Thomas Castanheiro

Mihaela Gulea

Morgan Donnard

Jean Suffert

Keywords: thiocyanate, copper, aerobic oxidative coupling, disulfide, cyanation

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Practical access to aromatic thiocyanates by CuCN-mediated direct aerobic oxidative cyanation of thiophenols and diaryl disulfides.

Thomas Castanheiro, Mihaela Gulea,* Morgan Donnard* and Jean Suffert* [a] Dedicated to Pr Alexandre Alexakis on the occasion of his retirement Abstract: We report a practical and mild aerobic oxidative CuCNmediated cyanation of thiophenols and diaryl disulfides. The reaction is performed under air at room temperature and reaches aromatic thiocyanates in moderate to good yields starting from a broad range of diversely functionalized substrates.

Organic thiocyanates are important synthetic intermediates for the preparation of various sulfur-containing compounds, such as thiols, sulfides, disulfides, thioesters, thiocarbamates, and sulfur heterocycles, and are also constituents of biologically active compounds. 1 Compared to alkyl thiocyanates, which are generally easily avail-able from alkyl halides and potassium or ammonium thiocyanate, aryl thiocyanates are more difficult to access. Besides the synthetic applications mentioned above, aryl thiocyanates have been used as reagents for the cyanothiolation of alkynes. 2 Two main strategies are currently used to prepare these compounds: the first one (path 1, Scheme 1) consists in the reaction of various non-sulfur aromatic substrates (arenes or aryl metal, aryl halides, aryl diazonium salts, or arylboronic acids) with a thiocyanating agent such as a thiocyanate salt or thiocyanogen. 3 The second one (path 2, Scheme 1) is based on the nucleophilic attack of a cyanide (KCN, NaCN, or TMSCN) on a substrate bearing an electrophilic sulfur (aryl disulfides, aryl sulfenyl or sulfonyl derivatives). 4 All these procedures require high temperatures or the presence of a metal catalyst, and the main drawback of the second strategy represents the use of highly toxic and moisture-sensitive cyanation agents. An additional approach making use of electrophilic CN sources has been developed but is infrequently used. 5 Although CuCN was already used as the cyanide source for the formation of a C-CN bond [START_REF] Rosenmund | For selected papers[END_REF] and very recently for a N-CN bond, 7 no example of sulfur cyanation by this reagent was described to date. Scheme 1. Methods for the synthesis of aryl thiocyanates Herein, we report an efficient S-cyanation of aromatic thiols and disulfides by CuCN, at room temperature and using oxygen as oxidant [START_REF] Lam | coppermediated oxidative coupling: a)[END_REF] (Scheme 1).

Preliminary studies were conducted on thiophenol 1a as a model substrate. Acetonitrile was chosen as solvent and molecular oxygen (air) as oxidant for obvious practical reasons. In first place we controlled if a ligand was required and no reaction was observed in the absence of it (Table 1, entry 1). Then the influence of the copper ligand was evaluated (Table 1, entries 2-7). Different usual ligands have been screened and it appeared that only two of them allowed the cyanation to take place, namely N-methylimidazole and N,N'tetramethylethylenediamine (Table 1, entries 6 and7). TMEDA turned out to be the best ligand as the reaction was complete after 18h and thiocyanate 3a was obtained in a good 94% yield whereas N-methylimidazole drove only to a poor 25% yield of the targeted compound along with a large amount of diphenyl disulfide 2a. Ligands such as triphenylphosphine, acetylacetone, pyridine or 1,10-phenantroline were unable to promote the reaction and only disulfide 2a, product of thiophenol oxidation, was recovered after 18h reaction.

Table 1. Screening of ligands for the copper-mediated oxidative cyanation of thiophenol.

