Simon Enjalbert
email: simon.enjalbert@uphf.fr

Suzana Kahn

Frédéric Vanderhaegen
email: frederic.vanderhaegen@uphf.fr

Concepts and models about smart urban transport control systems for city resilience

Keywords: Smart city, Urban transport control system, Design, modelling and analysis of Human Machine Systems, Resilience of Human Machine Systems

The work presented in this paper concerns the control and the efficient assessment of transport systems of a city by studying the impact of climate change, energy supply or human behaviour on different modalities of mobility. Concepts from Human Machine Systems and from green, eco, sustainable, and smart cities, aggregated on resilient city concept, should be an inspiration to develop model for urban transport control systems. A state-of-the-art is proposed to discuss about these concepts and try to determine criteria which should be selected in such process. A first framework based on cooperation and learning concepts is then presented and still must be improved.

INTRODUCTION

Projected climate change for the upcoming decades represents a major challenge to be faced by humanity in the twenty-first century and climate changes expose cities to sea levels rising, changes in the frequency and intensity of storms, increased precipitation and ocean temperatures, among other negative impacts. Each of these factors poses risks to the human population. Today, more than half of the world's population (3.6 billion) lives in cities and by 2050, the urban population is expected to grow to 5.6-7.1 billion, or 64-69% of world population The increasing of people in cities implies the design of infrastructures and supports capable to prevent, recover or mitigate the occurrence or the consequence of economic, social or environmental obstacles, aggressions or perturbations. To do so, different concepts as green city, sustainable city, smart city, or resilient city are developed in order to face social, economic and environmental impact of such phenomena or other disorders. One of the main challenging aspects for city resilience is the facilitation of the mobility of people whatever the conditions of use. This paper proposes a way to design such a support dedicated to the smart control of urban transport system based on constraints such as human and consumption factors. The sections 2 and 3 of the paper present definitions and concepts about Human Machine Systems (HMS) resilience and city resilience respectively. Section 4 introduces the proposed architecture for a smart urban transport control system based on electrical energy and human driver constraints. An example illustrating the feasibility of the proposal is considered.

CONCEPTS ABOUT HUMAN MACHINE SYSTEMS RESILIENCE

Resilience relates to the ability of a system or a human to avoid any loss of auto-control or self-control despite the occurrence of whatever disturbances [START_REF] Vanderhaegen | Towards increased systems resilience: new challenges based on dissonance control for human reliability in cyber-physical&human systems[END_REF]). It is linked with different kinds of ability and criterion given in Table 1. On ecology or biology viewpoints, it relates to the survival of species when they undergo attacks or aggression [START_REF] Holling | Resilience and stability of ecological systems[END_REF]; [START_REF] Orwin | New indices for quantifying the resistance and resilience of soil biota to exogenous disturbances[END_REF]; [START_REF] Watanabe | Resilience as a source of survival stategy for high-technology firms experiencing megacompetition[END_REF]; Pérez-España and Arreguin-Sánchez ( 2001)). On psychology or medicine domains, it depends on individual ability to recover from a physical or psychological shock or trauma [START_REF] Engle | Child development: Vulnerability and resilience[END_REF]; [START_REF] Goussé | Apport de la génétique dans les études sur la résilience: l'exemple de l'autisme[END_REF]). From an engineering point of view, it is the ability to manage any unstable system face to any events by recovering it as quickly as possible [START_REF] Hollnagel | Resilience engineering: Concepts and precepts[END_REF]; [START_REF] Wreathall | Properties of resilient organizations: an initial view[END_REF]). Other engineering approaches consider that a resilient system can prevent, absorb, recover or mitigate any disorder ( [START_REF] Vanderhaegen | Toward a model of unreliability to study error prevention supports[END_REF]; [START_REF] Ruault | 2.6. 2 sociotechnical systems resilience[END_REF]), can successfully control unprecedented situations [START_REF] Ouedraogo | How to learn from the resilience of humanmachine systems[END_REF]; [START_REF] Enjalbert | A hybrid reinforced learning system to estimate resilience indicators[END_REF]), or can successfully self-organize interconnected system components to react to any breakdown [START_REF] Martinson | Resilience in a transportation system: A whole system approach[END_REF]). Finally, in a more general viewpoint, the resilience of isolated or interconnected systems relates to the acceptable control of their stability or instability by taking into account a single reference or several references of acceptability [START_REF] Vanderhaegen | Cooperation and learning to increase the autonomy of adas[END_REF][START_REF] Vanderhaegen | A rule-based support system for dissonance discovery and control applied to car driving[END_REF][START_REF] Vanderhaegen | Towards increased systems resilience: new challenges based on dissonance control for human reliability in cyber-physical&human systems[END_REF]). A sustainably stable system state can be an obstacle to react efficiently to unknown disturbances due to hypovigilance for instance. On the other hand, the regular occurrence of unstable states can train the system to control this event, and to go back to a previous stable state, to discover new stable states or new strategies to accept and manage sustained instability.

This requires resilience ability properties to achieve such goals. Criteria of stability aim at detecting an instantaneous or sustained state of system stability or instability, and the acceptability ones to determine if it is an acceptable or unacceptable state regarding factors as safety, performance, workload, attention or comfort for instance. Criteria about plasticity related to the ability to adapt to changes and transform the system structure to maintain the achievement of its functions entirely or partially. Plasticity gathers then criteria as:

• ability to perform these goals (i.e., performability),

• ability to recover from a perturbation (i.e., recovery),

• ability to discover and control dissonance when conflicts between contradictory viewpoints about acceptability occur. • ability to cooperate (i.e., co-operability) in order to share a problem-solving due to a perturbation and find a joint optimal solution • ability to learn (learnability) to handle humansystems knowledge.

These abilities and criteria about system resilience can be applied for city resilience. The next section focuses on the existing concepts around the city resilience achievement.

CONCEPTS ABOUT CITY RESILIENCE

Contributions on city resilience can take into account criteria about resilience engineering and related to green city, sustainable city, smart city or resilient city in Table 2. They concern different dimensions about infrastructures, services, environment, or health. Green cities or eco-cities focus on ecological dimensions related to environmental factors and their impacts on human life quality, health and pollution [START_REF] Busch | The green city index-a summary of the green city index research series[END_REF]). Sustainable cities take mainly into account the sustainable social, environmental and economic impact of city services and infrastructures [START_REF] Ibrahim | Theoretical review on sustainable city indicators in malaysia[END_REF]; [START_REF] Batten | Sustainable cities index 2016[END_REF]. Smart cities include smart city components to guarantee mobility, services, security, safety and autonomy [START_REF] Gaur | Smart city architecture and its applications based on Table 3. Examples of models for smart urban transport control system Model Principe Resilience criteria References Mechanical engineering approaches Fluid flow modeling Decongestion[END_REF]; De Wijs et al. ( 2017)). They aim at designing connected city that use technologies of communication and information to produce data, to analyze them, and to improve city efficiency in terms of criteria as quality, performance, interaction between urban services, reduction of economic costs and of resource consumption, increasing of interaction between citizens with the city administrative services. Resilient cities usually gather the dimensions of the other concepts, but integrate additional ones related to city management or city governance for instance (Da Silva and Morera (2014); [START_REF] Sugahara | Energy and resilient cities[END_REF]; [START_REF] Zheng | Development as adaptation: Framing and measuring urban resilience in beijing[END_REF]). They are cities that have the ability to absorb, recover and prepare for future economic, environmental, social and institutional disorders.

When considering the resilience of cities, account should be taken on the increased climate risks as the suppression of ecosystems, triggered by urban growth. This is one of the main factors reducing the resilience of cities, making them more vulnerable to current and future problems, which may be accentuated by rising heat islands, air pollution and flooding. Thus, climate variations may exacerbate pressures already existing. The often already chaotic urban traffic tends to become even worse. Impacts on transport infrastructure are also expected due to sea level rise, temperature variations, precipitation and the occurrence of extreme weather events (including heavy rainfall), which may accelerate the deterioration of structures, increase the risk of interruptions traffic and accidents, with consequent impact on the economy of cities. These episodes are often accompanied by flooding, whose urban drainage system cannot contain, and which result in blockage from urban roads and property damage, among other disorders. All of these potential risks to the proper functioning of urban transport systems must be considered when designing a smart control system that aims to make the city more resilient. All the city resilience based concepts propose dimensions related to urban transportation systems and imply sustainability based criteria. The urban transport sustainability depends on factors such as transport system usability, ecological impact, economic impact, traffic flow, passenger comfort, system safety, passenger accessibility, or quality services.

In section 4, contributions to city resilience based on a framework including Human-Machine Systems concepts depicted in section 2 will be proposed.

A FRAMEWORK FOR SMART URBAN TRANSPORT CONTROLLING SYSTEMS FOR CITY RESILIENCE

The design of smart urban transport systems requires high level of adaptability by taking into account static and dynamic constraints such as road, rail, maritime or pedestrian infrastructures, mobility needs, or services availability. The proposed smart urban transport system takes into account ecological and economic criteria by assisting mobility to optimize energy consumption related to current human behaviours. Some obstacles to the design of smart realtime infrastructure control systems are for instance the lack of instrumentation on infrastructure, the lack of efficient automation and control supports, lack of autonomy on vital supplies, the lack of efficient shareable data model due to the design of closed systems, the lack of relevant reporting without adapted focus on trustworthiness, the lack of real-time data optimized for different classes of user or the inability to simulate, model and anticipate the effects of change.

Several models exist for such designing smart urban transport control systems by taking into account resilience criteria, as shown in Table 3 [START_REF] Vanderhaegen | Cooperation and learning to increase the autonomy of adas[END_REF][START_REF] Vanderhaegen | A rule-based support system for dissonance discovery and control applied to car driving[END_REF][START_REF] Vanderhaegen | Towards increased systems resilience: new challenges based on dissonance control for human reliability in cyber-physical&human systems[END_REF] red resources to solve a problem and manage alone resilience criteria such as decongestion, efficiency, comfort, safety, flexibility, ecology or economy. However, components from a given transport mode are sometimes insufficient to achieve resilience criteria and require the support of other components from other transport modes. To do so, interaction supports are required to perform activities as co-learning or cooperation [START_REF] Vanderhaegen | Cooperation and learning to increase the autonomy of adas[END_REF]).

Cooperation activities between systems imply three main prerequisites: the required knowledge to solve any problem, the availability of the required technical and human resources to apply this knowledge, and the possibility to act by these resources [START_REF] Vanderhaegen | Towards increased systems resilience: new challenges based on dissonance control for human reliability in cyber-physical&human systems[END_REF]). Learnability and co-operability are then the minimum requirements for smart urban transport system in term of city RC Resilience Criteria. The controlled of these criteria can be done locally or globally by a given T M Transport Mode or by interacting with OT M Other Transport Modes in Figure 1. Each component of a T M or OT M has its C Competency, its A Availability and its P Possibility to act regarding its prescriptions and its available interaction supports.

