vide infra). The most stable one was selected by comparison of their Gibbs free energies (ΔG°). UV/Vis electronic spectra were then computed at the CAM-B3LYP/6-31G* level of theory. The total hyperpolarizabilities ( ) were computed at CAM-B3PYP/6-31G** level, in which p polarization functions are used on hydrogen atoms. The ten independent tensor components were computed by the derivative procedure implemented in Gaussian-09, according to the following equation:

(6.3),
where W is the energy and E the electric field. This expression is only valid for the static field limit, which corresponds to Kleinman conditions. 159 The final value is given as the magnitude of the vector ( of the radiation should be linearly related to the decrease in the transmission of the sample, which has been confirmed for each of the complexes. To verify the validity of our measurements, the same z-scan apparatus was first utilized in the closedaperture approach to measure the nonlinear refractive index n 2 of the standard CS 2 .

The results led to n 2 values in the range 1.2•10 -15 cm 2 /W, which are in very good agreement with the values accepted for this standard reference. Then, the laser dye rhodamine 6G (R6G) was measured along with the set of samples under test in the open-aperture approach. In this case, the TPA value of R6G was (67.5) GM, which is also in very good agreement with the value accepted in the literature. 160 The nonlinear absorption coefficient of each sample was obtained after fitting the normalized transmission T(z) according to eq. 6.4: Then MeOH (3.6 mL) was added slowly to the reaction mixture until complete liberation of H 2 followed by quick addition of AcOEt (300 mL). The mixture was allowed to reach a room temperature and left at intensive stirring for 1 hour followed by filtration through celite; the filtrate was evaporated under reduced pressure.

The resulting mixture was dissolved in CHCl 3 (225 mL) and MnO 2 (9.78 g, 112.5 mmol) was added. Heterogenic mixture was stirred at room temperature until complete disappearance of starting material (TLC control, for 2-3 days). After the reaction completion the mixture was filtrated through a plug of celite and filtrate was concentrated under reduced pressure. The residues were purified by column chromatography (elution system: n-hexane -EtOAc, 99:1) on silica gel to yield 3.43 g (8.2 mmol, 70%) of yellow oil. Anhydrous PhMe (60 mL) and DIPA (8.2 mL) were after added to the reaction mixture and the resulting mixture was heated at 80 ° over 36 h (TLC control). After the reaction completion it was cooled down and evaporated under reduced pressure.

The residue was dissolved in CH 2 Cl 2 , rinsed with water, brine and dried over Na 2 SO 4 .

The solvent was evaporated at reduced pressure. The product was purified by column chromatography on silica gel in two steps: 1) elution system: pentane -CH 2 Cl 2 , 9:1;

2) elution system pentane -EtOAc, 10:1 to yield 213 mg (42%) of yellowish oil.

Synthesis of complexes.

General procedure for the synthesis of [Ru(R-tpy)Cl 3 ] ( ).

Ligand (1 mmol) and RuCl Yield -390 mg (0.23 mmol, 69%).

General procedure for the synthesis of [Ru(R-tpy)(bpy)NO 2 ]Cl ( ).

Complex [Ru(R-tpy)(bpy)Cl]Cl (B) (1 equiv) and NaNO 2 (10 equiv) were dissolved in 75% EtOH/25% H 2 O mixture(124 mL for 1 mmol). The mixture was refluxed over 3h; the flask was covered with aluminium foil to protect the complex from irradiation. After the reaction completion the flask was cooled down and the volume of solvent was reduced to 1/6 of the initial volume upon concentration. The residue was left in the fridge for 2 h. The obtained precipitate was filtrated off and rinsed with cold water, a small amount of cold EtOH and diethyl ether. The complex was dried under the vacuum to yield dark red solids. .

General procedure for the synthesis of [Ru(R-tpy)(bpy)NO](PF 6 ) 3 (D).

Complex [Ru(R-tpy)(bpy)NO 2 ]Cl ( ) (1 equiv) was dissolved in EtOH (108 mL for 1 mmol of ), and the solution was mixed with the solution of HCl (12M, 108 mL for 1 mmol of , 1300 equiv) in EtOH (216 mL for 1 mmol of ). The mixture was heated to 60 ° and left stirring over 1 h; the flask was covered by aluminium foil to protect the complex from radiation. After the reaction completion the flask was cooled down and the volume of solvent was reduced to 1/5 of the initial volume followed by addition of saturated solution of NH 4 PF 6 (15 equiv)

Procedure for the synthesis of DMAFT and DMACCT:

7-bromo-9,9-dihexyl-N,N-dimethyl-9H-fluoren-2-amine (4.17).

2-Bromo-9,9-dihexyl- 46 mmol) and DMSO (6.5 mL) were placed in the reactor intended for conducting the reactions under pressure and the mixture was thoroughly degassed by Ar bubbling.

FeCl 2 •4H 2 O (9 mg, 0.045 mmol) was then added to the reaction mixture keeping the inert atmosphere in the flask. The reactor was sealed and heated at 150 ° over 14 h.

Then the reactor was cooled down to room temperature. The water (20 ml) was then added and the misture was extracted with EtOAc, organic phases were combined, washed with brine, dried over Na 2 SO 4 and filtrated off. The solvent was evaporated under reduced pressure. The residue was purified by column chromatography (elution system: hexane -EtOAc, 40:1) to yield 0.628 g (1.37 mmol , 63%) of colorless oil. The mixture of 7-bromo-9,9-dihexyl-N,N-dimethyl-9Hfluoren-2-amine 4.17 ( mixture. The suspension was heated at 90 ° for 14 h upon vigorous stirring. After the reaction completion the flask was cooled down to room temperature, and 30 ml of water was added to the mixture, that was then extracted with EtOAc. The organic phase is then washed with brine, dried over anhydrous Na 2 SO 4 , filtrated off, and the solvent was evaporated under reduced pressure. The residue was purified by column chromatography (elution system: n-hexane -EtOAc, 20:1. Yield -814 mg (1.71 mmol, 77%) of bright yellow fluorescent powder.

(E)-3-(7-(dimethylamino)-9,9-dihexyl-9H-fluoren-2-yl)acrylaldehyde (4.26).

DIBAL-H (545 μl, 1.5 M, 0.82 mmol) was added slowly in a dropwise manner to the solution of (E)-ethyl 3-(7-(dimethylamino)-9,9-dihexyl-9H-fluoren-2-yl)acrylate 4.24 (125 mg, 0.26 mmol) in anhydrous toluene (2.8 mL) in inert atmosphere at -78 °C. The reaction mixture was vigorously stirred until complete conversion of starting material (TLC control, around 4 h). Then MeOH (80 μl) was added slowly to the reaction mixture until complete liberation of H 2 followed by quick addition of AcOEt (6 mL). The mixture was allowed to reach a room temperature and left at intensive stirring for 1.5 hour followed by filtration through celite; the filtrate was evaporated under reduced pressure.

The obtained alcohol 106 mg (the spectrum is given below) was placed under vacuum and was introduced in the next step as fast as possible. 1,1,1-Triacetoxy-1,1dihydro-1,2-benziodoxol-3(1H)-one (Dess-Martin periodinane (DMP), 114 mg, 0.27 mmol) was suspended in CH 2 Cl 2 (2 mL) and mixed with tert-butyl alcohol (26 μl, 0.27 mmol). The mixture was left stirring for 20 min, then the solution of obtained alcohol in CH 2 Cl 2 (2 mL) was added and the stirring continued for 2h in a closed system. Meanwhile (after 1 h 40 min of stirring) the suspension of DMP (73 mg, 0.17 mmol) in CH 2 Cl 2 (1.5 mL) and tert-buthanol (16 μL, 0.17 mmol) was prepared. It was stirred for 20 min and after added to the reaction mixture. The final mixture was stirred for 2 h. After the reaction finished the solvent was evaporated under reduced pressure and the residue was suspended in diethyl ether followed by rinsing with 4. It was shown that the enlargement of the conjugation and its efficiency enhancement through the decrease of the torsion angle between the donating and withdrawing fragments of the complex increases the efficiency of the compound in two-photon absorption due to an increase of the push-pull character of the compound (an increase in TPA cross-section observed is 20-40%).

5. It has been demonstrated on the series of ruthenium-nitrosyl complexes with substituted phenyl-terpiridines that electron donating substituents increase the efficiency of compounds in two-photon absorption, while withdrawing groups do not lead to such improvement. The maximum TPA cross-section value is observed for the complex with the ligand 4'-(4-methoxyphenyl)-2,2':6',2''-terpyridinetrans(Cl,Cl)-[Ru(MeOPh-tpy)Cl 2 ( NO)]PF 6 -154 GM.

6. The structure of the photoproduct formed during the release of nitric oxide from the ruthenium-nitrosyl complex containing 4'-(4-methoxyphenyl)-2,2':6',2''-terpyridine and 2,2'-bipyridine has been established. It has been proved that in contrast to complexes with chloro-ligands instead of 2,2'-bipyridine, the oxidation state of ruthenium in them is +2. It was also confirmed by means of EPR spectroscopy with the use of spin trap that NO is released in a form of radical.

7. It has been established that, contrary to previous notions, the irradiation of compounds with electromagnetic waves of the energies corresponding to the energy of electron density transfer from donor to ruthenium-nitrosyl fragment does not play a decisive role in the efficiency of the compound in the process of NO release.

Irradiation at higher energies could result in photorelase with higher quantum yields.

Résumé de these

Ce travail intitulé «Libération du monoxyde d'azote induite par deux photons à partir de complexes ruthénium-nitrosyle contenant des ligands de capacités pushpull différentes» a été consacré à l'étude des principaux facteurs qui déterminent l'efficacité des complexes ruthénium-nitrosyle (Ru(NO)) dans l'absorption à deux photons (ADP) et à l'amélioration de leur section efficace ADP par modification de la nature et de la structure de leurs ligands.

A partir de complexes précédemment obtenus dans le groupe de recherche du

I

  ABBREVIATIONS ................................................................................................. INTRODUCTION ................................................................................................... CHAPTER 1. LITRERATURE OVERVIEW ................................................... 1.1 Nitric oxide: molecular structure and general chemical characteristic. ......... 1.2 Nitric oxide biological role ............................................................................ 1.3 NO generation from organic compounds ....................................................... 1.3.1 Natural pathway of nitric oxide production ............................................ 1.3.2 Classical donors of nitric oxide based on organic compounds. .............. 1.3.3 Nitrobenzenes as examples of photoactive NO-donors ........................... 1.4 NO-donors based on coordination compounds .............................................. 1.4.1 General characteristics of nitrosyl complexes. ....................................... 1.4.2 Study of metal-nitrosyl complexes by means of IR spectroscopy ............ 1.4.3. Ruthenium-nitrosyl complexes as NO donors ........................................ 1.4.4 Mechanism of nitric oxide release from ruthenium-nitrosyl complexes: theoretical studies .............................................................................................