Entry

Ligand Conv (%) [a] Ratio 2a:3a [a] Yield 3a (%) [b] 1 Interestingly, it appeared that the full conversion of thiol 1a into disulfide 2a was almost instantaneous, presumably catalyzed by copper salts, and we envisioned that the reaction could be performed on the disulfide itself with an equivalent efficiency. It has been confirmed by the transformation of diphenyl disulfide 2a into thiocyanate 3a in a similar yield (88%) as the reaction performed on thiophenol. Remarkably, we noticed that the use of sodium thiolate salts as substrate considerably accelerated the reaction. For example, sodium phenylthiolate was converted into thiocyanate 2a after 1h in comparable yield (92%). The effect of the solvent on the cyanation of diphenyl disulfide has been then investigated (Figure 1) and has been shown to be dramatic. Toluene, methanol, and 1,4-dioxane appeared incompatible with the reaction while N,N-dimethylformamide, tetrahydrofuran, and dichloromethane allowed the reaction to take place but drove after 18h to the targeted thiocyanate 3a in modest yields (respectively 36%, 41% and 51%). With the optimized conditions in hand, we investigated the scope of the reaction by performing the copper-mediated cyanation on representative aromatic thiols and diaryl disulfides (Scheme 2). Complete consumption of the disulfides was controlled after 18h by GC/MS or TLC.

Methyl-substituted substrates such as p-tolylthiocyanate 3b and 2,4-dimethylthiocyanate 3c were synthesized in good yields of 74% and 71%. Diversely chlorinated or fluorinated disulfides (2d, 2e, and 2f) furnished the desired thiocyanate in yields up to 95% (4-fluorophenyl thiocyanate 3e) while brominated ones (2g and 1h) appeared less reactive, probably for electronic reasons, and drove to corresponding thiocyanates (3g and 3h) in 40-50% yields. Electron-withdrawing substituents such as nitro group lower the reactivity of the disulfide, so disadvantaging the formation of the desired product. Thus, thiol 1i was cyanated into 3i in a poor 13% yield after 18h at 80°C while only disulfide 2i was recovered when the reaction was performed at room temperature. Amide substituent appeared compatible with the transformation as thiol 1l was converted into thiocyanate 3l in reasonable 63% yield. However, we also demonstrated that the reaction was particularly sensitive to the steric hindrance of ortho substituents. Thus, substrates such as 2-bromo (2g) and 2-benzamide (2k) diphenyl disulfides gave the corresponding cyanated products in notably lower yields (37% and 31%) than parent 4-substituted compounds. So, thiols 1h and 1l gave 3h and 3l in 51% and 61% respectively.

Conditions: 1 equiv. of thiol or 0.5 equiv. of diphenyl disulfide, 2 equiv. of CuCN in acetonitrile (0.3M) and 2 equiv. of TMEDA in an open vessel for 18h at room temperature.

[a] Performed at 80 °C for 18h; yield evaluated by NMR.

Scheme 2. Scope of copper-mediated cyanation of thiophenols and diaryl disulfides.

As expected, a free hydroxyl group on the substrate (1m) damaged the reaction (3m, 24%) while the corresponding omethylated derivative 1n gave good result (3n, 63%). Gratifyingly, substrates bearing a pyridyl group (2o and 2p), that can unfavorably chelate copper species, were efficiently converted into thiocyanate 3o and 3p in yields up to 94%.

We propose a tentative mechanism based on experimental observation as well as reported mechanistic studies on copper chemistry with thiols. [START_REF] Beletskaya | For a review on C-S metal-catalyzed cross-coupling reactions[END_REF][START_REF] Savarin | For mechanisms of copper-induced reactions involving thiols or disulfides, see for selected examples: a)[END_REF] The first step when starting from the thiol 1a is the complete conversion, almost instantaneously, into the corresponding disulfide 2a as demonstrated by a GC/MS analysis of the reaction mixture after 5 min. Cuprous cyanide could then perform an oxidative addition into the S-S bond to form copper(III) intermediate 4a that could undergo a reductive elimination in order to furnish the desired thiocyanate 3a as well In conclusion, we have developed a practical and mild copper-mediated cyanation of thiophenols and diaryl disulfides. The reaction uses convenient cuprous cyanide as CN source and is performed under air at room temperature, leading readily to variously functionalized aromatic thiocyanates in moderate to very good yields. TMEDA and N-methylimidazole have been determined as efficient promoters of the reaction and acetonitrile as the best solvent. This method represents an interesting complement to existing syntheses of thiocyanates with synthetic potential use in practical oxidative cyanation reaction. At the present time, further studies are under investigations in order to elucidate the mechanism of this transformation and to extend the scope of this approach to different valuable substrates.