As these prerequisites are dynamic, future smart transport system models have to be designed by applying the humansystems inclusion concept [START_REF] Vanderhaegen | Pedagogical learning supports based on human-systems inclusion applied to rail flow control[END_REF]). This approach considers both the automation-supported human and human-supported automation processes to take advantage of both human and machine abilities to treat normal and abnormal events. Transport system component should be able to learn alone (i.e., self-learning or auto-learning abilities), from the other or with the other connected components. When unknown, uncertain or unprecedented situations occur, behaviours as trial-anderror or wait-and-see can be implemented in the system learning process [START_REF] Vanderhaegen | A multiviewpoint system to support abductive reasoning[END_REF]). To do so, different learning strategies can be applied in order to merge feedback data about controlled situations or to create new ones [START_REF] Polet | Iterative learning control based tools to learn from human error[END_REF]; [START_REF] Vanderhaegen | Reinforced learning systems based on merged and cumulative knowledge to predict human actions[END_REF]; [START_REF] Enjalbert | A hybrid reinforced learning system to estimate resilience indicators[END_REF]). Such learning process is not devoid of possible dissonances when conflicts on knowledge exist between human and machine components of the system [START_REF] Vanderhaegen | Dissonance engineering: a new challenge to analyse risky knowledge when using a system[END_REF][START_REF] Vanderhaegen | A rule-based support system for dissonance discovery and control applied to car driving[END_REF][START_REF] Vanderhaegen | Towards increased systems resilience: new challenges based on dissonance control for human reliability in cyber-physical&human systems[END_REF]). Therefore, the knowledge of each component has to be dynamic in order to recover any possible inconsis-tency or to take into account knowledge discover. The management of resilience criteria includes several classes of dynamic constraints as human factor based constraints, energy consumption constraints or climate effect based constraints. Smart urban transport system models have then to be able to support human decision to optimize energy consumption, to sustain mobility services despite strong climate effects, or to learn from human behaviours in two ways: 1) when the human drivers do not respect the initial advices, obliging the decision support tools to reassess new advices, and 2) when the support systems can improve their knowledge taking into account feedback from human behaviours.

CONCLUSION

In this paper, the authors try to develop a framework for modelling a smart urban control system. The presented model should be improved taking into account energy and human constraints, and also to be able to learn form unexpected whatever the conditions of use of city transports. City and Human Machine Systems resilience concepts seem promising to be used to develop such a new resilient city model regarding transport control systems. This work should to be led during PhD collaboration between french and Brazilian universities and is expected to be started as soon as possible to face acceleration of climate change events and growing of city population.

Table 1 .

 1 Abilities and criteria about resilience

	. Mechanical engineering appro-
	aches simulate traffic flow by making analogies with fluid
	or gas-kinetic characteristics (Catalin et al. (2012); Utama
	et al. (2016); Tampère et al. (2002); Ngoduy (2012)). Bio-
	inspired models aim at modelling the behaviours of species
	as ants or birds to avoid collision and maintain movement
	(Kammoun et al. (2011); Jabbarpour et al. (2014); Li and
	Huang (2019); Antoniou et al. (2009)). Human-machine
	approaches are automation-supported human based ap-

proaches (La

[START_REF] Delfa | Eco-driving command for tram-driver system[END_REF]

) or human-supported automation based ones

[START_REF] Vanderhaegen | Pedagogical learning supports based on human-systems inclusion applied to rail flow control[END_REF]

).

Resilience criteria can be controlled alone or by interacting with other connected components of transport systems. Their smartability supposes that they have the requi-

Table 2 .

 2 Concepts about resilient city

	Concepts	Main associated dimensions	Associated transport dimensi-	Resilient transport	References
			ons				criteria
	Green city, eco-city	CO2 emissions, energy, buil-	Use of non-car transport, size	Usability, Ecology,	Busch (2012)
		dings, land use, transport, wa-	of non-car transport, green	Decongestion
		ter and sanitation, waste ma-	transport promotion, conges-
		nagement, air quality, environ-	tion reduction policies
		mental governance
	Sustainable city	Population, housing, economy,	Control of safety, comfort, ef-	Safety,	Comfort,	Ibrahim et al.
		utility and infrastructure, pu-	ficiency in terms of economy	Efficiency,	(2015)
		blic facilities, environment, so-	and power usage of transport	Economy, Ecology
		ciology and social impact,	system, minimize the environ-
		land use, tourism and heri-	mental pollution of transport
		tage, transportation, manage-	system
		ment and finance
		People, planet, profit	Transport	infrastructure,	Performance, Eco-	Batten and Ed-
			performance	measurements,	logy	wards (2016)
			transport energy consumption,
			air pollution of transport
		Environmental, social, econo-	Users of mass transit, average	Performance, Eco-	Tanguay et al.
		mic, livable, viable, equitable	distance in km/per capita/year	logy, Economy	(2010)
			traveled for all means of trans-
			port combined, rate of death
			and injuries caused by traffic
			accidents per 1000 inhabitants
		Transport: environmental, eco-	pollution, energy consumption,	Target relevance,	Haghshenas
		nomic, social	land consumption, cost for go-	data	availability	and	Vaziri
			vernment, direct trip cost for	and measurability,	(2012);
			user, indirect trip cost for user,	validity, sensitivity,	Haghshenas
			safety, accessibility, variety	transparency,	et al. (2015)
							independent,
							standardized
	Smart city	Economy, people, governance,	Transport accessibility, sus-	Accessibility, Sus-	De Wijs et al.
		mobility, environment, living	tainable, innovative and safe	tainability, Innova-	(2017)
			transport systems		tion, Safety
		Environment, transports, in-	Smart traffic control, Intelli-	Smartability, Sus-	Gaur et al.
		dustries, administration, office	gent drive, smart transport in-	tainability	(2015); Girardi
		and residential building, secu-	frastructure				and Temporelli
		rity and energy						(2017)
		Transport	Noise and vibrations, Acci-	Representation,	Joumard et al.
			dents, air pollution, soil and	Operation, Policy	(2011)
			water pollution, impcats on	application
			land, Non-renewable resource
			use and waste handling, Green-
			house effect
	Resilient city	Economy, society, ecology, in-	Traffic	congestion,	Urban	Decongestion, Sa-	Zheng et al.
		frastructure	transport risk management	fety, Performance	(2018)
		Governance, society, environ-	Sustainable urban transport	Sustainability, Re-	Sugahara
		ment, economy	development, adequate and re-	liability	and Bermont
			liable transport infrastructure		(2016)
		Leadership & strategies, health	Diverse and affordable trans-	Flexibility,	Da Silva and
		& well-being, infrastructure &	port network, effective trans-	Operationability,	Morera (2014)
		ecosystems, economy & society	port operation and mainte-	Maintainability,
			nance for quality and safety	Quality, Safety

ACKNOWLEDGEMENTS

The present research work has been supported by: The European Community, The French Ministry of Higher Education and Research, And The Hauts-de-France Region. The authors gratefully acknowledge the support of these institutions.


Martin Kos

Rafael Rodríguez

Jan Storch

Jan Sýkora

Elsa Caytan

Marie Cordier

Ivana Císařová

Nicolas Vanthuyne

Gareth Williams

Jaroslav Žádný

Jan Syḱora

Ivana Císarǒvá

J A Gareth Williams

Jaroslav Z ̌ádny

Vladimír Církva

Jeanne Crassous

Enantioenriched Ruthenium-Tris-Bipyridine Complexes Bearing One Helical Bipyridine Ligand: Access to Fused Multihelicenic Systems and Chiroptical Redox Switches

published or not. The documents may come   L'archive ouverte pluridisciplinaire

■ INTRODUCTION

Helicenes are a unique class of polyaromatic compounds formed by ortho-fused aromatic rings that adopt an inherently chiral helical structure. 1 Generally, the enantiomers are conformationally stable and separable by chiral HPLC, if the number of aromatic rings is ≥6 or if the "bay positions" are substituted with bulky substituents in [5]-or [4]helicenes. 2 The extended conjugation over the aromatic rings, together with helical chirality, gives rise to unique chiroptical properties such as high molar rotation, strong electronic circular dichroism (ECD), and circularly polarized luminescence (CPL). 3 The introduction of heteroatoms such as nitrogen within the helical scaffold gives access to azahelicene derivatives with tuned electronic and optical properties. 3b This simple modification is sufficient to trigger exceptional properties such as improved charge transport and enhanced photophysical and chiroptical properties. Azahelicenes are thus appealing in diverse applications such as chiral dopants in organic light-emitting diodes (OLEDs), 4 chiral charge transporters in organic field-effect transistors (OFETs), [START_REF] Yang | Induction of Circularly Polarized Electroluminescence from an Achiral Light-Emitting Polymer via a Chiral Small-Molecule Dopant[END_REF] and spin filters for spintronics. [START_REF] Kiran | Helicenes-A New Class of Organic Spin Filter[END_REF] Moreover, azahelicenes can be applied as efficient chiral ligands in coordination chemistry. 3b,7 In the past decade, we and others have focused on the development of new helical architectures bearing bidentate or tridentate coordinating moieties that, upon coordination to a variety of metal ions, lead to the formation of unique structures with remarkable optical and electronic properties. 1,3,7 Interestingly, appropriate engineering of the helicene ligand framework can generate multihelicenic systems through metal ion coordination, making this strategy an alternative to tedious, more conventional organic syntheses. 7c This approach represents an effective way to obtain materials that display circularly polarized phosphorescence for application as chiroptical switches [START_REF] Saleh | Acid/Base-Triggered Switching of Circularly Polarized Luminescence and Electronic Circular Dichroism in Organic and Organometallic Helicenes[END_REF] or circularly polarized OLEDs (CP-OLEDs). 9 In this context, the ubiquity and versatility of bidentate 2,2′-bipyridine (bipy) in coordination chemistry [START_REF] Kaes | The Most Widely Used Ligand. A Review of Molecules Comprising at Least Two 2,2'-Bipyridine Units[END_REF] renders helicenes that incorporate this unit as a particularly appealing target.

A number of synthetic strategies have been reported for the preparation of helicene-bipy ligands, leading to products summarized in Figure 1. The main routes are the Stille-Kelly reaction of a dibromo derivative (to give A), [START_REF] Chen | Helical Chiral 2,2′-Bipyridine N-Monoxides as Catalysts in the Enantioselective Propargylation of Aldehydes with Allenyltrichlorosilane[END_REF] [2+2+2] cycloaddition of triynes (leading to B), [START_REF] Klívar | Asymmetric Synthesis of Diastereo-and Enantiopure Bioxahelicene 2,2′-Bipyridines[END_REF] C-H activation of an N-oxide (to generate C), [START_REF] Kaneko | Synthesis of Azahelicene N-Oxide by Palladium-Catalyzed Direct C-H Annulation of a Pendant (Z)-Bromovinyl Side Chain[END_REF] and Mallory photocyclization of stilbenes (in the synthesis of D, E, and F). [START_REF] Saleh | Acid/Base-Triggered Switching of Circularly Polarized Luminescence and Electronic Circular Dichroism in Organic and Organometallic Helicenes[END_REF][START_REF] Isla | Bis-4-Aza[6Helicene: A Bis-Helicenic 2,2′-Bipyridine with Chemically Triggered Chiroptical Switching Activity[END_REF]15 The coordination chemistry of mono-and bis-helicenic bipyridine ligands (D and E, respectively) and of helicene-bis-bipyridine (F) to Pt(II), [START_REF] Saleh | Acid/Base-Triggered Switching of Circularly Polarized Luminescence and Electronic Circular Dichroism in Organic and Organometallic Helicenes[END_REF] Zn(II), [START_REF] Isla | Bis-4-Aza[6Helicene: A Bis-Helicenic 2,2′-Bipyridine with Chemically Triggered Chiroptical Switching Activity[END_REF] Re(I), 15 Ru(II), [START_REF] Saleh | Enantio-Enriched CPL-Active Helicene-Bipyridine-Rhenium Complexes[END_REF] and Ln(III) 17 has been studied, giving access to efficient CPL-active chiral materials, chiroptical switches, and chiral single molecular magnets (SMMs).