Figure 1 . 1 .

 11 Figure 1.1. A diagram of atomic and molecular orbitals of nitrogen and nitric oxide and schematic configuration of molecular orbitals

  Figu of el mole

2NaNO 2 +

 2 2NaI + 2H 2 SO 4 = I 2 + 4NaHSO 4 + 2NO 2NaNO 2 + 2FeSO 4 + 3H 2 SO 4 = Fe 2 (SO 4 ) 3 + 2NaHSO 4 + 2H 2 O + 2NO

Figure 1 . 3 . 1 . 3 NO generation from organic compounds 1 . 3 . 1 22 Scheme 1 . 2 .

 13131312212 Figure 1.3. Cancerous tumour reaction to nitric oxide at its different concentrations

Scheme 1 . 3 .

 13 Scheme 1.3. Classification of NO-donor by the initializing of the NO release.

Figure 1 . 4 .

 14 The main representatives of the class of organic nitrates

  after the biological role of nitric oxide had been discovered. In their structure diazoniumdiolates contain [N(O-)N=O] group. Considering the atom the group is bound to, NONOate are divided into Slinked, O-linked, N-linked, or C-linked. However, only Nitrogen-bound

Scheme 1 . 5 .

 15 Scheme 1.5. Nitric oxide release from peptide-bound PYRRO/NO by enzyme activity PSA

Figure 1 . 6 .

 16 Figure 1.6. Nitrobenzene-based NO-donors

Figure 1 . 7 .

 17 Figure 1.7. New compounds based on 2,6-dimethylnitrobenzene (a) and their electronic spectra (b).

Figure 1 . 8 . 1 . 4 NO-donors based on coordination compounds 1 . 4 . 1

 1814141 Figure 1.8. Flu-DNB is a compound capable of releasing NO by two-photon photoexcitation in wavelengths of 720-800 nm.

Scheme 1 . 8 .Figure 1 . 9 .

 1819 Scheme 1.8. Resonance forms of linear and angular geometry of metal-nitrosyl complexes

  For example, in the compound [RuCl(NO) 2 (PPh 3 ) 2 ] + (Figure 1.10) 65 , both atoms of one of the nitrosyl ligands and the metal atom lie on one straight line, while the other nitrosyl ligand is bound with an angle substantially less than 180°. As shown in Figure 1.10, the lengths of the Ru-N and N-O bonds are somewhat larger in bent conformation, indicating a weakening of these bonds compared to a linear Ru-NO fragment.

Figure 1 . 10 .

 110 Figure 1.10. Structure of cation [RuCl(NO) 2 (PPh 3 ) 2 ] + (the phenyl fragments are omitted)

Figure 1 . 12 .

 112 Figure 1.12. Frequency ranges of valence vibrations of the N-O bond depending on the type of nitric oxide coordination

K 2 [Figure 1 . 13 .

 2113 Figure 1.13. Examples of the photoactive {Ru(NO)} 6 complexes with monodentate ligands

-

  Schiff's bases, thiolates, polypyridyl and other polydentane ligands. Examples of some typical ligands of these classes are shown in Figure 1.14. Schiff's bases are the classic example of the podand ligands. In 2002 '-bis(salicylidene)ethylenediamine (H 2 salen) as a ligand (Figure 1.14). Like the porphyrin ligand, compounds of this type contain four donor atoms, two nitrogen atoms in imine group and two phenolic oxygen atoms occupying four positions in the equatorial plane of the ruthenium polyhedron (Figure 1.15).

80

 80

  In this work it was also found the dependence of the photochemical activity of complexes on the ligand donor strength (Figure1.15): with decreasing ofdonating activity moving from Cl to H 2 O in the series l - -ONO --H 2 O quantum yield decreases as follows 0.13 -0.067 -0.005 respectively,. Deep investigation of ruthenium-nitrosyl complexes with PaPy 3 H type ligands (Figure 1.14) were performed by Mascharak's group. The principal feature of the structure of these ligands is the presence of the carboxamide nitrogen atom in its structure. The idea of using such a fragment was suggested by the structure of the enzyme nitrile hydratase. 81 Two of the six donor atoms in the iron coordination polyhedron in active cite of this enzyme are carboxamide Nitrogen atoms, and its activity is regulated by the coordination of nitric oxide to the central iron atom. Formation of the complex [(PaPy 3 )Ru(NO)] 2+

Figure 1 . 14 .Figure 1

 1141 Figure 1.14. Ligands for the synthesis of ruthenium-nitrosil complexes

Figure 1 . 17 .

 117 Figure 1.17. Dyes resorufin Resf (left) and fluorescein ethyl ester FlEt (right)

Figure 1

 1 Figure 1.16. Complex structure [(PaPy 3 )Ru(NO)] 2+

Fig. 1 . 19 Figure 1 . 20 .

 119120 Fig.1.19 The process for the release of nitric oxide with the simultaneous liberation of the dye molecule from 1-FlEt

Figure 1 . 21 .

 121 Figure 1.21. The structure of homoleptic complex [Ru(FT) 2 ] 2+

Figure 1 . 22 .Fig. 1 .

 1221 Figure 1.22. Electronic absorption spectra of cisand trans-[Ru II (FT)(Cl) 2 (NO)](PF 6 )

Figure 1 . 24 .

 124 Figure 1.24. Complex cation [Ru(tpy COOH )(DAMBO)NO](PF 6 ) 3

  and co-authors shows that the process of NO-release is not one-step mechanism, but rather occurs in several steps, which include the transition between several geometric forms conjugated with different electronic states of cationic ruthenium-nitrosyl complexes. The main (stationary) forms in this process are three isomeric structures of the ruthenium-nitrosyl complexes: the ground state, GS (ground state), metastable state-1, MS1 (metastable state), and metastable state-2, MS2 (Figure 1.25). In essence, they are linkage isomers: GS -ruthenium nitrosyl complex, MS1 -ruthenium isonitrosyl complex, MS2 -complex containing bridged NO ligand [Ru( 2 -NO)]. The possibility of obtaining of all three isomers was shown for the compound [RuCl(py) 4 NO] 2+ (Figure 1.25).

Figure 1 . 25 .Figure 1 . 26 .Scheme 1 . 10

 125126110 Figure 1.25. Three main isomeric forms of [RuCl(py) 4 NO] 2+ -GS, MS1 MS2.

Scheme 1 . 11

 111 Scheme 1.11 Competition between the release of nitric oxide and isomerization in ruthenium-nitrosyl complexes.

Figure 1 . 28 .

 128 Figure 1.28. Absorption of electromagnetic irradiation by biological tissues and fluids. The area of the therapeutic window (700-1300 nm).

Fig. 1 .CHAPTER 2 .

 12 Fig. 1.29 Comparison of sample volumes in which oneand two-photon absorption take place. 103

Figure 2 . 1 .

 21 Figure 2.1. The structure of cation of cis-[Ru II (FT)Cl 2 (NO)](PF 6 ) (cis1).

Figure 2 . 2 .. 2 . 1

 2221 Figure 2.2.

Figure 2 . 3 .

 23 Figure 2.3. Electronic spectra of cis1, trans1 bpy1 solutions in CH 3 CN.

  the band B in the spectra shows that for all three compounds, the most intense transitions are mostly the HOMO-LUMO transitions, with some contribution of HOMO-LUMO + 2 excitation. HOMO concentrates mainly on the fluorenyl moiety that is a donor substituent in the complexes, while the main contribution to the LUMO makes ruthenium nitrosyl fragment in which the interaction d Ru -*(NO) has an antibonding character (Figure2.4).

Figure 2 . 4 .

 24 Figure 2.4. HOMO(136 for cis1 and trans1, 159 for bpy1) and LUMO (137 for cis1 and trans1, 160 for bpy1) visualization for cis1, trans1, bpy1.

S 1 (

 1 Figure 2.5). Formally the process boils down to the transition S 0 S 1 . For a molecular ion [RuCl(py) 4 NO] 2+ this transition corresponds, in fact, to the electron transition from the Ru(d xy ) orbital to an antibonding Ru(d )NO( *) orbital. After absorption of the photon, an ultra-fast intersystem crossing (ISC) takes place and subsequent internal conversion (IC) results in the population of a triplet 3 GS state. The presence of a massive ruthenium atom in the complex furthers the rapid ISC from the state S 1 to T n , so the fluorescence from the state S1 becomes impossible. The phosphorescence from 3 GS does not occur due to the fast "barrier-free" ISC between the 3 GS and GS states. Another transition from the 3 GS level may lead to the MS2 population which can finally result in nitrosyl-isonitrosyl isomerization or release of nitric oxide. This case was discussed in paragraph 1.4.4. In the case of ruthenium-nitrosyl complexes with a terpyridine ligand containing a fluorenyl substituent, such as cis1, trans1 or bpy1, the electron transition of a lowest energy corresponds to the transfer of electron density from a donating fluorenyl moiety to LUMO located at a strongly withdrawing ruthenium-nitrosyl group. Thus, the electron density is shifted from the potentially fluorescent fluorenyl moiety: the population of the lower-energy triplet state with an electron localized on the Ru-NO fragment occurs very rapidly and the fluorescence becomes impossible. 109 2.2 Study of the release of nitric oxide from the complex bpy1.

Figure 2 . 5 .Figure 2 . 6 . 66 n

 252666 Figure 2.5. Some electron transitions in complex [RuCl(py) 4 NO] 2+ happening when its photoactivation takes place.

Figure 2 . 7 .

 27 Figure 2.7. Experimental and DFTcomputed spectra of photoproduct [Ru III (FT)Cl 2 (CH 3 CN)] + .

Figure 2 . 8 .

 28 Figure 2.8. Orbitals that participate in low-energy transitions of compound [Ru III (FT)Cl 2 (CH 3 CN)] + computed using the functionals CAM-B3LYP (on the left) and B3LYP (on the right).

CH 3 Figure 2 . 8 .

 328 Figure 2.8. The structure of obtained complexes: ) cis2, b) trans2, c) bpy2.

Figure. 2 . 9 .Compound

 29 Figure 2.9(a, b, c).For each of the studied complexes, at least 20 scans were performed at different light-pulse energies, and, as expected, an increase in the intensity of the light beam resulted in a decrease in the transmittance (T (z)) of the studied sample in the focal plane (z = 0). In all cases, irrespective of the compound and energy of irradiation, the approximation of data was in accordance of high accuracy with the law that corresponds to the change in absorption intensity at TPA.

CHAPTER 3 .

 3 PYRIDOISOINDOLE AND ISOMERIC HETEROCYCLES AS DONATING FRAGMENTS IN {Ru-NO} COMPLEXES: THEORETICALINVESTIGATION.The fluorenyl substituent acting as a donor fragment in the studied rutheniumnitrosyl complexes cis1, trans1, bpy1 and their analogs containing alkyl substituents in the 9th position of fluorene plays the role of a source of electron density transmitted to the {Ru-NO} withdrawing group upon excitation of the compound with electromagnetic radiation of 405 nm wavelength in single-photon activation, or 800-900 nm in two-photon absorption. In addition, fluorene plays the role of an antenna for the absorption of two photons in TPA. The high efficiency of this polycyclic fragment in TPA is confirmed by numerous studies and an increasing interest in its application in the design of compounds with nonlinear optical (NLO)

3 . 1 1 .