Experimental Section

General procedure: To a solution of TMEDA (0.3 ml, 2 mmol) in acetonitrile (3 ml) was added CuCN (179 mg, 2 mmol) and then the disulfide (0.5 mmol) or the thiophenol (1 mmol). The reaction was stirred overnight, at room temperature, under air. The reaction mixture was then filtered through celite pad. The filtrate was evaporated and the crude product was directly purified on silica gel column, or was washed with water and the product extracted with diethyl ether. The product was purified by flash chromatography (heptane/ ethyl acetate).

Supporting Information: (see footnote on the first page of this article): All experimental procedures, characterization data, and copies of the 1 H NMR, 13 C NMR.

Figure 1 .

 1 Figure 1. Relative efficiency of Copper-mediated oxidative cyanation of diphenyl disulfide in various solvents.

Scheme 3 .

 3 Scheme 3. Plausible reaction pathway.

  mild aerobic oxidative CuCN-mediated cyanation of thiophenols and diaryl disulfides is reported. The reaction is performed under air at room temperature and reaches aromatic thiocyanates in moderate to good yields starting from a broad range of diversely functionalized substrates.

Acknowledgements

The CNRS (Centre National de la Recherche Scientifique) and the University of Strasbourg (IDEX PhD grant for T.C.) are acknowledged for financial support. The authors are grateful to Dr. Patrick Wherung from the "Plateforme d'Analyse Chimique Strasbourg Illkirch (PACSI)" for valuable help with HRMS analyses.


F Ahrentorp

A P Astalan

C Jonasson

J Blomgren

Q Bin

O T Mefford

M Yan

J Courtois

J.-F Berret

J Fresnais

O Sandre

S Dutz

R Müller

C Johansson

Sensitive High Frequency AC Suceptometry in Magnetic Nanoparticle Applications

Keywords: AC susceptometer, Brownian relaxation, Néel relaxation, magnetic nanoparticles, magnetic hyperthermia, magnetic characterization PACS: 75.20.Ck, 75.50.Mm, 75.50.Tt, 75.75.Jn

We report on the development of a sensitive high frequency susceptometer capable of measuring in the frequency range from 25 kHz up to 10 MHz with a volume susceptibility sensitivity of 3.5 × 10 -5 at 100 kHz corresponding to about 0.3 % of the measured AC susceptibility. In combination with the previous reported DynoMag system capable of measuring dynamic magnetic properties in the range from 1 Hz to 200 kHz we are thus able to measure dynamic magnetic properties between 1 Hz to 10 MHz with high magnetic sensitivity. We will show AC susceptometry applications and results within the fields of magnetic hyperthermia and dynamic magnetic characterization of magnetic nanoparticle system with different particle sizes and magnetic properties.

INTRODUCTION

AC susceptometry is used in many magnetic nanoparticles applications such as magnetic biodetection [1][2][3], magnetic hyperthermia [4], magnetic characterization of magnetic nanoparticles [5,6] and studies of particle stability [7]. In order to gain as much knowledge as possible it is of great importance to both have high magnetic sensitivity and a large excitation frequency range so that it is possible to cover all the magnetic relaxations that are present in a magnetic nanoparticles system, for instance the Brownian and Neel relaxation processes. High frequency AC susceptometers have earlier been reported using toroidal shaped high permeability material [5] or induction techniques [8]. With the toroidal shaped AC susceptometry systems it is possible to reach up to the GHz range but the magnetic sensitivity is low, the sample mounting it is somewhat complicated and it is very important to clean the measurement slit in the toroid minutely in order to have an accurate background response. For induction techniques AC susceptometers the highest reported measurement frequency is in the range of 1 MHz [8][9]. By using the induction technique with well balanced detection coil system the magnetic sensitivity can be very high, the sample mounting can be easy and the background measurements can be accurate.