Among the many metal complexes of bipyridines, those of ruthenium(II) have attracted remarkable attention over the last five decades. [Ru(bipy) 3 ] 2+ and its derivatives have an almost unique combination of properties that include high chemical stability, reversible oxidation and reduction, lowest-energy singlet and triplet excited states of metal-to-ligand chargetransfer ( 1,3 MLCT) character, excited-state reactivity, and room-temperature phosphorescence with triplet excited-state lifetimes of hundreds of nanoseconds. 18 They have found applications in various branches of chemistry such as photocatalysis, electrochemistry, and electrochemiluminescence. 18,19 Nevertheless, despite the vast development of chiral 2,2′-bipyridine ligands in homogeneous catalysis, 20 there are only limited reports on [Ru(bipy) 3 ] 2+ derivatives that bear centrally chiral ligands 19b and no report of such a complex incorporating a ligand with helical chirality. Some of the authors of the present work recently reported a novel method [START_REF] Kos | Oxidative Photocyclization of Aromatic Schiff Bases in Synthesis of Phenanthridines and Other Aza-PAHs[END_REF] to prepare new [n]helicenes with different numbers of aromatic units (n = 4, 5), on the basis of a photocyclization similar to Mallory's reaction but with imines instead of olefins. Until recently, this method was still very rare, 22 and the preparation of helicenes by this methodology was limited to a few examples formed in poor yields (2-10%). 23 Superior reaction efficiency has recently been achieved on corannulene-based imines. [START_REF] Ghosh | Synthesis of Azahelicenes through Mallory Reaction of Imine Precursors: Corannulene Substrates Provide an Exception to the Rule in Oxidative Photocyclizations of Diarylethenes[END_REF] Here, we report the synthesis of a novel family of helical ligands (L) bearing either one (6a-d) or two (10a,b) bipy units via oxidative photocyclization of aromatic imines (Figure 2). In these ligands, the bipy moiety is grafted in a position that is different from previously reported bipyridine helicenes [START_REF] Saleh | Acid/Base-Triggered Switching of Circularly Polarized Luminescence and Electronic Circular Dichroism in Organic and Organometallic Helicenes[END_REF][START_REF] Chen | Helical Chiral 2,2′-Bipyridine N-Monoxides as Catalysts in the Enantioselective Propargylation of Aldehydes with Allenyltrichlorosilane[END_REF][START_REF] Klívar | Asymmetric Synthesis of Diastereo-and Enantiopure Bioxahelicene 2,2′-Bipyridines[END_REF][START_REF] Kaneko | Synthesis of Azahelicene N-Oxide by Palladium-Catalyzed Direct C-H Annulation of a Pendant (Z)-Bromovinyl Side Chain[END_REF][START_REF] Isla | Bis-4-Aza[6Helicene: A Bis-Helicenic 2,2′-Bipyridine with Chemically Triggered Chiroptical Switching Activity[END_REF][15] with a 2-pyridyl pendant at position 6 of the outer groove of a 5-azahelix. This feature offers enough room for further coordination of bulky metallic units such as Ru(bipy) 2 2+ . Enantioenriched complexes of the general formula [RuL(bipy) 2 ] 2+ (11a,c, L = 6a,c) and [Ru 2 L′(bipy) 4 ] 4+ (12, L′ = 10b) with defined stereochemistry have thereby been prepared in this work. We show that, upon coordination, unprecedented multihelicenic fused systems 25 incorporating Ru ions are produced. In most cases, their topology and stereochemistry are dictated by the ruthenium center itself. Furthermore, taking advantage of their redox properties and strong ECD response, these complexes were characterized as redox-triggered chiroptical switches, promising materials for possible application in molecular electronic or display technologies. 26 ■ RESULTS AND DISCUSSION Synthesis of Helical Bipyridine Ligands. The efficient preparation of phenanthridines/aza[n]helicenes (n = 4, 5) bearing a pendant phenyl group ortho to the nitrogen atom was recently described by some of the authors through a photocyclization reaction of aromatic imines. [START_REF] Kos | Oxidative Photocyclization of Aromatic Schiff Bases in Synthesis of Phenanthridines and Other Aza-PAHs[END_REF] In the current study, we extend the method to the preparation of 6-(2pyridyl)-phenanthridine 2 (Scheme 1) and to helical polyaromatic hydrocarbons containing a bipy moiety (Figure 2 and Scheme 2). The photochemical cyclization of imine 1 in the presence of HBF 4 •Et 2 O and TEMPO proceeded nearly exclusively at the unsubstituted phenyl ring and gave 2 in acceptable yield (Scheme 1) with almost no formation of the alternative isomer 2′. The high selectivity of the photocyclization process is due to the electron-withdrawing nature of the pyridine, enhanced by protonation under acidic conditions. The use of TEMPO protected the starting imines from an undesired reduction, while molecular sieves prevented their hydrolysis.

The synthesis of more extended aromatic systems through the photocyclization of 5b was then examined on the milligram scale and monitored by GC-MS analysis (Table 1). Using the conditions optimized for the preparation of phenanthridines (Table 1, Entry 1 21 ), most of the starting material was hydrolyzed to ketone 4b, showing the instability of 5b in the acidic environment under irradiation. In the absence of acid (Table 1, Entry 2), hydrolysis of the imine was suppressed but only traces of helicene 6b were detected in the reaction mixture. Using quartz instead of Pyrex glassware led to an increased conversion of 5b to 6b, but hydrolysis to ketone 4b still prevailed (Table 1, Entry 3). The addition of Ti(OiPr) 4 as a water scavenger was finally found to avoid hydrolysis while promoting almost quantitative conversion of 5b to 6b (Table 1, Entry 4). The reaction on a preparative scale under the same conditions resulted in the isolation of 6b in 65% yield (Scheme 2a).

These optimized conditions were utilized for the preparation of three other helicenes incorporating a bipyridyl unit: 6a, 6c, and 6d (Figure 2 and Scheme 2a). Lithiation of aryl bromides 3a-d and the reaction with 2-cyanopyridine led to ketones 4a-d in high yields. Their reaction with aniline gave imines 5a-d as mixtures of the E/Z-isomers, which were subsequently irradiated in the presence of Ti(OiPr) 4 and TEMPO under an inert atmosphere. Compounds 6a,b,d with five ortho-fused benzene rings were isolated in up to 73% yield while aza [6]helicene 6c was obtained in 48% yield. To the best of our knowledge, this is the first preparation of [n]helicene-bipy by oxidative photocyclization of imines. The product structures were unambiguously confirmed by HRMS and 1 H and [START_REF] Kaneko | Synthesis of Azahelicene N-Oxide by Palladium-Catalyzed Direct C-H Annulation of a Pendant (Z)-Bromovinyl Side Chain[END_REF] C NMR spectroscopy and, for 6b and 6c, X-ray crystallography (Figures 3a andS44, S45 for ORTEP drawings). Both racemic 6b and 6c crystallized in the P1̅ centrosymmetric space group. 6-(2-Pyridyl)-5-aza [6]helicene 6c exhibits a helical shape with a helicity (dihedral angle between the terminal rings) of 47°. There is a mutually anti arrangement of the two N-pyridyl rings that is typical of 2,2′-bipyridines with a dihedral angle of 51.20°.

The same approach was further examined in the photocyclization of analogous diimines giving rise to 10a,b. [START_REF] Hoffmann | Photochemical Reactions Applied to the Synthesis of Helicenes and Helicene-like Compounds[END_REF] The requisite diketones 8a,b were obtained from dibromoarenes 7a,b by lithiation using t-BuLi and subsequent reaction with 2-cyanopyridine (Scheme 2b). Reactions of 8a,b with aniline gave diimines 9a,b. The irradiation of crude 9a,b in the presence of Ti(OiPr) 4 and TEMPO led to diazahelicenes 10a,b in fair yields. Their C 2 symmetry is reflected in simpler NMR spectra (full characterization is given in the Supporting Information). The structure of 10b was also confirmed by Xray diffraction analysis of a single crystal grown by slow diffusion of acetonitrile into a chloroform solution (Figures 3b andS46). Racemic 6,13-bis(2-pyridyl)-5,14-diaza [7]helicene 10b crystallizes in the P1̅ space group: it exhibits a helicity of 35.06°and dihedral angles of the two trans-bipy units of 43.01-43.87°.

[n]Helicenes with n ≥ 6 possess a racemization barrier >150 kJ mol -1 , which enables the (M)-and (P)-enantiomers to be isolated at room temperature. 1,28 Ligands 6c, 10a, and 10b, each formed as racemic mixtures, were separated into their constituent enantiomers by semipreparative HPLC over a Chiralpak IE stationary phase (for details, see the Supporting Information). All enantioenriched samples were obtained with enantiomeric excesses (ee's) between 95% and 99.5% (see the Supporting Information).

Photophysical and Chiroptical Properties of Ligands 6c and 10a,b. The helicene ligands 6c and 10a,b display broad and intense UV-visible (UV-vis) absorption spectra in the 200-400 nm range (Figure 4a, bottom). They are fluorescent in solution at room temperature, as observed for previously described azahelicenes. [START_REF] Saleh | Acid/Base-Triggered Switching of Circularly Polarized Luminescence and Electronic Circular Dichroism in Organic and Organometallic Helicenes[END_REF]15 They display slightly structured emission bands in the blue region of the spectrum (Figure 4b, bottom). As expected, the emission maxima increasingly red shift with increasing conjugation with 10b displaying the lowest energy emission. In CH 2 Cl 2 solution, the structure is more pronounced with the 0,0 vibrational component being the most intense (Figures S51-S53). Under these conditions, the fluorescence quantum yields are of the order of 2-7% (10% for 6a) and corresponding lifetimes are of the order of a few nanoseconds (Table S1), values that are quite typical of aza-aromatics. In a frozen glass at 77 K, the fluorescence (which is marginally blue-shifted compared to room temperature) is accompanied by structured phosphorescence bands at lower energy (Figures S51-S53). This spinforbidden emission from the triplet state is characterized by very long lifetimes of around 1 s (Table S1).