 311 In this equation, E ge is the energy of the transition, its oscillator strength, and the dipole moments in the ground and excited states, respectively. It is interesting to point out that equation 3.1 is reminiscent of the simplified but widely used "two-level" description of the first hyperpolarizability ( in equation 3.2), which relates the property to the sum of the contribution of each of the g e i transitions as follows: 118 , 3.2 an expression in which m is the mass of the electron. In the case of species exhibiting strong push-pull charge transfer capabilities, the summation is usually restricted to the contribution of a single and low-lying HOMO LUMO based (g e) transition. Furthermore, the second term of the right part of equation (3.2) is a dimensionless coefficient accounting for dispersion by resonance effect, when the incident ( ) or frequency doubled ( ) energy of the laser is getting close to the transition energy ( ). It is therefore more relevant to use the intrinsic hyperpolarizability ( 0 ), independent of the laser frequency: 3.3. It is noteworthy that expressions (3.1) and (3.3) involve the same parameters ( , f, and ). These similarities imply that a promising strategy in the search for molecules with high TPA values should be to target molecules designed for high values for which the two-level model ( 0 ) has long been applied successfullyPyridoisoindoles and isomeric heterocycles as potentially more effective fluorene analogues In the compound trans1that was taken as the reference for this study the fluorenyl substituent A (Figure 3.1), as noted, plays the role of a donor of electron density. However, the donating properties of fluorene are quite moderate. The introduction of an electron rich center delocalized within the polycyclic structure should be a means of guaranteeing an enhancement of the donating capabilities of the substituent. For instance, the introduction of pyrrole-type nitrogen atom in the central node leads to the pyrido[2,1-a]isoindole species, in which a 14--electrons path of delocalization can provide a sizeable push-pull effect either towards position 6 or 4 (B and C respectively, Figure 3.1).

Figure. 3 . 1 .

 31 Figure. 3.1. Several polycyclic systems with donating capabilities.

Scheme 3 . 1 .

 31 Scheme 3.1. Isomeric ruthenium-nitrosyl complexes with donating tricyclic substituents 6-6-5 (3.1-3.11) and 6-5-6 (3.12-3.22)and a reference compound ' .

  2 is the magnitude of the computed values, for isomeric species containing the same acceptor (NO), conjugated path length (arylethenyl-substituted terpyridine) and closely related donors. Indeed, β ranges from 233.1 (3.12) to 2751.7 (3.8) × 10 -30 cm 5 esu -1 , β 0 from 0.21 (3.20) to 3.34 (3.8), and σ TPA from <0.01 (3.6) to 1.01 (3.3).

Figure 3 1 Figure 3 . 2 . 83 Following

 313283 Figure 3.2.

Figure 3 . 3 . 6 , 3 . 7 , 3 . 8 , 3 . 2 , 3 . 12 , 3 . 19 , 3 . 20 , and 3 . 22 , 4 . 3 . 2 .

 336373832312319320322432 Figure 3.3. values against (NO) frequencies for the series of 3.1-3.22 derivatives. 3.6 and 3.8 are excluded for the computation of the trend line.

Figure 3 . 4 . 3 . 6 .

 3436 Figure 3.4. Relative β 0 against β for 3.1-3.22 and '.

20 ,

 20 .5. The HOMO energy level appears to be the ultimate microscopic parameter to account for β, along the 3.1-3.22 series: the highest the HOMO energy, the lowest the transition energy, and hence the highest the β value. and 3.22, where two low-lying intense transitions are present, the trend is

Figure 3 . 5 .

 35 Figure 3.5. HOMO (blue) and LUMO (red) energies of compounds 3.1-3.22 against .

8 ,Figure 3 . 6 .

 836 Scheme 3.1 shows that they

Figure 4 . 1 -

 41 Figure 4.1 -[Ru(FCCT)(bpy)NO](PF 6 ) 3 and [(FCC3T)(bpy)NO](PF 6 ) 3 , wherein the organic ligands FCCT and FCC3T are the compounds (E)-4'-(2-(9,9-dihexyl-9H-fluoren-2-yl)vinyl)-2,2':6',2''-terpyridine and 4'-((9,9-dihexyl-9H-fluoren-2yl)ethynyl)-2,2'6',2''-terpyridine respectively . Besides, inserting the multiple bondbetween two fragments will not only improve the conjugation but also enlarge thesystem of the molecule. Along with the decreasing of the angle, this effect would improve the polarizability of the system and consequently its ability to TPA.

Figure 4 . 1 .Table 4 . 1 .

 4141 Figure 4.1. Compounds [Ru(FCCT)(bpy)NO](PF 6 ) 3 (bottom) and [Ru(FCC3T)(bpy)NO](PF 6 ) 3 (top).

3 Scheme 4 . 1 .

 341 Scheme 4.1. Ligand FCCT synthesis by a convergent approach.

Scheme 4 . 2 .Scheme 4 . 3 .

 4243 Scheme 4.2. An alternative way of FCCT synthesis.

Scheme 4 . 4 .Scheme 4 . 5 .

 4445 Scheme 4.4. Mechanism of Michael reaction between aldehyde 4.12 and the Kröhnke salt followed by heterocyclicization.

Scheme 4 . 6 .. 14 .

 4614 Scheme 4.6. The synthesis of FCC3T ligand.

Figure 4

 4

Figure 4 . 3 .

 43 Figure 4.3. Experimental and computed electronic spectra of compounds [Ru(FCCT)(bpy)NO](PF 6 ) 3 (left) and [Ru(FCC3T)(bpy)NO](PF 6 ) 3 (right).

Figure 4 . 2 .

 42 Figure 4.2. The changes in 1 -NMR spectra when replacing the monodentate ligand in the structure of complex. Spectra of compounds [Ru(FCC3T)(bpy)Cl]Cl and [Ru(FCC3T)(bpy)NO 2 ]Cl are obtained from the solutions in CD 3 OD, [Ru(FCC3T)(bpy)NO]Cl -from the solution in CD 3 CN.

[

  Ru(FCCT)(bpy)(NO)] 3+ shows that none of the possible excitations of a molecule results in an activation of the transfer of electron density directly from fluorenyl fragment to the {RuNO} center, and the least energetic intense transition (0 7) occurs purely within the fluorenyl-terpyridine ligand. A completely different picture is observed for the ion [Ru(FCC3T)(bpy)(NO)] 3+ . Both low-energy absorption bands ( = 465 nm, = 375 nm) appear due to the presence of transitions in which the electron density moves from fluorene to the strongly accepting ruthenium-nitrosyl fragment (Table 4.5). Although similar transitions are still present in the compound [Ru(FCCT)(bpy)(NO)](PF 6 ) 3 their intensity is very small. In particular, the transition to the second excited state ( = 559 nm) is basically a HOMO-LUMO (71%) transition and this excitation causes the electron transfer from fluorene to {Ru(bpy)NO}, however, we do not observe such an absorption neither in the theoretical computed spectrum nor in the experimental because of its low intensity (f = 0.0009). An explanation for this may be the orthogonality of the HOMO ( of fluorene-terpyridine) and the LUMO (d * of RuNO) orbitals (Figure 4.4), and therefore the impossibility of the efficient transfer of the electron from the donor to the acceptor. Another transition, which, according to calculations, involves the contribution of the electronic density transfer from fluorene to the ruthenium-nitrosyl fragment, is the transition 0 6 at = 441 nm. According to

Figure 4 . 4 .

 44 Figure 4.4. HOMO and LUMO orbitals of the cation [Ru(FCCT)(bpy)(NO)] 3+ .

  transfer character: ligand-to-ligand in [Ru(FCCT)(bpy)NO](PF 6 ) 3 and ligand to RuNO in [Ru(FCC3T)(bpy)NO](PF 6 ) 3 . The change in the electronic spectra of

Figure 4 . 5 .

 45 Figure 4.5. HOMO and LUMO orbitals of the cation [Ru(FCC3T)(bpy)(NO)] 3+ .

Figure 4 . 6 .

 46 Figure 4.6. The changes in electronic spectra of acetonitrile solutions of compounds [Ru(FCCT)(bpy)(NO)](PF 6 ) 3 (left) and [Ru(FCC3T)(bpy)(NO)](PF 6 ) 3 (right) observed under irradiation with electromagnetic waves = 436 nm.

  FCCT)(bpy)(NO)](PF 6 ) 3 and [Ru(FCC3T)(bpy)(NO)](PF 6 ) 3 Investigation of two-photon absorption of both complexes was carried out at different values of the intensity of laser radiation. The increase in the energy of laser pulses (which corresponds to an increase in the intensity of the exciting light) leads to an almost linear decrease in the transmission of radiation by a sample (Figure 4.7). This fact, as well as the absence of significant distortion of the background transmission line, suggests that other effects, other than two-photon absorption, do not occur during the experiment. The transmission curves are shown in Figure 4.7.

Figure 4 . 7 .

 47 Figure 4.7. Laser irradiation ( = 800 nm) transmission curves for compounds [Ru(FCCT)(bpy)(NO)](PF 6 ) 3 (top left) and [Ru(FCC3T)(bpy)(NO)](PF 6 ) 3 (top right). Decrease in the transmission with the increase of the laser pulses intensity (bottom right).

  Therefore, we attempted to introduce a donor substituent in the fluorenyl fragment of terpyridine ligand. The dimethylaminogroup (DMA) was chosen as such a substituent. The target ligands thus were DMAFT and DMAFCCT (Figure 4.8).

Figure 4 . 8 .

 48 Figure 4.8. Strategies for increasing of TPA cross-section through modification of the terpyridine ligand structure.

Scheme 4 . 11 .

 411 Scheme 4.11. The mechanism of methylation fo aromatic aminogroup by DMSO in the presense of formic acid (R = 7-bromo-9,9-dihexy.-9Hfluoren-2-yl).

Scheme 4 . 14 .

 414 Scheme 4.14. Isomerisation of allyl alcohol 4.25 in the presence of water.

described in paragraph 4 . 1 . 2 .

 412 Scheme 4.15. A possible demethylation of [Ru(DMAFT)(bpy)Cl]Cl during the second step of the complex synthesis.

10 - 2 M

 2 . The curves of laser radiation (800 nm) transmission by the complexes solutions are shown in Figure4.9.

Figure 4 . 9 .

 49 Figure 4.9. Laser irradiation (800 nm) transmission curves, obtained during the z-scan study of complexes with substituted phenylterpyridine ligands. (the energy of laser impulses is equal to 49 nJ).