Imego have earlier showed results of a high sensitive AC susceptometer (DynoMag ® ) [6] with which it is possible to measure dynamic magnetic properties from a few Hz up to 200 kHz. In order to reach the Neel relaxation frequencies for small particles (below about 12 nm for magnetite nanoparticles at room temperature) we started to develop a high frequency version of the DynoMag system within an EU project FP7-214137-Nano3T. With this new AC susceptometer Imego can today measure dynamic magnetic properties from 25 kHz to 10 MHz combined with a high magnetic sensitivity. Thus, together with the medium frequency range DynoMag system we can measure AC susceptibility in the frequency range from a few Hz up to 10 MHz with a very high sensitivity. In the developed AC susceptometers at Imego we use ordinary induction coil techniques with well balanced differential coils in the centre of an excitation coil and sample movement between in the detection coil system, which will be explained further in the experimental detail chapter. Here we will report on the development of a high frequency AC susceptometer and show results from magnetic nanoparticles applications.

EXPERIMENTAL DETAILS The High Frequency AC susceptometer

A major concern in the design of an induction coil susceptometer is the parasitic capacitance present throughout the coil system, which limit the frequency range of the AC-susceptometer. The inductance, resistance and parasitic capacitance results in a resonance frequency that must be above the highest measurement frequency. Thus, in order to increase this upper frequency limit, the parasitic capacitance must be minimized. Imego has succeeded to minimize the parasitic capacitance, and are able to measure dynamic magnetic properties in the range from 25 kHz to 10 MHz. The system comprises a combination of standard laboratory equipment, signal conditioning electronics, software, and mechanics. The principal building blocks of the system are seen in Figure 1 below. The excitation coil produces the excitation field with field strength of approximately 24 A/m. The detection coil system is in the form of a first order gradiometer, and is located inside the excitation coil. Without a magnetic material in the detection coils, no detection coil signal should be present. Inevitably though, small variations in geometry between the detection coils exist, giving rise to a background signal. In order to detect small magnetic signals from samples with low content of magnetic material or low magnetic susceptibility, these small variations of the two coils have to be compensated for. This is done by moving the sample between the detection coils and measuring the signal in each coil separately. The measurement resolution of the system, defined as the standard deviation of the volume susceptibility measured at 100 kHz and field amplitude 24 A/m, has been found to be 3.5 × 10 -5 ,corresponding to about 0.3 % of the measured AC susceptibility.

The SHP instrument

For the calorimetric determination of the Specific heat Power, SHP, the iron oxide suspensions (usually 1ml) were thermally isolated in PUR foam and placed into a circular coil (diameter 5.5 cm; three turns). In order to measure temperature changes over time during exposure to an alternating magnetic field (amplitudes of 11 and 24 kA/m and frequency 410 kHz were used in the experiments), we used a temperature measuring device with a fibreoptical sensor (OPTOcon, Dresden, Germany). There is no effect of the magnetic field on the sensor.

For thermally equilibrated samples with steady temperatures before exposure to an alternating magnetic field, the SHP was calculated by the following formula:

dt dT m m c SHP p s = (1)
where c is the specific heat capacity of the sample, m p is the total iron oxide particle mass in the suspension, m s is the mass of the sample, dT/dt is the heating rate determined in the linear range (the first ≈30 sec) after switching on the magnetic AC field. Because of the low particle concentration of the samples the specific heat capacity of water was used for the calculation.