The ECD spectra of the three pairs of enantiomers are displayed in Figure 4a (top part). Ligand (P)-6c shows a strong negative band at 246 nm (Δε = -260 M -1 cm -1 ) and a strong positive one at 330 nm (Δε = +230 M -1 cm -1 ) accompanied by a weaker positive band at 284 nm (Δε = +60 M -1 cm -1 ). Ligand 10a follows a similar pattern with much weaker signals (Δε max ∼ 140 M -1 cm -1 ). Qualitatively, the helical shape of the molecule is disturbed by the presence of the additional pyridyl group, which may explain such a decrease, as a result of the modifications of the magnetic and electric dipolar moments. The main bands in the ECD spectrum of 10b are red-shifted by around 20 nm compared to 6c and 10a and of overall higher intensity. This can be classically explained by the more extended π-conjugation and different helical pitch in heptahelicenes as compared to hexahelicenes. Thus, (P)-10b displays a strong negative band at 263 nm (Δε = -220 M -1 cm -1 ) accompanied by a weaker negative band at 302 nm (Δε = -90 M -1 cm -1 ) and a strong positive one at 349 nm (Δε = +320 M -1 cm -1 ). The polarization of the emitted light was studied by CPL spectroscopy (Figure 4b, top). The (P)-and (M)-enantiomeric pairs of 6c and 10a,b display mirror-image CPL spectra with equal but opposite-sign g lum values recorded around the emission maxima [(P)/(M)-6c: +4.0/-3.7 × 10 -3 ; (P)/(M)-10a: +1.1/-1.2 × 10 -3 ; (P)/(M)-10b: +5.4/-5.4 × 10 -3 ], in line with CPL data of previously investigated bipyridine helicenes (g lum ∼ 10 -3 ). [START_REF] Saleh | Acid/Base-Triggered Switching of Circularly Polarized Luminescence and Electronic Circular Dichroism in Organic and Organometallic Helicenes[END_REF]15 Synthesis and Characterization of Ruthenium Complexes. The preparation of Ru(II) complexes of the [RuL(bipy) 2 ] 2+ and [Ru 2 L′(bipy) 4 ] 4+ ] form (11a,c and 12) was achieved by directly reacting the helicene-bipy ligands L with Ru(bipy) 2 Cl 2 in a polar solvent. 29 Such a reaction of achiral [4]helicene 6a with racemic Ru(bipy) 2 Cl 2 , followed by metathesis of the chloride anion to hexafluorophosphate, yielded a racemic mixture of (Δ)-and (Λ)-[Ru(bipy) 2 6a]-(PF 6 ) 2 , henceforth referred to as 11a (Scheme 3a). Enantioenriched (Δ)-11a and (Λ)-11a were obtained by using chirally resolved precursors (Δ)-[Ru(bipy) 2 (py) 2 ]((S,S)dbt) and (Λ)-[Ru(bipy) 2 (py) 2 ]((R,R)-dbt) (dbt = O,O′dibenzoyl-tartrate) 30a,b in place of racemic Ru(bipy) 2 Cl 2 , followed by anion exchange with KPF 6 . Due to the presence of the asymmetric bipyridine 6a, complex 11a has C 1 symmetry. As a result, all the signals of the atoms are chemically inequivalent in the 1 H and [START_REF] Kaneko | Synthesis of Azahelicene N-Oxide by Palladium-Catalyzed Direct C-H Annulation of a Pendant (Z)-Bromovinyl Side Chain[END_REF] C NMR spectra (see the Supporting Information).

The structure of 11a was further confirmed by X-ray crystallography of a single crystal grown by slow diffusion of Et 2 O into a MeCN solution of (rac)-11a. It crystallized in the P1̅ centrosymmetric space group in which both enantiomers Δ and Λ are present (Figures 5a andS47). Remarkably, upon Scheme 3. Synthesis of (a) Racemic and Enantioenriched 11a and (b) Diastereomeric Mixture (P,Δ)/(M,Λ)-and (P,Λ)/ (M,Δ)-11c and of Diastereo-and Enantioenriched 11c a a The colors indicated correspond to those used in Figure 7. coordination with Ru(II), the bipy helicene 6a generates a fused metallic bis-helicenic system, one aza [4]helicene (displaying a helicity of 26.35°) and one ruthena [4]helicene (Ru[4]H in Figure 5c) with a helicity of 38.62°. This approach thus represents a simple yet powerful procedure to generate metal-based multihelicenic systems. Additionally, the fixed Λ configuration at the ruthenium center induces the M helix in the generated ruthena [4]helicene and the P-handed one in the fused aza [4]helicene (and vice versa), thus demonstrating control of the helical stereochemistry by the ruthenium in the solid. However, these [4]helicenic architectures are most probably fluxional in solution.

The reaction of (rac)-Ru(bipy) 2 Cl 2 with (rac)-6c in place of achiral 6a, followed by Cl -to PF 6

-metathesis, should give a diastereomeric mixture of the forms of 11c due to the presence of two stereogenic elements: helically chiral M/P helix and the Δ/Λ chirality at the metal (Scheme 3b). Indeed, the complicated 1 H NMR spectrum of 11c after purification by column chromatography was attributed to two sets of signals (see Figure S29). To our delight, a single crystal of the enantiomeric pair (M,Λ)/(P,Δ)-11c suitable for X-ray analysis was obtained by slow vapor diffusion of Et 2 O into a MeCN solution (Figures 6a andS48). A comparison of the NMR spectra of crystals and mother liquor revealed an almost perfect separation of the diastereomers and also enabled the assignment of some signals to the corresponding diastereomers (see Figures 7 andS29). By this comparison, it was found that (M,Λ)/(P,Δ)-11c was present in the originally formed mixture in a small excess of 59:41. It is notable that the coordination to Ru(II) provokes the formation of a ruthena [4]helicene (with a helicity of 44.35°) fused to the aza [6]helicene unit (of 54.82°h elicity) in which the (M,Λ) unit imposes the (M)-Ru [4]H helix, and vice versa, in the solid state. However, no conclusion can be drawn in the solution state where the ruthena [4]helicene unit is expected to be fluxional.

To obtain diastereo-and enantioenriched 11c, the reaction between (M)/(P)-6c and resolved (Δ)-[Ru(bipy) 2 (Py) 2 ]-((S,S)-dbt)/(Λ)-[Ru(bipy) 2 (Py) 2 ]((R,R)-dbt) precursors was conducted (see Scheme 3b). In all cases, the minor diastereomer was present in approximately 10% as revealed by 1 H NMR analysis (see Figure S34), suggesting that the reaction did not proceed with complete stereoselectivity in the sense of Δ/Λ isomerism.

Finally, the complexation of bis-bipyridine [7]helicene 10b to the Ru(II) precursor was studied (Scheme 4). The reaction of (rac)-10b with 2 equiv of (rac)-Ru(bipy) 2 Cl 2 provided two major products, which were separated by column chromatography. Both compounds were unambiguously identified by mass spectrometry as bis-ruthenium complex 12 and monoruthenium complex 13. In the case of 12, a single crystal of the (P,Λ,Λ)/(M,Δ,Δ)-enantiomeric pair was obtained by slow vapor diffusion of CHCl 3 into a MeCN solution of 12 (Figure 6c). Here again, in complex (P,Δ,Δ)-12, two fused Ru [4]H helicenes are formed. They display helicities of 26.60°a nd 33.62°but different (P) and (M) configurations within the same complex, thus showing no control of their chirality in the solid. In addition to (M,Δ,Δ)-and (P,Λ,Λ)-isomers, the diastereomeric mixture also contained the mixed C 1 symmetrical (Δ,Λ)-isomer (see Figure S35). For 13, a single crystal containing the (P,Λ)/(M,Δ)-enantiomeric pair was grown by slow vapor diffusion of Et 2 O into a MeCN solution of 13 (see Figure S50). Upon coordination, a fused Ru [4]H helicene displaying a 35.55°helicity is also formed with its (M) configuration controlled by the (P)-heptahelicene and vice versa, thus showing induction of chirality in the solid state.

Diastereo-and enantioenriched complexes 12 were synthesized by the reaction of (M)-or (P)-10b with either (Δ)-[Ru(bipy) 2 (Py) 2 ]((S,S)-dbt) or (Λ)-[Ru(bipy) 2 (Py) 2 ]((R,R)dbt) precursors (Scheme 4). Even though an excess of the ruthenium precursor was employed, the synthesis of the dinuclear complex 12 was always accompanied by the formation of a small amount of mono-Ru intermediate 13 (for details, see the Supporting Information). Both ruthenium ions in the enantioenriched forms of 12 have (Δ,Δ) or (Λ,Λ) configuration. As a result, all complexes possess an overall C 2 symmetry. In (P,Λ,Λ)/(M,Δ,Δ)-12, part of a terminal ring of The colors indicated correspond to those used in Figure 6.

the helical scaffold is strongly shielded by 2,2′-bipyridine placed in its vicinity. This is reflected in a significant change in the chemical shifts of 2-H (5.27 ppm) and 3-H (6.16 ppm), which are up to 1 ppm lower in comparison to the other enantiomeric pair (see Figure S35).

Absorption and Emission Properties of Complexes 11a, 11c, and 12. Complexes 11a, 11c, and 12 display broad and intense UV-vis absorption spectra (Figures 5 and6, bottom parts, and Figure 8) with very similar features, notably a strong absorption band around 290 nm and moderately intense ones around 250 and 350 nm, likely corresponding to π-π* transitions of the ligands. These bands are almost 1 order of magnitude stronger in the hexa-and heptahelicenic complexes 11c and 12 than in 11a. 18 They are accompanied by two bands of weaker intensities around 450 and 520 nm that are commonly assigned to MLCT-type transitions. Much of the intense interest in [Ru(bipy) 3 ] 2+ and its derivatives over the past 40 years has been driven by their attractive emission properties. [Ru(bipy) 3 ] 2+ is the archetypal 3 MLCT emitter. 18,31 The coordination as opposed to the organometallic nature of the bonding and the relative energies of the orbitals are such that the HOMO is primarily localized on the metal, and the LUMO on the ligand. The 1,3 MLCT energies can thus be rationalized and controlled according to the nature of the ligands, often showing good correlation with the oxidation and reduction potentials. 18a,32 In heteroleptic analogs, the LUMO is typically localized largely on the ligand(s) having the lowestenergy π* orbitals associated with it. Thus, where one bipy ligand is replaced by a more conjugated analogue, a reduction in the 3 MLCT and 1 MLCT energies can be anticipated; indeed, numerous such examples have shown the expected redshift in the emission and lowest-energy absorption bands, respectively, as a consequence. 18,31,[START_REF] Barigelletti | Influence of the Ligand Structure on the Electrochemical and Spectroscopic Properties of Ruthenium(II)-Polypyridine Complexes[END_REF] In the present series of heteroleptic complexes, such an effect is to be expected, since the extended conjugation of the helicene bipyridine ligand will serve to lower its π* orbitals. The effect is immediately clear in the absorption spectra (Figures 5b, 6b,d, and 8 and Table 2), where it can be seen that the lowest-energy absorption bands are centered around 510-520 nm in each case. These values contrast with that of around 455 nm for [Ru(bipy) 3 ] 2+ under the same conditions, indicating a stabilization of the 1 MLCT state of around 2500 cm -1 as a result of the more extended conjugation associated with the aza-aromatic. There is, however, little difference In deoxygenated acetonitrile at 295 ± 1 K and in butyronitrile at 77 K. b Values in brackets are for an air-equilibrated solution. c Values estimated assuming that the emitting triplet state is formed with unit efficiency upon excitation into the singlet bands, such that k r = Φ/τ and Σk nr = (1-Φ)/τ. d Bimolecular rate constants for quenching by O 2 , estimated on the basis of the lifetimes in a deoxygenated and air-equilibrated solution.

between 11c/12 and 11a, indicating that the additional aromatic rings incorporated within the helicene ligands of 11c/12, remote from the quinoline moiety, have little influence in further stabilizing the LUMO compared to the parent 11a.