  Complexes [Ru(MeOPh-tpy)Cl 2 NO]PF 6 and [Ru(Et 2 NPh-tpy)Cl 2 NO]PF 6 , both cis-and trans-isomers, gave typical z-scan curves shown in Figure 4.9. The study of all four complexes was carried out at different values of the intensity of the exciting radiation; and with the increase of the intensity a linear decreasing of the transmittance was observed. The values of the two-photon absorption coefficients ( ) and TPA cross-sections for compounds are shown in

  assymetric unit of the elementary cell consists of one cation [Ru II (MeO-Phtpy)(bpy)(NO)] 3+ , three anions PF 6 and a molecule of acetonitrile (Figure 5.2). No -interaction was observed between the ligands -either between 2,2'-bipyridine fragments of two adjacent complex ions, or between terpyridine ligands. There is a weak interaction between the nitrosyl ligand and the anion PF 6 (O(1) -F(14) = 2.767(10) Å, O(1) -F(8) = 2.873(7)). The terpyridine fragment is almost planar with the largest deviation from the mean plane (18 atoms) of 0.154 Å (C14 atom). The bipyridine ligand is more flat with the greatest deviation from the mean plane of 0.043 Å (C9 atom). The terpyridine and bipyridine planes are almost orthogonal with a torsion angle of 87.88 °. An important parameter of the structure is the torsion angle between

Figure 5 . 2 .

 52 Figure 5.2. The structure of the asymmetric unit of the elementary cell of the complex [Ru II (MeO-Phtpy)(bpy)(NO)](PF 6 ) 3 .

Figure 5 . 3 .Table 5 . 3 . 3 .

 53533 Figure 5.3. UV/vis spectra of the ligand MeO-Phtpy (blue) and the complex [Ru II (MeO-Phtpy)(bpy)(NO)](PF 6 ) 3 (red) in acetonitrile showing the three (1-3) bands of interest present in the ruthenium(II) complex.

Figure 5 . 4 .

 54 Figure 5.4. Orbitals involved in electronic transitions of bands 2 and 3 in UV-visible spectra of the compound [Ru II (MeO-Phtpy)(bpy)(NO)](PF 6 ) 3 .

Figure 5 . 5 .

 55 Figure 5.5. Ev Phtpy)(bpy)(NO 365nm (a) and red line: after co

[

  figure 5.6.The gradual transformation of the complex into a diamagnetic photoproduct is apparent in the figure (e.g. the singlet of methyl group protons at 4.00 ppm decreases while the corresponding signal of photoproduct at 3.95 ppm rises). In general several

Figure 5 . 7 . 1 -

 571 Figure 5.7. 1 -NMR spectra of [Ru II (MeO-Phtpy)(bpy)(NO)](PF 6 ) 3 in DMSO-d 6 (bottom) and the obtained solution of photoproduct (top).

5 . 8 .Figure 5 . 8 .

 5858 Figure 5.8. The structure of the asymmetric unit of the elementary cell of the complex [Ru II (MeO-Phtpy)(bpy)(CH 3 CN)](NO 3 ) 2 .

Figure 5 . 9 .

 59 Figure 5.9. Triplet EPR signals from NO trapped by [Fe(MGD) 2 ] for [Ru II (MeO-Phtpy)(bpy)(NO)](PF 6 ) 3 upon one photon excitation at room temperature and at > 400 nm (Hg lamp) (bottom), and control signal before irradiation (top).

Figure 5 . 10 .Figure5 4 - 5 . 5 .

 510455 Figure 5.10. Square-wav complex [Ru II (MeO-Phtp the solution before (c) and

  101 MHz respectively) or Bruker Avance 300 (300 and 75 MHz respectively) spectrometer at 298 in DMSO-d 6 , CDCl 3 ,CD 3 OD, CD 3 CN or THF-d 8 ; the internal standard is the residual peaks of deuterated solvents. The degree of carbon atom substitution was determined by NMR spectra acquired according to the DEPT-135 or JMOD methods. Two-dimensional (2D) (COSY, HMQC, HMBC) spectra were recorded on a Bruker Avance III 400 (400 MHz) spectrometer. Coupling constants (J) are reported in Hz, chemical shift (δ) in ppm. The multiplicity of signals is indicated using the following abbreviations: s = singlet, bs = broad singlet, d = doublet, t = triplet, q = quartet, quint = quintet, dd = doublet of doublets, ddd = doublet of doublets of doublets, dt = doublet of triplets, td = triplet of doublets and m = multiplet. Electronic spectra were recorded on Hewlett Packard 8454A. IR-spectra were recorded on Perkin-Elmer 1725. Electron paramagnetic resonance spectra (EPR) were recorded on Bruker ESP 500E. The following parameters and methods were used: microwave power 20 mW, amplitude of field modulation 0.1 mT, field modulation frequency 100 kHz, microwave frequency 9.782512 GHz. N-Methyl-D-glucamine dithiocarbamate was synthesized in advance and injected into the reaction with ammonium iron(II) sulfate to obtain [Fe(MGD) 2 ]. 152 The 90 μl 1 mM of [Ru(MeO-Phtpy)(bpy)(NO)](PF 6 ) 3 in acetonitrile was mixed with 10 μl of 2 mM [Fe(MGD) 2 ] (in water) and injected into a quartz capillary. The sample was irradiated in EPR spectrometer by mercury lamp 250 W Oriel (Palaiseau, France). The emission light passed through the filter Oriel WG 400 UV (Palaiseau, France, > 400 nm) and was directed with the help of optical fiber.

1 ( 6

 16 concentrations: [Ru(FT)(bpy)NO](PF 6 ) 3 (bpy1) -4.94•10 -5 M, [Ru(F T)(bpy)NO](PF 6 ) 3 -4.43•10 -5 M, [Ru(F 3T)(bpy)NO](PF 6 ) 3 -4.48•10 -5 M, [Ru(MeO-Phtpy)(bpy)(NO)](PF 6 ) 3 -3.64•10 -5 M (under irradiation with 365 nm wavelength), 4.42•10 -5 M (under irradiation with 436 nm wavelength). Optical fiber was fixed from the outside of the solution cuvettes. Absorption spectra were recorded every 10 seconds in fast scan mode. Irradiation was performed until a stable absorption value was achieved. The source of radiation was a mercury lamp, equipped with light filters, allowing to receive a monochromatic light of different wavelengths. The temperature was maintained at 25 °C throughout the experiment. Measurement of the quantum yield of NO-release reaction. Light intensities were determined before each photolysis experiment by chemical actinometry procedure. The actinometer used was potassium ferrioxalate trihydrate K 3 [Fe(C 2 O 4 ) 3 ]•3H 2 O. The determined light intensity for bpy1 is 10 -6 M•s -1 , for [Ru(F T)(bpy)NO](PF 6 ) 3 is 7.05•10 -7 M•s -1 , [Ru(F 3T)(bpy)NO](PF 6 ) 3 is 8.66•10 -7 M•s -1 , [Ru(MeO-Phtpy)(bpy)(NO)](PF 6 ) 3 is 8.2•10 -7 M• -1 (under irradiation with 365 nm wavelenght), 7.81•10 -7 M• -1 (under irradiation with 436 nm wavelength). The quantum yield ( A ) was determined by the program Sa3.3 written by D. Lavabre and V. Pimienta. 153 It allows the resolution of the differential eq. 6.

  the crystal structure counter anions were highly disordered. In [Ru(MeO-Phtpy)(bpy)(NO)](PF 6 ) 3 one hexafluorophosphate anion was disordered over two positions in 74:26 ratio; in [Ru II (MeO-Phtpy)(bpy)(MeCN)](NO 3 ) 2 two nitrate anions were disordered over three positions in 48:22:30 and 40:29:3 ratios. Each disorder was modeled successfully with the atom ellipsoids restrained by SIMU, DELU and ISOR commands.

( 6 .

 6 4), where I 0 -laser pulse energy, l eff -sample thickness (0.1 cm for all the experiments), z -sample position, z 0 -Rayleigh length (parameter of the laser beam

(E)- 3 -

 3 (9,9-dihexyl-9H-fluoren-2-yl)acrylaldehyde (4.11).The solution of DIBAL-H (30 mL, 1.5 M, 45 mmol) was dropped into the solution of (E)-ethyl 3-(9,9-dihexyl-9Hfluoren-2-yl)acrylate 4.9 (6.49 g, 15 mmol) in anhydrous toluene (150 mL) under inert atmosphere at -78 °C. The reaction mixture was stirred vigorously until the complete disappearance of the starting material (TLC control).

(

  2E,4E)-5-(9,9-dihexyl-9H-fluoren-2-yl)-1-(pyridin-2-yl)penta-2,4-dien-1-one (4.12). A solution of NaOH (1.35 mL, 1M, 1.35 mmol) in water was dropped into the solution of (E)-3-(9,9-dihexyl-9H-fluoren-2yl)acrylaldehyde 4.11 (0.35 g, 0.90 mmol) and 2-acetylpyridine (0.10 mL, 0.90 mmol) in EtOH under vigorous stirring. The reaction mixture was stirred at rt until complete conversion of starting material (TLC control) The resulting precipitate was filtered off, rinsed with water and cold EtOH and dried under vacuum. The yield of 4.12 was 0.20 g (0.52 mmol, 45%). After purification of filtrate by column chromatography (elution system: hexane -AcOEt, 9:1) the extra 0.06 g was obtained (13%). The total yield was 58%, yellow powder. (E)-4'-(2-(9,9-dihexyl-9H-fluoren-2-yl)vinyl)-2,2':6',2''-terpyridine (FCCT). 1-(2-Oxo-2-(pyridin-2-yl)ethyl)pyridin-1-ium iodide (0.32 g, 0.99 mmol) and NH 4 OAc (1.04 g, 13.5 mmol) were added to the suspension of (2E,4E)-5-(9,9-dihexyl-9H-fluoren-2-yl)-1-(pyridin-2-yl) penta-2,4-dien-1-one 4.12 (0.44 g, 0.9 mmol)in EtOH (5 mL) and the mixture was refluxed until complete conversion of starting ketone 4.12 (TLC control). After the reaction finished the mixture was cooled down and evaporated under reduced pressure. The residue was diluted with water and extracted with EtOAc. The organic extracts were dried over Na 2 SO 4 followed by filtration and solvent evaporation under educed pressure. The residue was purified by column chromatography: primarily -eluent: CH 2 Cl 2 , 100%; second time -elution system: hexane -acetone, 9:1 on alumina oxide to yield 0.19 g (0.32 mmol, 36%) of yellow oil. R f 0.48 (heptane -acetone, 4:1, alumina oxide).

4 '

 4 -((9,9-dihexyl-9H-fluoren-2-yl)ethynyl)-2,2':6',2''-terpyridine (FCC3T). The mixture of 2-ethynyl-9,9-dihexyl-9H-fluorene 4.14 (311 mg, 0.87 mmol), (2,2':6',2''-terpyridin)-4'yl trifluoromethylsulfonate 4.7 (330 mg, 0.87 mmol), [Pd(PPh 3 ) 4 ] (50 mg, 0.043 mmol) was degassed and placed into inert atmosphere.