We determined the maghemite particle concentration of the dispersions by measuring the specific saturation magnetisation by VSM using either a MicroMag™ 3900 commercial set-up (Princeton Measurements Corp., USA) or a home-made VSM apparatus. We assumed a particle intrinsic saturation magnetisation of 65 Am 2 /kg, which is a typical value for maghemite nanoparticles at room temperature. The magnetization curves used for particle size determination were also determined with the VSM instruments.

Magnetic Nanoparticle Systems

Maghemite Single-Core Nanoparticles Superparamagnetic nanoparticles made of maghemite (γ-Fe 2 O 3 ) were synthesized in water according to Massart's procedure [10]. Briefly, magnetite Fe 3 O 4 nanocrystals were prepared at first by alkaline coprecipitation of a quasi-stoichiometric mixture of iron +II and iron +III salts in HCl (pH≈0.4). Ammonia was quickly added onto the iron salts mixture, which instantaneously produced a black solid suspension. Those Fe 3 O 4 nanoparticles were acidified with nitric acid and then oxidized by adding ferric nitrate. After 30 min at boiling temperature, the suspension had turned to a red colour characteristic of maghemite γ-Fe 2 O 3 . After washing steps in acetone to remove ions in excess, the flocculate was readily dispersed in water to form a true "ionic ferrofluid". The iron oxide surface bears positive charges due to adsorption of protons in the acidic medium, a dilute HNO 3 solution of pH≈1.5. Such a ferrofluid remains in a monophasic state under the application of a magnetic field of arbitrary value. On the microscopic scale, the nano-crystals exhibit a Log-Normal distribution of diameters of parameters D 0 =7.1 nm and σ =0.37, as measured by VSM magnetometry. Maghemite nanoparticles with such a relatively high size polydispersity were treated with a size-sorting procedure based on fractionated phase-separation [11]. More precisely, the addition of more HNO 3 increased the ionic strength and screened the electrostatic repulsions between the nanoparticles. Above a threshold electrolyte concentration, a phase separation occurs between a concentrated "liquid-like" phase and a dilute "gas-like" phase. After magnetic sedimentation on a strong magnet to accelerate demixtion, a culot (denoted C1) could be readily separated from the supernatant (denoted S1). Then the two fractions were washed by acetone to decrease back the ionic strength. Once redispersed in water, we measured again by VSM their size distributions: D 0 =8.8 nm / σ =0.36 for C1 and D 0 =7.2 nm /σ =0.30 for S1. The enrichment of the "liquid-like" phase by the larger size tail of the distribution compared to the dilute "gas-like" phase originates from the sensitivity of the inter-nanoparticle (mainly Van der Waals's) potential with diameters. By repeating the phase-separation steps, we obtained a C1C2 fraction of parameters D 0 =10.7 nm and σ =0.27, and so on until a C1C4 sample characterized by D 0 =11.2 nm /σ =0.32. After the size-sorting procedure, the fractions of interest were coated with polyacrylic acid using a protocol based on electrostatic complexation and adsorption. Poly(sodium acrylate), the salt form of PAA 2K of molar mass M W = 2000 g mol -1 and molar mass dispersity of 1.7 was purchased from Sigma Aldrich. In order to adsorb polyelectrolytes onto the surface of the nanoparticles, we followed the precipitation-redispersion protocol [12]. The precipitation of the cationic iron oxide dispersion by PAA 2K was performed by mixing at pH 2. Then the precipitate was separated from solution by centrifugation and its pH was increased with NH 4 OH. The precipitate redispersed spontaneously at pH≈7.5, yielding a clear solution of polymer coated particles. The hydrodynamic sizes of those γ-Fe 2 O 3 @PAA 2K core-shells were found 5 nm larger than the uncoated particles, indicating a corona thickness h=2.5 nm [13] The surface coverage on nanoparticles was estimated to be around 1 adsorbed chain per nm -2 . As a final step, the dispersions were dialyzed (Spectra Por 2 MWCO=12 kD) against DI-water. The pH being adjusted to 8, 90 % of the carboxylate groups of the PAA coating were ionized, as stated by their ζ potential -50mV for a hydrodynamic size Z ave =36nm (measured for C1C4@PAA 2K with a Malvern NanoZS operating at 173°). An additional treatment by magnetophoresis on a strong magnetic field gradient was performed overnight [14]. Unlike the addition of excess electrolyte, this procedure does not work on a true phase-separation but simply on the formation of a vertical concentration profile: by pipetting at the bottom of the flasks next to the magnet, we obtained fractions denoted C1C2@PAA 2K -sed and C1C4@PAA 2K -sed with a slightly larger tail of the distribution towards the largest diameters.