All of the new complexes are found to be luminescent in solution at room temperature (Table 2). The emission and excitation spectra of (M,Δ)-11c and (P,Λ,Λ)-12 in MeCN at 295 K are shown in Figure 8, together with the emission spectra in PrCN at 77 K. Corresponding spectra of the other diastereomers of 11c and 12, and of the parent (rac)-11a, are given in Figures S54-S56. The onset of the emission is around 700 nm in each case, such that most of the luminescence falls in the NIR region of the spectrum with a maxima of around 790 nm (Table 2). This is a challenging part of the spectrum for detection, being at the edge of the range for conventional visible photomultiplier tubes yet somewhat too short for the wavelength of the NIR detectors. Optimal results were obtained using a back-illuminated deep-depletion CCD detector (the details of the instrumentation are given in the Supporting Information). As in absorption, there is a large redshift in the emission maxima relative to [Ru(bipy) 3 ] 2+ , reflecting the stabilization of the 3 MLCT associated with the more extended conjugation on the ligand. Again, there is little difference between the complexes 11c/12 and 11a. The emission maxima of around 780 nm compare with values of 700 and 742 nm for quinoline-containing complexes [Ru-(bipy) 2 (pq)] 2+ and [Ru(bipy) 2 (biq)] 2+ , which are perhaps the closest literature models (pq = 2-pyridylquinoline; biq = 2,2′biquinoline). 34a A complex featuring an azabenzannulated perylene diimide could be construed as a related example featuring the benzannulated phenanthridine moiety of the present complexes for which λ max em = 780 nm, though the nature of the excited state is quite different in that case. 34b The luminescence quantum yields are low, of the order of 0.1% (Table 2). Low values are to be anticipated, given the low energy of the excited state and the fact that the energy gap law typically applies well to metal bipyridine-based complexes. 34c However, the luminescence lifetimes of the helicene complexes remain quite long, of the order of a few hundred nanoseconds (Table 2), suggesting that the low quantum yields might be due in part to reduction in the radiative rate rather than to particularly severe nonradiative decay. Indeed, the estimation of the radiative and nonradiative rate constants, k r and Σk nr , indicates that the former is around an order of magnitude lower than for [Ru(bipy) 3 ] 2+ . Such an effect could be attributed to reduced metal character in the excited state with increasingly conjugated ligands 35a and/or to changes in the relative energies of higher singlet and triplet states that couple through spin-orbit coupling. 35b The emission is modestly quenched by dissolved molecular O 2 (as expected for lifetimes of this order of magnitude) with bimolecular rate constants of around 10 9 M -1 s -1 .

Although there is little difference between the spectra of the different diastereoisomers, it is intriguing to note a small but significant difference between the quantum yields and lifetimes of the diastereoisomers of 12. The emission of the (P,Λ,Λ)isomer is brighter and longer-lived than that of the (M,Λ,Λ), apparently due largely to an almost 4-fold difference in Σk nr . The difference most likely arises from the different conformation of the two complex units relative to one another, influencing the exposure to the solvent and hence the excitedstate deactivation pathways. [START_REF] Gauthier | Long-Lived Circularly Polarized Phosphorescence in Helicene-NHC Rhenium(I) Complexes: The Influence of Helicene, Halogen, and Stereochemistry on Emission Properties[END_REF] ECD Spectra of Complexes 11a, 11c, and 12. The ECD spectra of the enantioenriched forms of 11a in MeCN are mirror images of one another (Figure 5b). Enantiomer (Λ)-11a shows a positive band at 292 nm (Δε = +60 M -1 cm -1 ), a weak positive one at 245 nm (Δε = +24 M -1 cm -1 ), and two weak negative bands at 275 nm (Δε = -23 M -1 cm -1 ) and at 219 nm (Δε = -33 M -1 cm -1 ). Additionally, two negative ECD bands of very low intensities (Δε = -2 M -1 cm -1 ) are found at 375 and 510 nm, i.e., in the MLCT region. The absolute stereochemistry can be easily deduced from the starting enantioenriched Ru precursors and confirmed by comparison of the ECD fingerprints at 292 nm with known chiral complexes. [START_REF]Tartrate resolving agent: (a) Hua, X.; von Zelewsky, A. Enantiomerically Pure Chiral Ru II (L-L) 2 Building Blocks for Coordination Compounds[END_REF] The ECD spectra of diastereo-and enantioenriched 11c in MeCN are depicted and compared in Figure 6b. Both enantiomeric pairs (P,Λ)/(M,Δ)-and (P,Δ)/(M,Λ)-11c display mirror-image spectra. (P,Λ)-11c exhibits more intense ECD signals with a strong positive band at 291 nm (Δε = +120 M -1 cm -1 ) accompanied by a weaker positive band at 335 nm (Δε = +45 M -1 cm -1 ), a strong negative band at 251 nm (Δε = -135 M -1 cm -1 ), and weak bands at 523 nm (Δε = +8 M -1 cm -1 ), 451 nm (Δε = -11 M -1 cm -1 ), and 394 nm (Δε = +8 M -1 cm -1 ). (P,Δ)-11c exhibits two strong positive bands at 344 nm (Δε = +60 M -1 cm -1 ) and 275 nm (Δε = +70 M -1 cm -1 ), two strong negative bands at 294 nm (Δε = -70 M -1 cm -1 ) and 236 nm (Δε = -100 M -1 cm -1 ) and weak bands at 507 nm (Δε = +17 M -1 cm -1 ), 443 nm (Δε = -6 M -1 cm -1 ), and 314 nm (Δε = +22 M -1 cm -1 ). Overall, thanks to the presence of the hexahelix, the enantioenriched 11c derivatives display more intense ECD responses than the 11a ones.

The ECD spectra of diastereo-and enantioenriched 12 in MeCN are depicted and compared in Figure 6d. Both enantiomeric pairs (P,Λ,Λ)/(M,Δ,Δ)-and (P,Δ,Δ)/ (M,Λ,Λ)-12 display mirror-image spectra. Overall, the (P,Λ,Λ)-diastereomer shows less intense ECD signals with more crossing points than the (P,Δ,Δ) one. (P,Λ,Λ)-12 exhibits three strong bands at 277 nm (Δε = -150 M -1 cm -1 ), 291 nm (Δε = +105 M -1 cm -1 ), and 337 nm (Δε = +110 M -1 cm -1 ), accompanied by several weak bands at 306 nm (Δε = -23 M -1 cm -1 ), 435 nm (Δε = -24 M -1 cm -1 ), 507 nm (Δε = +16 M -1 cm -1 ), and 547 nm (Δε = -12 M -1 cm -1 ). (P,Δ,Δ)-12 displays one strong negative band at 294 nm (Δε = -295 M -1 cm -1 ), one moderate positive band at 367 nm (Δε = +115 M -1 cm -1 ), three weaker bands at 532 nm (Δε = +65 M -1 cm -1 ), 277 nm (Δε = +55 M -1 cm -1 ), and 266 nm (Δε = -50 M -1 cm -1 ), and one weak band at 446 nm (Δε = -10 M -1 cm -1 ). The heptahelicenic structure thus leads to a strong chiroptical response, which is further increased through a synergistic contribution of the two Ru centers. It is worth noting that mirror-imaged ECD spectra were systematically obtained for each enantiomeric pair of 11a, 11c, and 12, which confirms that the reactions proceeded without a loss of enantiopurity.

Spectroelectrochemical Properties of Complexes 11a, 11c, and 12. The electrochemical properties of complexes 11a, 11c, and (M,Δ,Δ)-and (M,Λ,Λ)-12 were studied by cyclic voltammetry recorded in MeCN under an inert atmosphere with 0.1 M Bu 4 NPF 6 as the supporting electrolyte. The half-wave redox potentials were determined from the average of the anodic and cathodic peak potentials for the reversible waves. The cyclic voltammograms depicted in Figure 9 reveal one reversible Ru(II)/Ru(III) oxidation wave at +1.14 and +1.23 vs SCE for complexes 11a and 11c, respectively. These values are very similar to those found in the literature for [Ru(bipy) 3 ] 2+ , 19a,37a while for the bis-Ru complex diastereomers (M,Δ,Δ)-and (M,Λ,Λ)-12, higher values were obtained (+1.31 and +1.26 V). Monoruthenium complexes 11a and 11c also display three reversible waves in reduction (-1.10, -1.60, and -1.86 V for 11a; -1.05, -1.51, and -1.75 V for 11c). These reduction potentials correspond to Ru(II)/ Ru(I), Ru(I)/Ru(0), and Ru(0)/Ru(-1) one electronreduction steps and are found to be similar to the reduction potentials of the [Ru(bipy) 3 ] 2+ systems. 19,23 The bisruthenium complexes (M,Δ,Δ)-and (M,Λ,Λ)-12 appear easier to reduce and exhibit the first set of two reversible waves (-1.11 and -1.08 V) corresponding to the two Ru(II)/Ru(I) processes of the Ru atoms that do not reduce at the same potential, thus evidencing an electronic interaction between the two metal centers via the π-helicene bridge. 37b,c,d Another two-electron reduction wave corresponding to the Ru(I)/ Ru(0) reduction of the two Ru centers is also found (-1.50 to -1.48 V).

Redox-Triggered Chiroptical Switching Activity. On the basis of these results, it appeared interesting to take advantage of the reversible oxidation and reduction processes and to study the electrochromic and chiroptical switching activity of such complexes. For this purpose, enantioenriched complexes (Λ)-11a, (P,Δ)-11c, and (P,Δ,Δ)-and (P,Λ,Λ)-12 were examined. The one-electron oxidation process was first studied by UV-vis and ECD spectroscopies in an optically transparent thin-layer electrochemical (OTTLE) cell (MeCN/ 0.2 M Bu 4 NPF 6 ) upon applying a potential up to ca. 1.3 V (Figure 10; see the electrochemical conditions in the Supporting Information). In all cases, several isosbestic points were observed in both UV-vis and ECD. Overall, the UV-vis spectra underwent a strong decrease of intensity of the high energy band around 290 nm. Oxidation was accompanied by a 15 nm red shift. In the higher energy domain, a disappearance or a decrease of the broad absorption bands located between 440 and 520 nm was observed. In the ECD spectra, the strong positive band around 300 nm in (Λ)-11a and (P,Δ)-11c underwent a significant decrease accompanied by a ca. 15 nm red shift, while the low-energy bands exhibited intensity decreases (see Figure 10a,b). Diastereomeric complexes (P,Δ,Δ)-and (P,Λ,Λ)-12 also evidenced similar changes (see Figure 10c,d). In contrast to the UV-vis spectra, the effects in ECD were different for the two diastereomers. The oxidation of (P,Λ,Λ)-12 resulted in an inversion of the positive band at 291 nm (Δε value moved from +105 to -70 M -1 cm -1 ); the broad positive band at 337 nm was split into two less intense bands, and the two weak bands between 480 and 600 nm vanished. Upon the oxidation of (P,Δ,Δ)-12, the bands at 294 and 367 nm were red-shifted around 24 and 10 nm, respectively, and bands at 266, 277, and 532 nm disappeared.

Since the comparison between the ECD spectra of (P,Λ,Λ)-12 in the Ru(II) and Ru(III) oxidation states shows dramatic changes in the chiroptical properties, the possibility of using such a system as a chiroptical switch was explored. For (P,Λ,Λ)-12, the difference between Δε values at 290 nm is not only significant (∼170 M -1 cm -1 ) but also accompanied by a change in sign. Therefore, it may be considered as a ± chiroptical switch. The reversibility of switching was further proved by several cycles of oxidation and reduction of (P,Λ,Λ)-12 in MeCN, which were accompanied by a modulation of the ECD signal upon applying potential steps between 0.8 and 1.3 V (Figure 11). The helicene-bipy-Ru complexes described here thus constitute a new class of helicene-based redox-triggered chiroptical switches. 38 Due to the presence of several simultaneous redox steps, the multiple electron reduction processes of (Λ)-11a, (P,Δ)-11c, and (P,Δ,Δ)-and (P,Λ,Λ)-12 resulted in less significant and less clear changes, as compared to the one-electron oxidation. The spectroelectrochemical reduction processes are thus more difficult to interpret (for selected spectra, see Figures S57 andS58).