7 -

 7 (dimethylamino)-9,9-dihexyl-9H-fluorene-2-carbaldehyde (4.18). Solution of 7-bromo-9,9-dihexyl-N,N-dimethyl-9H-fluoren-2-amine 4.17(2.487 g, 5.44 mmol) in anhydrous THF (57 mL) was placed into inert atmosphere and cooled down to -78 ° . The solution of n-BuLi (2.5 M, 4.84 mL, 12.1 mmol) was adeed to the solution dropwise and the mixture was stirred over 1 h. At this point anhydrous DMF (2.12 mL, 27.4 mmol) was added dropwise to the mixture and the stirring continued for 2 h at -78 ° . The solution was then left stirring at room temperature overnight, then quenched with 1M solution of HCl. The mixture is extracted with EtOAc, organic phases were combined, washed with brine, dried over Na 2 SO 4 and filtrated off. The solvent was evaporated under reduced pressure. The residue was purified by column chromatography (elution system: CH 2 Cl 2 -hexane, 7:1) to yield 1.39 g (3.41 mmol, 63%) of yellow-green fluorescent oil.(E)-3-(7-(dimethylamino)-9,9-dihexyl-9H-fluoren-2-yl)-1-(pyridin-2-yl)prop-2-en-1one (4.19).To the solution of 7-(dimethylamino)-9,9-dihexyl-9H-fluorene-2-carbaldehyde 4.18 (736 mg, 1.81 mmol) in EtOH (10 mL), 2-acetylpyridine (204 μ , 1.82 mmol) and then ground KOH (155 mg, 2.77 mmol) were added. The reaction was controlled by TLC. After the reaction completion (around 3 h) the mixture was diluted with water and extracted with EtOAc. Organic extracts were washed with brine and dried over Na 2 SO 4 ; the solvent was evaporated under reduced pressure. The residue was purified by column chromatography (elution system: pentane -EtOAc, 100:1, with gradual increase of the polarity of the system during the elution) to yield 517 mg (1.02 mmol, 56%) of red oil.7-([2,2':6',2''-terpyridin]-4'-yl)-9,9-dihexyl-N,N-dimethyl-9H-fluoren-2-amine (DMAFT).1-(2-Oxo-2-(pyridin-2-yl)ethyl)pyridin-1-yl iodide (180 mg, 0.55 mmol) and NH 4 OAc (638 mg, 8.28 mmol) were added to a solution of (E)-3-(7-(dimethylamino)-9,9-dihexyl-9H-fluoren-2-yl)-1-(pyridin-2-yl)prop-2-en-1-one 4.19 (247 mg, 0.49 mmol) in MeOH (5 mL). The mixture was refluxed until the complete conversion of starting ketone 4.12 (TLC control). When the reaction finished the flask was cooled down to room temperature and the solvent was evaporated. Water was then added and the mixture was extracted with EtOAc. The organic phases were then combined, washed with brine, dried over Na 2 SO 4 and filtrated off. The residue was purified by column chromatography 2 times: 1) eluent: CH 2 Cl 2 , 100%; 2) elution system: nhexane -EtOAc, 15:1. The obtained oil was crystallized upon recrystallization from hexane to yield 84 mg (0.14 mmol, 28%) of yellow powder. (E)-ethyl 3-(7-(dimethylamino)-9,9-dihexyl-9H-fluoren-2-yl)acrylate (4.24).

C 6 H

 6 13 C 6 H 13 O N Na 2 S 2 O 3 (10%) and saturated aq. solution of NaHCO 3(1:1). The organic phase was rinsed with water and back extracted with small quantity of diethyl ether. Organic layers were combined, dried over Na 2 SO 4 , and the salt was filtrated off; the solvent was evaporated under reduced pressure. The residue was purified by column chromatography (n-hexane -EtOAc, 20:1) on silica gel to yield 84 mg (1.71 mmol, 79%) of bright red oil.(2E,4E)-5-(7-(dimethylamino)-9,9-dihexyl-9H-fluoren-2-yl)-1-(pyridin-2-yl)penta-2,4-dien-1-one (4.27).2-Acetylpyridine (12 μ , 0.1 mmol) was added to the solution of (E)-3-(7-(dimethylamino)-9,9dihexyl-9H-fluoren-2-yl)acrylaldehyde 4.26 (46 mg, 0.11 mmol) in EtOH (0.5 mL). Ground KOH (9 mg, 0.16 mmol) was then added. The reaction course was controlled by TLC. After the reaction finished (around 3 h) the mixture was diluted with water and extracted with EtOAc. Organic extracts were washed with brine and dried over Na 2 SO 4 ; the solvent was evaporated under reduced pressure. The residue was purified by column chromatography (elution system: pentane -EtOAc, 100:1, with gradual increase of the polarity of the system during the elution) to yield 35 mg (0.065 mmol, 61%) of red oil. (E)-7-(2-([2,2':6',2''-terpyridin]-4'-yl)vinyl)-9,9-dihexyl-N,N-dimethyl-9H-fluoren-2amine (DMAFCCT). 1-(2-Oxo-2-(pyridin-2-yl)ethyl)pyridin-1-yl iodide (99 mg, 0.30 mmol) and NH 4 OAc (350 mg, 4.54 mmol) were added to a solution of (2E,4E)-5-(7-(dimethylamino)-9,9-dihexyl-9Hfluoren-2-yl)-1-(pyridin-2-yl)penta-2,4-dien-1one 4.27 (143 mg, 0.27 mmol) in MeOH (5 mL). The mixture was refluxed until the complete conversion of starting ketone 4.27 (TLC control). After the reaction completed the flask was cooled down to room temperature. After the solvent was

1 . 2 . 8 ) 3 .

 1283 It was shown that the introduction of 2,2'-bipyridine as a ligand into the structure of ruthenium-nitrosyl complexes instead of the two chloro-ligands leads to a decrease in the quantum yield of nitric oxide photorelease from 0.11 (trans(Cl,Cl)-[Ru II (FT)Cl 2 (NO)](PF 6 )) to 0.06, however, it leads to an increase in the TPA crosssection from 90-100 GM to 108 GM. By means of quantum-chemical calculations it has been demonstrated that the introduction of azaheterotricyclic systems with a 14 -electron conjugation system into the structure of the terpyridine ligand in the ruthenium-nitrosyl complex may contribute to a weak increase in the efficiency of the compounds in two-photon absorption (the maximum TPA cross-section obtained for the compound 1-methyl-1H -benzo[f] indole (compound 3.3) is only 1% higher than that for the reference compound trans1, the TPA cross-section for which is 87GM) However, the replacement of fluorene with such heterocyclic analogues substantially alters the ability of compounds to hyperpolarization, the value of which varies depending on the heterocycle from 233.1•10-30 cm 5 •esu -1 (compound 3.12) to 2751.7 •10-30 cm5 •esu -1 (compound 3.Preparative methods for synthess of ruthenium-nitrosyl complexes with ligands containing different types of linker between donor fluorenyl and withdrawing terpyridine fragments have been developed -[Ru(FCCT)(bpy)NO](PF 6 ) 3 , [Ru(FCC3T)(bpy)NO](PF 6 ) 3 .

  Prof. I. Malfant, nous avons effectué diverses modifications structurales. Il a été montré que la substitution des ligands monodentes par la 2,2'-bipyridine dans les complexes de Ru(NO) conduit à une légère augmentation de la section efficace, mais cette modification diminue le rendement quantique du relargage du monoxyde d'azote (NO). La partie synthétique du travail a principalement porté sur la modification du ligand 4'-(9H-fluorène-2-yl)-2,2':6',2''-terpyridine. L'extension de la conjugaison doit améliorer la polarisabilité du ligand et le caractère «push-pull» du complexe. Cela entraîne une efficacité accrue des composés en ADP qui a été confirmée expérimentalement durant ce travail. L'insertion d'une double liaison au centre du système entre les fragments donneurs et accepteurs conduit à une augmentation de 20% de la section efficace, alors que la triple liaison apporte un gain de 36% et apparaît comme un meilleur transmetteur. La différence des moments dipolaires entre les états fondamentaux et excités des molécules est un paramètre additionnel particulièrement sensible aux modifications structurales des composés. Il mérite une attention particulière car il intervient dans l'expression de l'efficacité ADP en apportant une quantification de l'effet «push-pull». Pour augmenter sa valeur, nous nous sommes fixé comme objectif la synthèse de complexes possédant des ligands porteurs du substituent donneur diméthylamino. Après optimisation de la synthèse de ces ligands, l'obtention des complexes afférents par la méthode habituelle de synthèse des complexes Ru(NO) a été un échec. En effet, la deuxième étape de la 206 synthèse conduit à une oxydation progressive du groupement diméthyamino avec déméthylation. L'étude d'une autre série de complexes plus accessibles avec des groupements donneurs de forces diverses a permis de mettre en évidence certaines tendances. Ces complexes contiennent des cycles phényles, portant des groupes fonctionnels accepteurs (nitro-) et donneurs comme métoxy-et diméthylamino-. Il a été montré que, si la présence de groupes accepteurs ou neutres a peu d'effet sur la section efficace, la présence de donneurs conduit à une amélioration des propriétés avec une valeur maximale de section efficace de 154 GM observée pour le complexe avec le ligand 4'-(4-méthoxyphényl)-2,2':6',2'' -terpyridine. L'expérience confirme l'hypothèse initiale selon laquelle l'augmentation de la différence des moments dipolaires entre les états fondamentaux et excités des molécules conduirait à une efficacité ADP accrue dans ce type de molécules. Une large part de ce travail a impliqué des calculs théoriques effectués à partie de la théorie de la fonctionnelle de la densité (DFT). En marge des effets liés à la photo-libération de NO, les propriétés optiques non linéaires des complexes de Ru(NO) ont été étudiées sur le plan théorique. L'effet de la substitution du fragment fluorényle par 22 analogues hétérocycliques différents ayant un squelette tricyclique similaire et contenant un atome d'azote donneur a été évalué afin d'améliorer la conjugaison et d'optimiser la longueur et la forme du systèmeconjugué. Il a été montré que, bien qu'une telle modification ne conduise pas à une amélioration notable, de tels composés pourraient être intéressants en tant que matériaux pour l'optique non linéaire. La structure du photoproduit et le degré d'oxydation du ruthénium sont discutés en détail. Contrairement au photoproduit précédemment étudié, les complexes possédant cinq cycles pyridine dans la sphère de coordination du métal conduisent à des complexes de Ruthénium(II) pendant le processus de photolibération de NO, alors que la formation de radical NO est confirmée par spectroscopie RPE. région spectrale visible, mais pour le composé 1c, on observe un décalage bathochrome de cette bande par rapport aux complexes contenant des ligands chloro. Dans ce cas, le coefficient d'extinction molaire de la bande B du composé 1c est légèrement inférieur.