Table 1 shows the particle size parameters of the prepared maghemite nanoparticles determined with VSM analysis i. e. the magnetization, M, was fitted to the Langenvin expression L(...) integrated over a Log-Normal size distribution, f LN , according to:

∫ = dV V f kT VH M VL M V M LN S S S ) ( ) ( 1 0 μ (2)
where V S is the volume of the sample, M S the intrinsic saturation magnetization (65 Am 2 /kg, typical for maghemite nanoparticles), V the volume of the particles, μ 0 the permeability of free space, k the Boltzmann's constant and T is the temperature. * <d 6 >/<d 3 >) 1/3 =d 0 exp(4.5σ 2 ) according to <d n >=d 0 n exp(nσ 2 /2) for the n th order moment of a Log-normal law.

The samples were further analyzed by Transmission Electron Microscopy (TEM) on a JEOL100 microscope operating at 80kV. A TEM picture of a representative area of sample 3 can be seen in figure 3. From TEM analysis, the diameter averaged on 237 particles was d TEM =17.9 nm. We estimated also the weight-averaged diameters of the samples by calculating the 3 th and 6 th order moments of the Log-normal distributions deduced by VSM (Table 1). We found d VSM =17.7 nm for sample 3, which well compares to d TEM from the analysis of the electron micrographs. The slight deviation may be ascribed to the magnetic anisotropy and magnetic interactions not included in this VSM analysis using only Langevin's function integrated over a size distribution according to equation 2 [15,16].

Magnetite Single-Core Nanoparticles

Ferric chloride anhydrous was purchased from Spectrum Chemical, sodium oleate was purchased from TCI, oleic acid (90%) and hexane (95+%) were purchased from Alfa Aesar, ethanol, anhydrous was purchased from Fisher Scientific. All chemicals were used directly without further purification. Particles were synthesized based on methods previously reported by Park et al [17]. Particles were formed by first creating an iron-oleate complex. This complex was then thermal decomposed at elevated temperatures yielding the monodisperse particles. First, an ironoleate complex was formed. Briefly, 10 mmol of ferric chloride and 30 mmol of sodium oleate were dissolved in a mixed solvent composed of 20 ml ethanol, 15 ml distilled water, and 35 ml hexane. This solution was then heated to 70°C and held at this temperature for four hours. After cooling down to room temperature, the solution separated into to two layers, and then the upper organic layer was washed 3 times with 30 ml distilled water in a separatory funnel to remove residual hexane. The resulting iron-oleate complex was a waxy solid form.