■ CONCLUSIONS

In summary, we have shown that the photocyclization of aromatic imines is a suitable method for the preparation of helicenes decorated with one or two bipy-moieties. The formation of aza [6]-and aza [7]helicenes displaying one or two complexing bipy units was accessed for the first time by this methodology. These ligands were used for the preparation of chiral ruthenium(II) complexes in diastereo-and enantioenriched forms, which were subsequently characterized. The coordination of bipy-helicenes to the ruthenium ion generates fused metallic bis-or tris-helicenic systems. The stereochemistry of these compounds has been examined in detail through their X-ray crystallographic structures. Spectroelectrochemical UV-vis and ECD studies of the prepared complexes revealed their extensive redox-modulated chiroptical properties. Due to the strong reversible changes in the ECD spectra upon oxidation of the bis-ruthenium complex, the system may be considered as a redox-triggered chiroptical switch. The above-described complexes open up new possibilities in the search for other helicenes with switchable redox and optical properties and will be further studied in this regard.

■ ASSOCIATED CONTENT

* sı Supporting Information

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.inorgchem.1c01379.

General Information on the materials and methods used, synthetic procedures, chiral separations, and characterization data (NMR, X-ray, optical rotation values, spectroelectrochemical data, and additional spectral information) (PDF)

Accession Codes CCDC 2056689-2056691 and 2080927-2080930 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/ data_request/cif, or by emailing data_request@ccdc.cam.ac. uk, or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

Figure 1 .

 1 Figure1. Examples of helicenes containing 2,2′-bipyridine units that have been reported in the literature.

Figure 2 .

 2 Figure 2. Targeted helical ligands incorporating bipyridine-like units (top) and their corresponding heteroleptic Ru(II) complexes with the other coordination sites occupied by two 2,2′-bipyridines.

Scheme 1 .

 1 Scheme 1. Optimized Conditions for the Exclusive Synthesis of Model Compound 2

Figure 3 .

 3 Figure 3. Single crystal X-ray diffraction structures of (a) 6c and (b) 10b (H atoms have been omitted for clarity).

Figure 4 .

 4 Figure 4. (a) ECD (up) and UV-vis spectra (bottom) of (P)/(M)-6c, -10a, and -10b in MeCN (∼10 -4 M) at r.t. (b) Emission (bottom) and CPL (up) spectra of 6c, 10a, and 10b in MeCN (∼10 -5 M, λ ex = 360-365 nm) at r.t.

Figure 5 .

 5 Figure 5. Single crystal X-ray diffraction structures of (a) 11a and (c) selected views of the helicenic parts; PF 6 -anions and H atoms were omitted for the sake of clarity. (b) UV-vis (bottom) and ECD (up) spectra of (Δ)/(Λ)-11a in MeCN (∼10 -4 M) at r.t.

Figure 6 .

 6 Figure 6. Single crystal X-ray diffraction structures and selected views of (a) (M,Λ)-11c and (c) (P,Λ,Λ)-12. PF 6 -anions and H atoms were omitted for the sake of clarity. UV-vis (bottom) and ECD (up) spectra of (b) (P,Λ)/(M,Δ)/(P,Δ)/(M,Λ)-11c and (d) (P,Λ,Λ)/(M,Δ,Δ)/ (P,Δ,Δ)/(M,Λ,Λ)-12 in MeCN (∼10 -4 M) at r.t.

Figure 7 .

 7 Figure 7. Comparison of 1 H NMR spectra of (P,Δ)-and (P,Λ)-11c at 400 MHz in CD 3 CN at r.t. See numbering in Scheme 3b.

Scheme 4 .

 4 Scheme 4. Synthesis of Diastereo-and Enantioenriched Complexes 12, Either as Mixtures or as Pure Stereoisomers a

Figure 8 .

 8 Figure 8. Absorption spectra (black), emission spectra (red), and excitation spectra (green) in MeCN at 295 K and emission in PrCN at 77 K (blue) of (a) (M,Δ)-11c and (b) (P,Λ,Λ)-12. The corresponding spectra of other complexes are shown in Figures S54-S56.

Figure 9 .

 9 Figure 9. Cyclic voltammograms of 11a, 11c, and (M,Δ,Δ)-and (M,Λ,Λ)-12 in degassed MeCN (0.1 M Bu 4 NPF 6 ) plotted versus the saturated calomel electrode (SCE), measured using ferrocene as an internal standard.

Figure 10 .

 10 Figure 10. Spectroelectrochemical studies UV-vis (bottom) and ECD (top) studies of the oxidation processes of (a) (Λ)-11a, (b) (P,Δ)-11c, (c) (P,Λ,Λ)-12, and (d) (P,Δ,Δ)-12 (OTTLE cell, MeCN, 0.2 M Bu 4 NPF 6 ).

Table 1 .

 1 Screening of Reaction Conditions for the Synthesis of 6b composition of the reaction mixture after photolysis [%] a

	entry	additive, glassware	4b	5b	6b
	1	HBF 4 •Et 2 O (4 equiv), Pyrex	81	0	19
	2	Pyrex	2	96	2
	3	quartz	71	0	29
	4	Ti(OiPr) 4 (5 equiv), quartz	1	3	96

a 2 mg of starting material; 60 min of irradiation.

Table 2 .

 2 Luminescence Properties of the Ruthenium(II) Complexes

		Φ lum / 10 -2	τ/ns b	k r /10 3 s -1c	Σk nr / 10 6 s -1c	k Q	O2 /10 8
	788	0.03	46 [40]	6.5	22	17	742	1800

a emission at 77 K complex absorption λ max /nm (ε/M -1 cm -1 ) emission λ max /nm M -1 s -1d λ max /nm τ/ns (rac)-11a 289 (66 700), 337 (19 250), 405 (10 800), 437 (13 400), 510

(11 400)

■ ACKNOWLEDGMENTS

We thank the Centre National de la Recherche Scientifique (CNRS) and the University of Rennes. This work was supported by the Czech Science Foundation (grant no. 20-19353S). M.K. is grateful to the Ministry of Education, Youth and Sports of the Czech Republic and EU-European Structural and Investment FundsOperational Programme Research, Development, and Education for the project U ́CHP Mobilita II (CZ.02.2.69/0.0/0.0/18_053/0016920). R.R. thanks Xunta de Galicia for a Postdoctoral fellowship. The authors thank Sitthichok Kasemthaveechok from the University of Rennes 1 for help with the electrochemical measurements. NMR and ECD experiments were performed on the PRISM core Facility (Biogenouest, UMS Biosit, Université de Rennes 1).

Authors

Martin Kos

Author Contributions

M.K. performed the synthesis of the ligands and complexes. R.R. performed CD, CPL, and spectroelectochemical studies. N.V. performed HPLC separation of the ligands. I.C., M.C., E.C., and J. Syḱora performed analysis (X-ray and NMR). J.A.G.W. performed nonpolarized luminescence studies. V.C., J. Storch, and J.Z. designed the synthesis of helicenes and were involved in the supervision and revision and editing of the manuscript. J.C. designed the synthesis of the complexes and wrote/revised together with other authors the manuscript.

Notes

The authors declare no competing financial interest.


Thomas Nivet

Amandine Baptiste

Lisa Belin

Pascale Ghillani Dalbin

Caroline Algrin

Sylvain Choquet

Thierry Lamy

Véronique Morel

Lucile Musset

Damien Roos- Weil

Karine Viala

Véronique Leblond

Marine Baron
email: marine.baron@aphp.fr

Immunochemotherapy versus rituximab in anti-MAG neuropathy: a report of 64 patients

Keywords: main text 2999 words, Figures: 5, Tables: 3

Monoclonal immunoglobulin M (IgM) anti-myelin-associated glycoprotein (MAG) neuropathy is a rare disabling condition, most commonly treated with rituximab monotherapy (R), which leads to neurological improvement in only 30%-50% of patients. The combination of rituximab plus chemotherapy has been proven to improve the level of responses. We studied the outcomes of anti-MAG neuropathy patients treated either by R, or by immunochemotherapy (ICT) in our centre, focusing on the incidence of the first neurological response evaluated by the modified Rankin Scale (mRS). From 2011 to 2018, 64 patients were studied: 34 were treated with R and 30 with ICT. According to our treatment decisionmaking process, the median mRS was higher in the ICT group (mRS 2) compared to the R group (mRS 1). At 1 year, mRS improvement rates were 46% and 18% of the ICT and R groups of patients respectively, with a median time to response of 8 and 13 months (p=0.023).

Adverse effects were higher in the ICT group: 62% vs 15% (p˂0.01) all grades included. One secondary acute leukaemia occurred 5 years after treatment by ICT. In conclusion, ICT may be used as a valid option for patients with rapidly progressive and/or severe anti-MAG neuropathy symptoms.

INTRODUCTION

Monoclonal gammopathy of clinical significance (MGCS) is defined by the presence in the serum of monoclonal immunoglobulin (Ig) or monoclonal free light chain produced by indolent B-cell clones in the absence of overt tumour proliferation but responsible for organ damage because of toxicity of the monoclonal component.(1) Mechanisms of toxicity include deposition of all or part of the monoclonal Ig, immune complex formation, complement activation or autoantibody activity against a tissue antigen. Any antibody activity against myelin-associated glycoprotein (MAG) may be responsible for IgM anti-MAG antibodyrelated peripheral neuropathy which is a rare, disabling condition. Most frequently, there is no overt lymphoproliferative syndrome but monoclonal gammopathy of undetermined significance (MGUS) occurs. However, in 33% of cases, Waldenström macroglobulinemia (WM) or indolent B-cell lymphoma is present. [START_REF] Svahn | Anti-MAG antibodies in 202 patients: clinicopathological and therapeutic features[END_REF] The ensuing neuropathy is characterized by mostly sensitive disorders and is generally slowly progressive but there is great heterogeneity of clinical presentation among patients, and progression can lead to irreversible secondary axonal loss with disabling neurological outcomes. Rarely, acute worsening can occur and lead to major and rapid disability. [START_REF] Baron | Plasma exchanges for severe acute neurological deterioration in patients with IgM anti-myelin-associated glycoprotein (anti-MAG) neuropathy[END_REF]. It is estimated that 20%-45% of patients are disabled by severe progressive neuropathies that undermine their quality of life. [START_REF] Svahn | Anti-MAG antibodies in 202 patients: clinicopathological and therapeutic features[END_REF][START_REF] Nobile-Orazio | Long-term prognosis of neuropathy associated with anti-MAG IgM M-proteins and its relationship to immune therapies[END_REF] Thus, there is a need to develop effective treatments. The criteria required to initiate treatment are difficult to establish in anti-MAG neuropathy because of its rarity, its heterogeneous progressive course, the subjectivity of symptom presentations and the non-standardized evaluation criteria. [START_REF] Lunn | Immunotherapy for IgM anti-myelin-associated glycoprotein paraprotein-associated peripheral neuropathies[END_REF][START_REF] Pruppers | Recent advances in outcome measures in IgM-anti-MAG+ neuropathies[END_REF] Usually, treatment is warranted in case of significant disability and should not be based on IgM and/or anti-MAG levels. There are no clearly established therapeutic recommendations and there is insufficient evidence from most pilot studies to recommend any particular treatment. Rituximab monotherapy use is more and more frequent although its effectiveness has not been demonstrated by all groups. (5,7-9) Clinical scales improvement with rituximab monotherapy is reported in 30% to 50% of cases with a median delay of improvement ranging from 9 to 12 months. [START_REF] Dalakas | Advances in the diagnosis, immunopathogenesis and therapies of IgM-anti-MAG antibody-mediated neuropathies[END_REF] In WM and other lymphoproliferative disorders, immunochemotherapy (ICT) yields better outcomes than rituximab monotherapy [START_REF] Dimopoulos | Primary Treatment of Waldenström Macroglobulinemia With Dexamethasone, Rituximab, and Cyclophosphamide[END_REF]. In the context of MGCS, the treatment decision is based on the benefit-to-risk approach and frequently involves chemotherapy.(1) Indeed, rituximab may be combined with chemotherapy to target the underlying B-cell clone responsible for the production of anti-MAG antibodies and has been reported by several teams. [START_REF] Colchester | Chemoimmunotherapy with rituximab, cyclophosphamide and prednisolone in IgM paraproteinaemic neuropathy: evidence of sustained improvement in electrophysiological, serological and functional outcomes[END_REF][START_REF] Gomez | Anti Myelin-Associated-Glycoprotein Antibody Peripheral Neuropathy Response to Combination Chemoimmunotherapy With Bendamustine/Rituximab in a Patient With Biclonal IgM κ and IgM λ: Case Report and Review of the Literature[END_REF][START_REF] Gruson | Long-term response to rituximab and fludarabine combination in IgM anti-myelin-associated glycoprotein neuropathy[END_REF][START_REF] Massa | Bendamustinerituximab (BR) combined therapy for treatment of immuno-mediated neuropathies associated with hematologic malignancy[END_REF]. Our centre has shown that the addition of chemotherapy makes it possible to obtain a faster clinical response, the median time to response being 5 months in the ICT group compared to 9.5 months in the rituximab group. [START_REF] Hospital | Immunotherapybased regimen in anti-MAG neuropathy: results in 45 patients[END_REF] It is suggested that ICT may be preferred in case of rapid and/or severe neurological symptoms.