Figure 2 .

 2 Figure 2. Spectres électroniques des solutions des complexes 1 , 1b, 1c dans CH3CN.

Figure 3 .Tableau 1 .

 31 Figure 3. Visualisation de HOMO et LUMO pour les composés 1a, 1b, 1c.

Figure 5 . 4 Figure 6 .

 546 Figure 5. Structures de résonance du substituant hétérocyclique cyclopenta[b] quinolizine dans les complexes 11 et 12, où le groupe de retrait A est situé respectivement aux positions 6 et 4

Figure 7 .Schéma 1 .Schéma 2 .Schéma 3 .Schéma 4 .Schéma 5 .

 712345 Figure 7. Les structures des complexes Ru(FCCT)(bpy)NO](PF 6 ) 3 (24a) et [Ru(FCC3T)(bpy)NO](PF 6 ) 3 (24b).

Figure 8 .

 8 Figure 8. Evolutions des spectres électroniques des composés [Ru(FCCT)(bpy)(NO)](PF 6 ) 3 (gauche) et [Ru(FCC3T)(bpy)(NO)](PF 6 ) 3 (droite) dans l'acétonitrile = 436 nm.

Figure 9 . 3 (

 93 Figure 9. Les structures du complexe initial [Ru II (MeO-Phtpy)(bpy)(NO)](PF 6 ) 3 ( ) et du photoproduit correspondant [Ru II (MeO-Phtpy)(bpy)(CH 3 CN)](NO 3 ) 2 (b).

Figure 10 .CONCLUSIONS 1 . 2 . 1 (composé 9). 3 . 4 . 5 . 6 . 7 .

 1012134567 Figure 10. Suivi RMN de la libération de NO par [Ru II (MeO-Phtpy)(bpy)(NO)](PF 6 ) 3 irradié avec une lumière continue dans la plage de 350-450 nm, dans CD 3 CN.

Table 1

 1

		.1 presents a general information about all nitrosyl complexes
	found in the Cambridge Structural Database (CSD) in 2014. 60
	Angle (°)	Number of	Geometry	Example
		structures
	180-160	2519	Linear	[Mn(NO)(CO)4] 61
	160-140	121	Intermediate	[Ir(NO)2(PPh3)2] 62
	140-100	115	Angular	[Co(NO)(S2CN(CH3)2)2]

Table 1 .

 1

1 Generalization of metal-nitrosyl complexes from the CSD database in 2014 There are complexes (absent in the table above) that contain metal atoms bound both to oxygen and nitrogen atom of the NO group. Total number of such complexes is small; usually they are unstable and could form as a result of photoexcitation of nitrosyl complexes as transitional states. The particular example of such compounds is [Ni(NO)( 5 -Cp*)], where Cp -pentamethylcyclopentadienyl anion. The Ni-N distance in it is only 0.4 Å shorter than the Ni-O distance, and the Ni-N-O angle is 93°.

Table 1 .3. The

 1 A brief summation is presented in Table 1.3. influence of ligands of different nature and charges on the vibrational frequency of nitric oxide in complexes.

	Charge and ligands	(NO) (cm -1 )
	. Ionic charges
	Unit of positive charge	+100
	Unit of negative charge	-145
	B. Electron-withdrawing ligands
	Linear cyanide	+50
	Linear halogens	+30
	Bridging halogens	<+15
	C. Linear or bridging CO ligand	0
	D. Electron-donating ligands
	PF 3	+10
	P(OPh) 3	-30
	PAlk 3 (Alk -alkyl) 5 -C 5 H 5 5 -C 5 H 4 Me 5 -C 5 Me 5	-70 -60 -70 -80

Table 2 . 2 .

 22 .2). Comparison of experimental and theoretical parameters of band B in electronic spectra of compounds A detailed analysis of the electron excitations responsible for the appearance of

	Compound Experimental data	TD-DFT computations
		max		max	f
	cis1	389	24950	355	0.724
	trans1	414	23600	370	0.665
	bpy1	440	16700	428	0.331

Table 2 . 3 .

 23 .3. TD-DFT-computed parameters of electron transitions with electron charge transfer onto {Ru-NO}. (Orbitals 136 are HOMO, orbitals 137 -LUMO for compounds cis1 and trans1; orbital 159 is HOMO, orbital 160 -LUMO for bpy1. g 0 -ground state, n -n th excited state.)

	Compound transition max f	Main excitations contributions
	cis1	g 0 e 6	355	0.724 18.96	136 137 (50.8 %) + 136 139 (19.7 %)
	trans1	g 0 e 6	370	0.665 22.77	136 137 (69.2 %) + 136 139 (10.8 %)
	bpy1	g 0 e 1	428	0.331 30.07	159 160 (80.6 %) + 159 162 (4.8 %)

Table 2 .

 2

	4
	sections

Table 3 .

 3

	In the table 3.1 the parameters of cordination sphere of 23 complexes are
	compared to that of the previously reported complex trans1. The computed
	coordination spheres appear similar in any case, with largest relative bond lengths
	difference of 0.6 % observed at the Ru-N (central pyridine) between 3.7 (1.993 Å)
	and 3.12 (2.006 Å). The agreement with the experimental data available is found
	satisfactory, with a general shortening of bond lengths in the X-ray geometries, from
	those computed by DFT.

1.

The details of computational methods used are presented in experimental part of the work (Chapter 6).

14, and 3.20, which

	Compound	β (10 -30 cm 5 esu -1 )	# excited state	relative β 0 value	relative σ value
	3.1	487.2	i=1	0.83	0.24
	3.2	732.3	i=1	0.96	0.56
			i=5	0.63	0.57
	3.3	450.4	i=1	1.32	1.01
	3.4	475.8	i=1	0.90	0.30
	3.5	502.3	i=1	1.34	0.48
	3.6	2709.9	i=1	0.58	< 0.01
	3.7	1539.5	i=1	2.82	0.57
	3.8	2751.7	i=1	3.34	0.09
	3.9	301.4	i=1	0.29	0.15
	3.10	1130.0	i=1	0.96	0.10
	3.11	733.2	i=1	1.37	0.03
	3.12	233.1	i=3	0.48	0.52
			i=5	0.15	0.21
	3.13	754.2	i=1	1.43	0.48
	3.14	376.1	i=1	0.74	0.24
	3.15	540.4	i=1	0.85	0.28
	3.16	553.3	i=1	1.04	0.53
	3.17	975.3	i=1	0.97	0.28
	3.18	855.1	i=1	1.30	0.27
	3.19	782.8	i=1	0.94	0.08
			i=8	0.19	0.10
	3.20	328.8	i=1	0.21	0.03
			i=7	0.21	0.11
	3.21	1289.8	i=1	1.48	0.34
	3.22	1041.2	i=1	1.11	0.25
			i=8	0.54	0.43
	'	463.2	i=4	1	1
	Table

Table 3 .

 3 The fact that they are associated with transitions of unusually weak intensity(3.8) or unusually reduced μ ee -μ gg value (3.6) makes these species definitely unconventional. And understanding of the nature of these compounds requires both more profound theoretical and experimental analyses that, by-turn, raises the issue of the synthetic feasibility of such complexes.

	Compound transition	λ max	f	μ ee -μ gg	composition
	3.1	0	1	581	1.14	8.22	HOMO LUMO (87 %)
	3.2	0	1	623	0.46	19.2	HOMO LUMO (83 %)
	3.3	0	1	578	0.70	21.7	HOMO LUMO (82 %)
	3.4	0	1	569	1.18	9.17	HOMO LUMO (85 %)
	3.5	0	1	662	0.76	13.5	HOMO LUMO (76 %)
	3.6	0	1	2183	0.12	1.07	HOMO LUMO (59 %)
	3.7	0	1	824	0.96	11.7	HOMO LUMO (84 %)
	3.8	0	1	2236	0.06	10.9	HOMO LUMO (85 %)
	3.9	0	1	727	0.07	22.9	HOMO LUMO (77 %)
	3.10	0	1	881	0.45	6.84	HOMO LUMO (83 %)
	3.11	0	1	896	0.32	13.3	HOMO LUMO (67 %)
	3.12	0	3	496	0.39	22.7	HOMO LUMO (80 %)
	3.13	0	1	699	0.67	13.9	HOMO LUMO (80 %)
	3.14	0	1	555	1.14	8.43	HOMO LUMO (87 %)
	3.15	0	1	709	0.38	13.9	HOMO LUMO (80 %)
	3.16	0	1	603	0.68	15.6	HOMO LUMO (80 %)
	3.17	0	1	920	0.13	20.8	HOMO LUMO (74 %)
	3.18	0	1	656	1.34	7.60	HOMO LUMO (92 %)
	3.19	0	1	919	0.41	6.50	HOMO LUMO (67 %)
	3.20	0	1	999	0.03	13.9	HOMO LUMO (78 %)
		0	7	514	0.30	11.8	HOMO-1	LUMO (73 %)
	3.21	0	1	756	0.68	11.1	HOMO LUMO (87 %)
	3.22	0	1	822	0.59	9.77	HOMO LUMO (65 %)
	'	0	4	464	1.21	18.4	HOMO LUMO (79 %)
	Table

3

. Finding λ max values in the 500 -1 000 nm range is fully acceptable in push-pull molecules with delocalization over the whole extent of a chain containing more than 20 π-electrons. Nevertheless, λ max values larger than 2 000 nm (3.6 and 3.8) are rather surprising.

Table 4 . 3

 43 PF 6 ) 3 are presented in Table 4.2 and Table 4.3, respectively.

	[Ru(FCCT)(bpy)NO](PF 6 ) 3 shows only one absorption band at these wavelength. The
	spectra calculated by the TD-DFT method are in an acceptable agreement with the
	experimental results. The largest deviation of 0.35 eV can be observed for the low-
	energy band of the complex [Ru(FCCT)(bpy)NO](PF 6 ) 3 .
	The parameters of the absorption bands in the experimental and computed
	electronic	spectra	of	the	complexes	[Ru(FCCT)(bpy)NO](PF 6 )	and
	[Ru(FCC3T)(bpy)NO](Experimental spectrum		Computed spectrum
		max (nm)		(M -1 • m -1 )	max (nm)	f
	Band 1	308		36 215		291	0.8189
	Band 2	493		25 103		432	1.6337
	Table 4.2. Absorption bands in experimental electronic spectrum of the compound
	[Ru(FCCT)(bpy)NO](PF 6 ) 3 compared to those of electronic spectrum for the ion [Ru(FCCT)(bpy)NO] 3+ computed by TD-DFT at CAM-B3LYP/6-31G* level of
	theory.
		Experimental spectrum		Computed spectrum
		max (nm)		(M -1 • m -1 )	max (nm)	f
	Band 1	296		47 386		279	0.8010
	Band 2	375		18 729		381	0.8425
	Band 3	465		20 200		457	0.8027

. Absorption bands in experimental electronic spectrum of the compound [Ru(FCC3T)(bpy)NO](PF 6 ) 3 compared to those of electronic spectrum for the ion [Ru(FCC3T)(bpy)NO] 3+ computed by TD-DFT at CAM-B3LYP/6-31G* level of theory.

Table 4 .

 4

	4. TD-DFT computed absorption maxima, oscillator strengths and configurations of electronic transitions of the	cation[Ru(FCCT)(bpy)(NO)] 3+ . Orbital 174 is HOMO, orbital 175 -LUMO.

Table 4

 4

.4, this excitation doesn't imply the charge transfer from fluorene to ruthenium-nitrosyl moiety, but as little as 4% of contribution to 0 6 is still made by the excitation 174 176 , where 174 -HOMO,

Table 4 .

 4

	.6.

Table 4

 4

			.8.
		[Ru(MeOPh-tpy)Cl 2 NO]PF 6	[Ru(Et 2 NPh-tpy)Cl 2 NO]PF 6
		cis-	trans-	cis-	trans-
	•10 11 cm/W	3.22	3.73	3.44	2.73
	, GM	133	154	142	113

Table 4 . 8

 48

. TPA coefficients and cross-sections for cis-and trans-isomers of compounds [Ru(MeOPh-tpy)Cl 2 NO]PF 6 and [Ru(Et 2 NPh-tpy)Cl 2 NO]PF 6 .

Table 4 .

 4 .9).The main effect on the product (NO)• is made by the quantum yield of NOrelease, since these values vary considerably more broadly -the maximum value (0.31) is 10 times larger than the smallest (0.03), whereas the difference between the largest value of (154 GM) and the smallest (87 GM) one is only 77%.

	(NO)	, GM	(NO)•

9.

The values of quantum yields, TPA cross-sections and the products of these two parameters for ruthenium-nitrosyl complexes, studied within the scope of this thesis. 123 CHAPTER 5.

INVESTIGATION OF THE MECHANISM OF NO- PHOTORELEASE FROM RUTHENIUM-NITROSYL COMPLEX WITH THE LIGAND 4'-(4-METOXYPHENYL)-2,2':6',2''-TERPYRIDIN

table 5

 5 Absorption bands in the electronic spectrum of the complex [Ru II (MeO-Phtpy)(bpy)(NO)](PF 6 ) 3 , and corresponding absorption bands for the ion [Ru II (MeO-Phtpy)(bpy)(NO)] 3+ , computed by means of TD-DFT on the CAM-B3LYP/6-31G* level of theory.

			.2.
		Experimental spectra	Computed spectra
		max (nm)	(M -1 • -1)	max (nm)	f
	Band 1	292	38 900	265	0.628
	Band 2	375	18 900	342	0.632
	Band 3	420	12 400	417	0.227
	5.2.

Table 5 .

 5

4. Main bond lengths (Å) and angles (°) in the coordination sphere of ruthenium in [Ru II (MeO-Phtpy)(bpy)(MeCN)] 2+ .

procedures for the syntheses of ligands and their precursors.

  ). Rayleigh length was established by the «knife-edge method», and was 0.190 cm when studying cis2, trans2 and bpy2; 0.066 cm when studying cis(Cl,Cl)-[Ru(MeOPhtpy)Cl 2 NO]PF 6 , trans(Cl,Cl)-[Ru(MeOPh-tpy)Cl 2 NO]PF 6 , cis(Cl,Cl)-[Ru(Et 2 NPhtpy)Cl 2 NO]PF 6 , trans(Cl,Cl)-[Ru(Et 2 NPh-tpy)Cl 2 NO]PF 6 ; 0.101 cm when studying PPh 3 (138 mg, 0.53 mmol) and Et 3 N (0.98 mL, 7.00 mmol) in inert atmosphere. The resulting suspension was heated at 90 ° under vigorous stirring over 14 h. After the completion of the reaction was cooled down to rt followed by H 2 O (70 mL) adding. The mixture was extracted with EtOAc; the organic extracts were washed with brine, dried over Na 2 SO 4 and filtrated. The solvent was evaporated

	[Ru(FCCT)(bpy)NO](PF 6 ) 3 and [Ru(FCC3T)(bpy)NO](PF 6 ) 3 . The values of absorption cross-sections were calculated according to formula 6.5: 2-bromo-9,9-dihexyl-9H-fluorene (4.6). 2-Bromofluorene (11.65 g, 0.048 mol) and (0.79 g, 4.76 mmol) were dissolved in DMSO (96 mL) upon slight heating. After complete dissolving the mixture was degassed and put under inert atmosphere. KOH (9.16 g, 0.164 mol) was then pestled and added to the solution under Ar flow. The mixture was stirred for 20 min followed by n-0.21 mmol), under reduced pressure and the residues were purified by column chromatography
	(6.5), bromohexane (17 mL, 0.121 mol) dropping into the reaction mixture in 5 portions, (elution system: n-hexane -EtOAc, 200:1) on silica gel to yield 2.48 g (5.73 mmol,
	very slowly, with intensive stirring. The interval between portions was 10 min. After 82%) of yellow oil.
	the addition was completed, the mixture was left stirring at room temperature for 3
	where N -concentration of the molecule (molecule/l), hours followed by water addition and extraction with EtOAc. The organic layer was -frequency of laser
	radiation. washed with brine and dried over Na 2 SO 4 . The product was purified by column
	chromatography (eluent: pentane, 100%) to yield 19.63 g (99.9%) of colorless oil.
	The Compounds 4.1 126 , 4.2 126 , 4.5 129 , 4.7 161 , 1-(2-oxo-2-(pyridin-2-yl)ethyl)pyridin-1-ium 9,9-dihexyl-2-vinyl-9H-fluorene (4.8).
	iodide 132 , 4.15 137 , 4.16 162 , 4.17 137 , 4'-(4-methoxyphenyl)-2,2':6',2''-terpyridine 142 were 2-Bromo-9,9-dihexyl-9H-fluorene (960 mg, 2.32 mmol),
	synthesized according to the reported procedures. KBF 3 C 2 H 3 (334 mg, 2.49 mmol), Pd(OAc) 2 (70 mg, 0.31
	mmol), PPh 3 (233 mg, 0.89 mmol) and Cs 2 CO 3 (1936 mg,
	The synthesis of FCCT and FCC3T ligands: 5.94 mmol) were suspended in THF (30 mL) and 2 (1.5 mL) mixture and placed
	4'-bromo-2,2':6',2''-terpyridine (4.3). into teflon reactor. The mixture was degassed under the intense Ar flow and sealed.
	PBr 5 (8.09 g, 19 mmol) was added to the suspension of The mixture was heated at 100 °C under the vigorous stirring over 48 h. The resulting
	(2,2':6',2''-terpyridin)-4'(1'H)-one 4.2 (1.93 g, 7.75 mmol) in mixture was diluted with H 2 O and extracted with CH 2 Cl 2 . Organic extracts were
	DMF (50 mL) and heated at 90-93 ° for 20 h. The reaction washed with brine, dried over Na 2 SO 4 and filtrated. The solvent was evaporated
	mixture was then cooled down and 80-100 mL of water were under reduced pressure and the residues were purified by column chromatography
	carefully added followed by neutralization with Na 2 CO 3 . The mixture was extracted (eluent: hexane, 100%) on silica gel to yield 227 g (0.63 mmol, 27%) of colorless oil.
	with CH 2 Cl 2 . The organic phase was washed with brine, dried over Na 2 SO 4 and
	filtrated. The solvent was evaporated under reduced pressure and the residues were (E)-ethyl 3-(9,9-dihexyl-9H-fluoren-2-yl)acrylate (4.9).
	purified by column chromatography (elution system: CH 2 Cl 2 -hexane, 2:1) on Ethylacrylate (1.12 mL, 10.50 mmol) and anhydrous DMF
	alumina yielding 1.69 g (5.42 mmol, 70%) of light beige solid. (7 mL) was added to the mixture of 2-bromo-9,9-dihexyl-
	9H-fluorene 4.6 (2.89 g, 7.00 mmol), Pd(OAc) 2 (47 mg,

  After 3h the flask was cooled down and the volume of solvent was reduced to 1/3 of the initial volume upon evaporation under reduced pressure. The residue was left in the fridge for 2 h. The obtained precipitate was filtrated off and was thoroughly rinsed with cold water (until the colorless drops of filtrate), chilled EtOH and diethyl ether. The complex was dried under vacuum to yield brown-black solids. .

	[Ru(MeO-Phtpy)Cl 3 ]: [Ru(FCC3T)(bpy)Cl]Cl:
		N	Cl		Starting materials: 4'-(4-methoxyphenyl)-2,2':6',2''-Starting materials: [Ru(FCC3T)Cl 3 ]
	O	N	Ru	Cl	terpyridine MeO-Phtpy (250 mg, 0.74 mmol), (169 mg, 0.21 mmol), 2,2'-
		N	Cl		RuCl 3 •xH 2 O (Ru: 40-49%; 192 mg). EtOH (48 mL) bipyridine (33 mg, 0.21 mmol),
	Yield -335 mg (0.61 mmol, 83 %).	LiCl (64 mg, 1.5 mmol), Et 3 N (60
	3 •xH 2 O (Ru: 40-49%; 251 mg for μL, 0.42 mmol), 75% EtOH/25% H 2 O (25 mL). Yield -162 mg (0.23 mmol, 83%).
	1 mmol of ligand, 1-1.22 equiv) were suspended in ethanol General procedure for the synthesis of [Ru(R-tpy)(bpy)Cl]Cl ( ).
	(65 mL for 1 mmol of ligand). The mixture was refluxed Complex [Ru(R-tpy)Cl 3 ] ( ) (1 equiv), 2,2'-[Ru(MeO-Phtpy)(bpy)Cl]Cl:
			over 3h; the flask was covered by aluminium foil to protect bipyridine (1 equiv), LiCl (6 equiv) were added to Starting materials: [Ru(MeO-Phtpy)Cl 3 ] (335
	75% EtOH/25% H 2 O mixture (92 mL for 1 mmol of ), followed by Et 3 N (1.6 equiv) addition. The with aluminium foil to protect the complex from irradiation. After the reaction completion an undesired precipitate was immediately filtrated off from the hot solution. The precipitate was washed by ethanol and the filtrate was concentrated under reduced pressure until 1/6 of initial volume and left in the fridge over 2 h. The obtained precipitate was filtrated off and rinsed with aqueous HCl solution (3M) mg, 0.61 mmol), 2,2'-bipyridine (96 mg, 0.62 mmol), LiCl (146 mg, 3.5 mmol), Et 3 N (138 the complex from radiation. [Ru(FCCT)Cl 3 ]: mixture was refluxed over 3h; the flask was covered μL, 1 mmol), 75% EtOH/25% H 2 O (56 mL).
	Starting materials: (E)-4'-(2-(9,9-dihexyl-(until the colorless drops of filtrate), a small amount of chilled EtOH and diethyl N Cl
	9H-fluoren-2-yl)vinyl)-2,2':6',2''-terpyridine ether. The product was dried under the vacuum to yield purple solids. N Ru Cl
	C 6 H 13 C 6 H 13			N	Cl	FCCT (216 mg, 0.364 mmol), RuCl 3 •xH 2 O
	[Ru(FCCT)(bpy)Cl]Cl:			(Ru: 40-49%; 96 mg), EtOH (22 mL).
	Yield -262 mg (0.327 mmol, 90%). N Cl	Cl	Starting materials: [Ru(FCCT)Cl 3 ]
				N	Ru N	(262 mg, 0.33 mmol), 2,2'-
	[Ru(FCC3T)Cl 3 ]: C 6 H 13 C 6 H 13			N	N	bipyridine (51 mg, 0.33 mmol),
				N	Cl	Starting	materials: LiCl (77 mg, 1.80 mmol), Et 3 N (74 4'-((9,9-dihexyl-9H-
	fluoren-2-yl)ethynyl)-2,2':6',2''-terpyridine μL, 0.52 mmol), 75% EtOH/25% H 2 O (30 mL). Yield -208 mg (0.23 mmol, 69%). N Ru Cl
	C 6 H 13 C 6 H 13			N	Cl	FCC3T (214 mg, 0.36 mmol), RuCl 3 •xH 2 O
	(Ru: 40-49%; 91 mg), EtOH (30 mL). Yield -169 mg (0.34 mmol, 58 %).