Based on these findings, we investigated whether patients with anti-MAG neuropathy would benefit from more intensive treatments. Here, we report the outcomes of a retrospective series of patients treated with rituximab (R) or rituximab plus chemotherapy at a single centre.

MATERIALS AND METHODS

Patients

Recruitment was conducted retrospectively based on medical records. The inclusion criteria were patients with anti-MAG neuropathy treated with R alone or in combination with chemotherapy. The diagnosis was related to the association of demyelinating neuropathy based on EMG features, clinical data matching and monoclonal gammopathy of the IgM type with anti-MAG activity. Clinical evaluation was assessed with the modified Rankin Scale (mRS; Table 1). IgM levels were assessed with protein electrophoresis and anti-MAG antibodies with ELISA (Bühlmann, Switzerland) using coated human MAG and peroxidaseconjugated anti-human IgM. Samples ≥ 5,000 BTU were considered as positive. Clinical data were obtained in accordance with the declaration of Helsinki and with ethical approval from national (CNIL 2212382) and local (CPP Ile-De-France 05/21/2014) ethics committees. All patients were informed and oral non opposition of each patient was recorded in medical files according with the ethical French law. Sixteen patients have been previously described with shorter follow-up. ( 16)

Treatments

The treatment decision was made according to the patient's symptoms, the impact on daily life and the natural course of the disease, independently of bone marrow evaluation. ICT was used to treat the patients with high mRS (3-4) and/ or acute or sub-acute (≤ 6 months) neurological worsening of the disease, subject to the age and the general status. Patients treated with ICT received 6 cycles of: dexamethasone (20 mg day 1) plus R (375 mg/m 2 day 1) plus oral cyclophosphamide (300 mg/m 2 day 1 to 5) (DRC), or oral fludarabine (40 mg/m 2 day 1 to 3) plus oral cyclophosphamide (250 mg/m 2 day 1 to 3) plus R (375 mg/m 2 day 1) (FCR), or oral fludarabine (40 mg/m 2 day 1 to 5) plus R (375 mg/m 2 day 1) (FR), or bendamustine (90 mg/m 2 day 1 and 2) plus R (375 mg/m 2 day1) (BR). In the R group, R was given: 375 mg/m 2 intravenous every week for 4 weeks.

Outcomes

The study's primary endpoint was the incidence of the first mRS improvement. Improvement was defined as mRS decrease ≥1, stabilization as stable mRS, and progression as mRS increase ≥1. The secondary endpoint was the survival without initiation of a new treatment defined as the time from the start of treatment and initiation of a new treatment or death. We also evaluated the electrophysiological change (improvement, stability, worsening), according to Lunn and Nobile-Orazio, [START_REF] Lunn | Immunotherapy for IgM anti-myelin-associated glycoprotein paraprotein-associated peripheral neuropathies[END_REF] the anti-MAG change (decrease defined as ≥ 25% titre decrease, increase defined as ≥ 25% titre increase, stability otherwise) and the IgM change (decrease defined as ≥ 25% level decrease, increase defined as ≥ 25% level increase, stability otherwise).

Statistical analysis

Characteristics of the study population were described in terms of frequencies for qualitative variables or medians and associated ranges for quantitative variables. Qualitative variables were compared using Chi-2 test (or Fisher exact test if appropriate ), quantitative variables were compared using Student test (or non-parametric Wilcoxon test in case of non-normal distribution). The cutoff date for the analysis was 20/01/2020. Median follow-up was estimated using reverse Kaplan-Meier. [START_REF] Schemper | A note on quantifying follow-up in studies of failure time[END_REF] Time to modified Rankin Score (mRS) improvement was defined as the delay between the start of treatment and the date of event. Patient alive without improvement of modified Rankin Score were censored at the date of their last known contact or death. Patient who died before an improvement of modified Rankin score were censored at the date of death. Survival analyses were performed using the Kaplan-Meier estimate. Incidence of the event was estimated using the following transformation F(t)= 1-S(t) where S(t) is the Kaplan-Meier estimate of survival functions.

Hazard ratios and their associated 95% confidence intervals were calculated using the Cox proportional hazard model. For multivariate analysis, we chose to adjust treatment effect on main confounding factors based on clinical knowledge: mRS at baseline evaluation and speed of worsening (fast/progressive) assessed before treatment initiation. The proportional hazards hypothesis was tested for each factor, with Schoenfeld's residuals test and plotting. All tests were two-sided and used a significance threshold at 5%. Analyses were performed with the R software, version 3.6.3 (R Development Core Team, 2011).

RESULTS

Patients and treatment

From 2011 to 2018, 78 patients with a positive anti-MAG dosage were treated with R or ICT.

Fourteen patients were excluded because of other concomitant indications of treatment (cryoglobulinemia, CANOMAD syndrome, active WM: n = 4) or lack of data (n = 10). Thus, 64 patients with anti-MAG neuropathy are reported here. Patient characteristics before treatment are summarized in Table 2. The median age at symptom onset was 63 years [IQR 55-69] and 55% of the patients were male. The median time between onset of neuropathy and treatment initiation was 4.3 years [IQR, [START_REF] Svahn | Anti-MAG antibodies in 202 patients: clinicopathological and therapeutic features[END_REF][START_REF] Baron | Plasma exchanges for severe acute neurological deterioration in patients with IgM anti-myelin-associated glycoprotein (anti-MAG) neuropathy[END_REF][START_REF] Nobile-Orazio | Long-term prognosis of neuropathy associated with anti-MAG IgM M-proteins and its relationship to immune therapies[END_REF][START_REF] Lunn | Immunotherapy for IgM anti-myelin-associated glycoprotein paraprotein-associated peripheral neuropathies[END_REF][START_REF] Pruppers | Recent advances in outcome measures in IgM-anti-MAG+ neuropathies[END_REF][START_REF] Dalakas | Placebocontrolled trial of rituximab in IgM anti-myelin-associated glycoprotein antibody demyelinating neuropathy[END_REF].The most common symptoms were: sensory deficit (83%), paraesthesia and dysesthesia (70%) and ataxia (67%). Distal lower limbs motor deficit was reported for 25 patients (39%), neurological pain for 33 patients (52%) and tremor for 11 patients (18%).. The most frequent type of onset was chronic (˃6 months) (81%) but 2 patients had acute progression (≤ 1 month).. The median mRS was 2 [IQR 1-2] in the overall population, and twelve patients (40%) of the ICT group had mRS of 3 or 4 versus 2 (6%) of the R group. The median monoclonal peak (for patients with measurable IgM peak, n = 43) and MAG antibody level (for n = 33 patients with anti-MAG dosage˂70,000 BTU) were, respectively, 4 g/L [IQR 3-4] and 32,900 BTU [IQR 23,400-43,000]. Thirty-one patients had anti-MAG antibody levels ˃70,000 BTU. The kappa isotype was predominant in 81% of patients. There was no evidence of an overt haematological malignancy in 30/53 patients (57%) with available bone marrow evaluation. Among the other patients, 18 had WM and 5 patients had non-WM lymphoplasmacytic lymphoma. Thirty-four patients were treated with R and thirty with ICT, including 13 (43%) with DRC, 13 (43%) with FR, 3 (10%) with FCR and 1 (3%) with BR.

Modified Rankin Scale outcome and time to new treatment

The median follow-up was 5 years [IQR 3.9-6.4] for the whole cohort and was longer for the ICT group (6.6 years) than for the R group (4 years). The incidence of the first mRS improvement was statistically different between the ICT group and the R group (HR = 2.41 CI95% [1.10, 5.28], p = 0.023). Twelve months after treatment initiation, 46% (CI95% [26; 62]) of patients had mRS improvement in the ICT group versus 18% (CI95% [2; 26]) in the R group (Fig. 1). In addition, the mean change of mRS between start of treatment and 12 months was 0.64 in the ICT group versus 0.15 in the R group (p = 0.036) (Fig. 2). At 3 years, 57% (CI95% [35; 72]) of patients had mRS improvement in the ICT group vs 30% (CI95% [11; 45]) in the R group. Median time to first mRS improvement was 25.2 months (CI95% [8.4; NR]) in the ICT group but it was not reached in the R group as less than 50% of patient had a mRS improvement. For responder patients, the median time to first response was 8 months [IQR 610] in the ICT group versus 13 months [IQR 929] in the R group. After adjustment on baseline mRS score and the type of onset, incidence of the first mRs improvement was no longer significant between ICT and R groups (HR = 1.34, CI95%[0.58 ; 3.12]).

At 5 years, 36% (CI95% [11; 45]) of ICT group patients have started a new line of treatment or died versus 39% (CI95% [12; 57]) of R group patients (p=0.675) (Fig. 3). Of note, 5 patients, all in the ICT group, continued to decrease their mRS after the first response. The mRS profile of each patient over time is reported in Fig. 4.

Other outcomes

Twelve months after treatment initiation, electrophysiological improvement occurred in 22/52 patients (42%) and its rate was higher in the ICT group (65%) vs the R group (24%) (p = 0.007). The electrophysiological improvement was concordant with the clinical mRS improvement in 88% of cases (Fig. 5A). Finally, decreases in anti-MAG and IgM were observed respectively in 27/39 (69%) and 19/48 (40%) patients, and we did not observe any statistical association between biological and mRS responses (Fig. 5B-C). Indeed, mRS improvement occurred in only 41% of patients with IgM decrease and in 32% of patients with anti-MAG decrease.

Tolerance

The ICT regimen was associated with higher adverse events including all grades: 62% in the ICT group versus 15% in the R group (p˂0.01), but no toxic death was reported (Table 3).