  in water. The

	mixture was left in the fridge for 2 h. The obtained precipitate was filtrated off, rinsed
	N with a small amount of cold EtOH and diethyl ether. The complex was dried under NO 2 Cl
	vacuum.	N	Ru N
	C 6 H 13 C 6 H 13		N	N
	[Ru(FCCT)(bpy)NO](PF 6 ) 3 :
					Starting	materials:
					[Ru(FCCT)(bpy)NO 2 ]Cl (60 mg,
					0.064 mmol), HCl (12M, 6.9 mL,
			N	NO 2	Cl	83.8 mmol), EtOH (21 mL). Yield
	-53 mg (0.041 mmol, 63%).	N	Ru N
	C 6 H 13 C 6 H 13		N	N
	[Ru(FCC3T)(bpy)NO](PF 6 ) 3 :
					Starting	materials:
					[Ru(FCC3T)(bpy)NO 2 ]Cl (72 mg,
					0.078 mmol), HCl (12M, 8.3 mL,
	N -68 mg (0.051 mmol, 66%). NO 2 N Ru N O	Cl	63.2 mmol), EtOH (16 mL). Yield
	N	N
	[Ru(MeO-Phtpy)(bpy)NO](PF 6 ) 3 :
				Starting	materials:	[Ru(MeO-
				Phtpy)(bpy)Cl]Cl (390 mg, 0.58 mmol),
				NaNO 2 (402 mg, 5.83 mmol), 75% EtOH/25%
				H 2 O (72 mL). Yield -357 mg (0.53 mmol,
	90%).

Cl

support from the French government, Ukrainian government and University Paul Sabatier are gratefully my thanks to Dr. Isabelle Sasaki, whose pieces of advice were always helpful in the synthetic part of my work. And I also must point out a big help that Marine Tassé kindly provided every time there was a technical question in the laboratory work. My thanks to Mathilde Bocé, Hasan Mohammed and Max Roose for creating a friendly work atmosphere in the laboratory. A big part of the work has been done with the facilities and opportunities provided by researchers from Mexico. I appreciate an invaluable help of Professor

ONO

The reduction of the ester 4.24 with diisobutylaluminum hydride leads to the formation of an alcohol 4.25, which under oxidation converts to aldehyde 4.26. A similar transformation for compound 4.9 (analogue of compound 4.24 without dimethylamino) readily occurs. However, the reduction and further oxidation of compound 4. 24 is not so easy to perform. According to the methodology compound 4.25 is not to be purified and after being isolated from the reaction mixture, it is introduced in the next step with possible impurities present therein. This procedure reduces the possibility of side reactions of this allyl alcohol possible when it is exposed to the air. In the analogous case of the synthesis of the FCCT compound, an allyl alcohol obtained by the reduction of the corresponding ester was dissolved in CHCl 3 and oxidized with a manganese(IV) oxide that resulted in the formation of a desired aldehyde with a good yield. However, even during a short-term exposure of the compound 4. 25 to the air, it undergoes certain transformations that are easy to observe with the help of thin-layer chromatography (TLC). Quickly, instead of one pale yellow with blue fluorescence spot, corresponding to the alcohol 4.25 another one appears, having a slightly lower value of R f . The subsequent oxidation of the mixture of these two products leads to the formation of the desired aldehyde 4.26 and another product. Moreover, the ratio Scheme 5.1. The synthesis of the ligand 4'-(4-metoxyphenyl)-2,2':6'2''-terpyridine and the mechanism of the reaction.

The complex [Ru II (MeO-Phtpy)(bpy)(NO)](PF 6 ) 3 was obtained in 4 steps, similar to the complexes with FCCT and FCC3T ligands, the synthesis of which is described in section 4 (scheme 4.7). The use of 2D-NMR spectroscopy techniques, in peaks show some broadening, but it's small and it confirms the absence of any paramagnetic Ru III complex. The most noticeable evolution in Figure 1 is the shift of a peak tentatively attributed to traces of water from 2.13 ppm in the initial solution to 6.85 ppm after 155 minutes of irradiation. An explanation for such a change may be the change of the acidity of the solution, which is probably caused by the formation of derivatives of nitrogen in higher oxidation stages (in particular nitrite and nitrate anions), as a result of the oxidation of nitrogen monoxide by the air and the interaction with water traces which are inevitably present in the solvent.

No attempts were made to deoxygenate and to dry the solvent. As an example of possible transformations, the following chemical reactions could be proposed:

either by UV visible spectroscopy or NMR spectroscopy during a direct experiment on the release of nitrogen monoxide from the ruthenium-nitrosyl complex. This fact indicates that the formation of such a cation occurs during some time after irradiation.

Interestingly, the structure of the obtained nitro-derivative or rather 3-nitro-4methoxyphenyl substituent is similar to the product of tyrosine amino acid nitration in living organisms.

As described in section 1.2, the formation of various reactive nitrogen species (RNS) capable of oxidizing and nitrating biomolecules takes place in tissues in the presence of nitric oxide and high concentrations of reactive oxygen forms. Such RNS are peroxynitrite anion, nitrogen(IV) oxide and some others. Although several hypothetical mechanisms for nitration of the amino acid residues of tyrosine are proposed, all of them suggest a radical mechanism of the process. 150,151 One of the possible ways of nitration is shown in Figure 5.12. 151 Given that the methoxyphenyl substituent present in the MeO-Phtpy ligand cannot form a stable radical particle, the radical mechanism of the formation of the cation shown in Figure 5.11 is hardly probable. Possibly, nitration could occur through the mechanism of aromatic electrophilic substitution. In this case nitration could be attributed to the compounds of nitrogen in higher oxidation states, the presence of which in the system is confirmed by the presence of nitrate anions in the crystalline structure of the main photoproduct.

Compound

Summary of thesis

The work "Two-photon induced photorelease of nitric oxide from rutheniumnitrosyl complexes containing ligands with various push-pull capabilities" was devoted to the revealing of main factors that determine the efficiency of ruthenium-nitrosyl complexes in two-photon absorption (TPA) and to the improvement of TPA cross-section through modification of the ligands nature and their structure.

Starting from complexes previously obtained by the research group of Prof. I.

Malfant we have modified their structure in several directions. It was shown that substitution of monodentate ligands by 2,2'-bipyridine in ruthenium complexes with nitrosyl ligand leads to a slight increase of their TPA cross-section, however this modification decreases the quantum yield of the nitric oxide photorelease.

Synthetic part of the work was mainly aimed at the modification of the ligand 4'-(9H-fluoren-2-yl)-2,2':6',2''-terpyridine. The elongation and flattening of the conjugation path could improve the polarizability of the ligand and the "push-pull" character of the complex. This subsequently results in an increased efficiency of the compounds in TPA that was confirmed in the current work. Insertion of double bond between two parts of the ligand leads to the enhancement of the TPA crosssection by 20%, whereas the triple bond appears better linker leading to 36% improved efficiency of complexes in TPA. Another parameter of compounds, sensitive to the structural modifications, is the difference in dipole moments between the ground and excited states of the molecules. It deserves particular attention whereas it enters the expression of the TPA efficiency as the criterion of "push-pull" character of the molecule. With the purpose of increasing this difference we put as a goal the synthesis of the complexes with ligands bearing donating dimethylamino-groups. Having optimized the methodology of ligands syntheses, we, however, found out that usual way of complex synthesis in this case has not resulted in the desired complex obtention. During the second step of the 204 ruthenium-nitrosyl compound synthesis an incorporated dimethylaminogroup undergoes the oxidation process with its subsequent demethylation.

However, having obtained a series of easier accessible complexes with groups displaying different donating abilities, we were able to discover some tendency.

These complexes contain phenyl rings, carrying functional groups starting from withdrawing nitro-to donating metoxy-and dimethylaminogroups. It was shown that while accepting or neutral groups didn't show any significant influence on the TPA cross-sections of complexes, donating moieties increased it with the highest value of 154 GM observed for complex with 4'-(4-methoxyphenyl)-2,2':6',2''terpyridine ligand. Thus the observation has confirmed the initial hypothesis that increasing of the difference in dipole moments between the ground and excited state would lead to an enhanced efficiency of complexes in TPA.

In the current work theoretical calculations on the basis of density functional theory (DFT) are widely involved. Apart from studying the ability of complexes to release NO under irradiation a theoretical investigation of their nonlinear optical properties was made. In order to improve the conjugation and the length of theconjugation system we have assessed the effect of the fluorenyl-fragment substitution by 22 different heterocyclic analogues having similar tricyclic skeleton and containing donating Nitrogen atom in the system. It was shown, that in spite of the fact that such modification doesn't lead to a desired improvement, such compounds could be indeed interesting as nonlinear optical materials.

The structure of the photoproduct and ruthenium oxidation states are discussed in details. In contrast to photoproducts previously observed, complexes having five pyridine rings in the coordination sphere of metal form Ru(II) products during the process of NO-photorelease, whereas the formation of NO-radical is confirmed by EPR-spectroscopy.

CONTENU PRINCIPAL

Dans l'introduction le contexte du travail est expliquée, le but et les objectifs de l'étude sont énoncés avec la signification des résultats obtenus.

Le premier chapitre de la thèse est consacré à la présentation de l'avancement de la recherche sur le sujet de la thèse.

(Figure 1).