Rituximab-related infusion reactions were all classified as grade 12 and occurred in 6% of the patients. Grade 34 cytopenia and nausea/vomiting occurred, respectively, in 5 and 1 patients, all in the ICT group. Infectious complications were reported in 4 patients in the ICT group versus 1in the R group. They included 3 bacterial infections 1 septic shock, 1 febrile neutropenia and 1 parvovirus B19 infection (1 patient experienced 2 different infectious adverse events). Notably, 1 patient in the R group developed, after the fourth R injection, a grade 4 non-viral cytolytic hepatitis associated with neurological flare. Modified RS increased from 1 to 4 and the patient temporarily required a wheelchair. In parallel, EMG and anti-MAG antibody assays worsened. The patient gradually recovered his baseline clinical condition 9 months later. Finally, 1 patient in the ICT group died from secondary acute leukaemia diagnosed 5 years after treatment (DRC and then FR).

DISCUSSION

Here, we report the outcomes of the largest cohort of anti-MAG neuropathy patients treated with ICT or R monotherapy. As expected, clinical characteristics assessed with mRS were different in the 2 treatment groups as follows: patients in the ICT group were more disabled than those in the R group. Indeed, in our centre, patients with severe or rapidly progressive neuropathy are more prone to be treated with ICT as a result of our previous experiences. [START_REF] Hospital | Immunotherapybased regimen in anti-MAG neuropathy: results in 45 patients[END_REF] We assume that there is a major bias when comparing the efficacy of 2 treatment types but it reflects the heterogeneous presentation of the disease and the complexity of randomized trials in rare patient populations. Nevertheless, the time between onset of neuropathy and treatment initiation was similar between the 2 groups. In our cohort, the response rate at 1 year was higher (46% vs 18%) and the time to response (8 vs 13 months) shorter in the ICT group compared to the R group. In case of rapid neurological worsening with severe symptoms, a fast response is of great interest because, while waiting for the treatment to take effect, patients continue to become disabled, and the consequences may be irreversible. In the case of very slow disease progression, the patients may develop secondary axonal changes with loss of neurons. As a result, they are less likely to respond than patients with more recent disease, suggesting that, as previously noted by other authors, (19-21) a well-tolerated treatment such as R monotherapy may be proposed earlier during the disease progression in this slow context. Of note, ICT benefit was no longer significant in multivariate analysis. Taking into account confusion factors is useful in retrospective analysis. In rare patients population where randomized trials are not possible, estimating an hazard ratio at 1.34 may be clinically interesting without having the necessary power to be significant in the study. However, we cannot exclude that the effect of ICT vs. R is inferior due to residual confusion.

One way to improve treatment efficacy without adding adverse effects may be the use of new drugs targeting B cells, such as Bruton Tyrosine Kinase inhibitor (BTKi), but very few data are available in the specific context of anti-MAG neuropathy. In the study by Treon et al.,[START_REF] Léger | Placebo-controlled trial of rituximab in IgM anti-myelin-associated glycoprotein neuropathy[END_REF] patients received ibrutinib for progressive neuropathy, 3 of whom had anti-MAG antibodies. [START_REF] Treon | Ibrutinib in Previously Treated Waldenström's Macroglobulinemia[END_REF] Subjective improvement occurred in 5 patients and 4 remained stable. In a subsequent study, 4 patients with neuropathy were treated with ibrutinib: 2 had subjective improvement and 2 remained stable. ( 23) More recently, ibrutinib demonstrated objective improvement occurring early in the first 3 months in 3 patients with anti-MAG neuropathy. [START_REF] Castellani | The Bruton tyrosine kinase inhibitor ibrutinib improves anti-MAG antibody polyneuropathy[END_REF] These results suggest that BTKi should be considered for anti-MAG neuropathy patients in future clinical trials and that the delay of improvement may be short.

One concern with anti-MAG neuropathy is that international consensus on assessing response to treatment is still lacking and clinical evaluation is difficult because of inadequate scores.

Rankin and ONLS scores are disability scales and cannot effectively capture small functional changes that can greatly impact quality of life. The only-well defined sensory score available in clinical trials is the INCAT sensory score, but it is insufficiently sensitive to detect the small functional changes or sensory improvement concerning paraesthesia or pain for example. [START_REF] Draak | Comparing the NIS vs. MRC and INCAT sensory scale through Rasch analyses[END_REF][START_REF] Merkies | Inflammatory Neuropathy Cause and Treatment (INCAT) group. Clinimetric evaluation of a new overall disability scale in immune mediated polyneuropathies[END_REF]. Also, it highlighted that we probably underestimated the clinical impact of treatment because of lack of sensitivity of the neurological score and that we need to develop more sensitive scores. On the biological side, disease markers may not be suitable for assessing treatment efficacy. Indeed, we confirmed that anti-MAG antibody evolution was not correlated to the clinical response. (27,28) A possible explanation for this observation is that differences in the anti-MAG antibody titre are no longer detectable above a certain threshold.

We cannot detect changes in patients with anti-MAG titres ≥70,000 BTU at baseline. Moreover, the plasma anti-MAG antibody titre does not reflect its binding capacity in the nerve tissue and does not inform on its affinity. This is why anti-MAG antibody titre is of crucial interest for demyelinating neuropathy diagnosis but not for treatment evaluation.

Similarly, we did not find a correlation between the IgM response and the clinical response.

This may be explained in part by the low level of IgM monoclonal gammopathy that do not allow a correct assessment of peak reduction after treatment.

Finally, different treatment options were used according to the successive WM international guidelines. Purine-analogs based regimens were frequently used at the beginning of the twenties but are less used because of the risk of long-lasting cytopenia and myelodysplasia.

(29) DRC is effective, well tolerated and is one of the most used treatment option. [START_REF] Dimopoulos | Primary Treatment of Waldenström Macroglobulinemia With Dexamethasone, Rituximab, and Cyclophosphamide[END_REF][START_REF] Kastritis | Dexamethasone, rituximab, and cyclophosphamide as primary treatment of Waldenström macroglobulinemia: final analysis of a phase 2 study[END_REF] More recently, bendamustine plus rituximab have demonstrated a superior overall responses and progression-free survival with superior time to best response compared to DRC and BDR (bortezomib plus dexamethasone plus rituximab). [START_REF] Abeykoon | Assessment of fixedduration therapies for treatment-naïve Waldenström macroglobulinemia[END_REF][START_REF] Paludo | Bendamustine and rituximab (BR) versus dexamethasone, rituximab, and cyclophosphamide (DRC) in patients with Waldenström macroglobulinemia[END_REF] Thus, we recommend the use of alkylating based regimen in aggressive anti MAG neuropathy: BR in fit patients, and DRC in less fit or unfit patients .

In conclusion, our data suggest that treatment of anti-MAG neuropathy patients can be adapted to the heterogeneous clinical presentations and that ICT can be used to treat severe or rapidly progressive neurological symptoms in order to obtain a higher response rate with a shorter time to response.

TABLES

Figure 1 .

 1 Figure 1. Incidence functions of mRS response. Modified RS response was defined as a decrease ≥ 1 point under treatment. Purple line denotes patients treated with immunochemotherapy (ICT), green line denotes patients treated with rituximab alone (R).

Figure 2 .

 2 Figure 2. Mean modified Rankin Scale at baseline and 12 months after treatment initiation. Red lines denote mRS mean, bold lines denote mRS median.Figure 3. Probability of survival without a new treatment was started. Purple line denotes patients treated with immunochemotherapy (ICT), green line denotes patients treated with rituximab alone (R).

Figure 4 .

 4 Figure 4. Modified Rankin Scale profile of each patient under and after treatment. A. Immunochemotherapy (ICT) group, B. Rituximab (R) group. Vertical blue (for R group) and red (for ICT group) dotted lines denote the time point of 12 months after treatment initiation.

Figure 5 .

 5 Figure 5. Concordance between mRS response and other outcomes. A. EMG change, B. Anti-MAG change, C. IgM change. The EMG change was reported according to Lunn andNobile-Orazio (5) (improvement, stability or worsening). The anti-MAG change was defined as a decrease in case of ≥ 25% titer decrease, an increase in case of ≥25% titer increase and a stability in the other cases. The IgM change was defined as a decrease in case of ≥ 25% level decrease, an increase in case of ≥ 25% level increase and a stability in the other cases. The x axis denotes the neurological responder patients according to mRS improvement (yes) or not (no). The y axis denotes the frequency of improvement or increase (yellow color), stability (orange color) and worsening or increase (red color) according to the other parameters.

Table 1 . Modified Rankin Scale.

 1

	Scale	Symptoms
	0	No symptoms at all
	1	No significant disability despite symptoms; able to carry out all usual duties and
		activities
	2	Slight disability; unable to carry out all previous activities, but able to look after
		own affairs without assistance
	3	Moderate disability; requiring some help, but able to walk without assistance
	4	Moderately severe disability; unable to walk and attend to bodily needs without
		assistance
	5	Severe disability; bedridden, incontinent and requiring constant nursing care
		and attention
	6	Death

Table 2 . Baseline clinical and biological characteristics of the patients before treatment.

 2 Abbreviations. ICT, immunochemotherapy; NS: not suitable.

	Characteristic			Total	ICT	Rituximab	P value
	No. of patients		64	30	34
	Median age [IQR]		63 [55-69]	63 [57-72]	62 [54-68]	0.641
	Gender, n. (%)		Male: 35 (55)	Male: 19 (63)	Male: 16 (47)	0.192
				Female: 29 (45)	Female: 11 (37)	Female: 18 (53)
	Underlying hematological				0.131
	malignancy* (n=53), n. (%)
	-IgM MGCS		30 (57)	17 (63)	13 (50)
	-WM			18 (34)	6 (22)	12 (46)
	-Other			5 (9)	4 (15)	1 (4)
	lymphoproliferative disorder
	Clinical presentation, n. (%)
	-Sensory deficit		53 (83)	27 (90)	26 (77)	0.152
	-Paresthesia/ dysesthesia	45 (70)	15 (50)	30 (88)	0.001
	-Ataxia			43 (67)	26 (87)	17 (50)	0.002
	-Pain			33 (52)	12 (40)	21 (62)	0.082
	-Motor deficit		25 (39)	19 (63)	6 (18)	˂0.001
	Median	time	between	4.3 [2.1-7.4]	4.2 [1.8-7.2]	4.8 [2.4-9.5]	0.1563
	neuropathy onset and treatment
	initiation, years [IQR]
	Type of onset, n. (%)					0.005
	-Acute/ Sub-acute		12 (19)	10 (33)	2 (6)
	-Chronic			52 (81)	20 (67)	32 (94)
	Modified Rankin Scale					0.001
	-Median [IQR]		2 [1-2]	2 [2-3]	1 [1-2]
	-mRS 1-2 (%)		50 (78)	18 (60)	32 (94)
	-mRS 3-4 (%)		14 (22)	12 (40)	2 (6)
	Spike IgM level, g/L [IQR]	4 [3-4]	6 [5-8]	4 [3-8]	˂0.001
	Kappa isotype, n. (%)		51 (81)	25 (83)	26 (79)	0.202
	Anti-MAG titer
	-˃70,000 BTU, n (%)		31(48)	16 (53)	15 (44)	0,462

Acknowledgments

. This study was supported by grants from INCA-DGOS-Inserm_12560 (SiRIC CURAMUS is financially supported by the French National Cancer Institute, the French Ministry of Solidarity and Health and Inserm with financial support from ITMO Cancer AVIESAN).

Funding statement. No funding. Authorship statement. V.L. and M.B designed the research study, T.N., C.A., S.C., T.L., V.M., K.V., D.R-W., V.L. and M.B. took care of the patients. P.G-D. and L.M. performed immunochemistry analysis, T.N. collected data, A.B. and L.B. performed statistical analysis, T.N., M.B., L.B., D.R-W. and V.L. wrote the manuscript, all authors reviewed the manuscript.