To form the nanoparticles, 10 mmol of as prepared iron-oleate complex and 20 mmol of oleic acid were dissolved in 64 ml of 1-octadecene at room temperature. Then the mixture was heated to 320 °C with the ramping rate of 3.3 °C/min, and kept to reflux at that temperature for 30 min, then cooled to room temperature by removing the heating source. Nanoparticles were precipitate out by adding 100 ml ethanol into the prepared solution. The nanoparticles were separated by centrifugation and washed by the mixture of ethanol and hexane (volume ratio 1:1) for five times and then redispersed in hexane. Particles for high-resolution transmission electron microscopy (HR-TEM) characterization were obtained by drying a dispersion on copper grid coating with carbon film, and then tested by Hitachi H-9500 (300 kV), see figure 4. Then the images were analyzed by FOVEAPRO 4.0 and the data were calculated by KaleidaGraph to obtain size histogram. The as prepared nanoparticles were diluted by hexane and characterized via dynamic light scattering (DLS, Malvern Instrument Nano-ZS) to measure their hydrodynamic volume. The volume weighted hydrodynamic diameter determined by the DLS analysis was found to be about 30 nm.

FIGURE 4.

To the left a TEM image of the 20 nm magnetite nanoparticles deposited on copper grid coating with carbon film. The scale bar is 100 nm. To the right size distribution histogram of as synthesized 20 nm magnetite nanoparticles. The mean value of the particles in diameter is 18.9 nm, with the standard deviation of 2.8 nm.

Magnetite Multi-Core Nanoparticles

We analyzed also the dynamic magnetic properties of Nanomag-D nanoparticles with a diameter of 130 nm from Micromod Partikeltechnologie GmbH. These particles are magnetic multi-core particles meaning that the particles contain a large number of single-domains. The single-domains are magnetite crystals with diameters in the range of 12 nm.

RESULTS AND DISCUSSION

Magnetic Hyperthermia Applications

Magnetic hyperthermia using magnetic nanoparticles relies on the fact that the particle system absorbs energy when it is subjected to an alternating magnetic field at a specific frequency. The amount of energy absorbed depends on the magnetic loss of the magnetic nanoparticle system. In order to optimize the energy absorption of the nanoparticle system the size of the particles has to be fitted to the used hyperthermia frequency and the size distribution has to be as low as possible. In order to determine the magnetic loss spectra in a large frequency range for a nanoparticle system it is very straightforward to use high frequency AC susceptometry that covers the used hyperthermia frequency range. From the AC susceptometer data the specific heat power absorption, SHP, expressed in W/g can be estimated in a large frequency range. The traditional way to do this is to approximate that the amplitude of the imaginary part of the magnetization, M'', is linear to the excitation field amplitude, H 0 , and P is then given by [4].

S V fH SHP 2 0 0 ″ = χ πμ (3)
where f is the frequency and χ'' is the imaginary component of the susceptibility. However, at large field amplitudes the magnetization is no longer linear to the field as can be seen from figure 5. At the highest field amplitude used in this study (24 kA/m) the ratio of magnetic energy to thermal energy (

kT VH M S / 0 μ
) is about 2 and as we can see from figure 5 the magnetization is no longer linear to the field at these field strengths. In order to take into account the non-linear response we propose that the measured magnetization curve, M exp , and the measured imaginary part of the AC susceptibility normalized to the static susceptibility (f=0), ' ' χ , can be used to estimate the non-linear field dependence of the imaginary part of the magnetization, M'', and SHP values can then be estimated according to. Further, the shape of M'' versus field is deviating from an ellipse at high fields and the exact curve shape and thereby the true loop area (absorbed energy) can also be determined at higher field amplitudes. When the temperature increase in the nanoparticle system, the susceptibility value decreases (according to a Curie law for noninteracting particles) and the relaxation frequency (Néel relaxation) is shifted to higher frequencies. All of the temperature effects will decrease the dynamic magnetic response at the used SHP frequency (410 kHz) since the relaxation peak is at about at 1 MHz, see figure 6 showing the AC susceptibility versus frequency for sample 4. When we take all these effects into consideration, we can estimate the SHP values from the AC susceptometry analysis described above. The results can be seen in table 2.

TABLE 2.

The table shows the measured SHP values in W/g(magnetic material) for the maghemite single-core nanoparticles at two different field amplitudes and the estimated SHP values from the AC susceptometry measurements. All the measurements were carried out with the particles in solution. As can be seen from table 2 the resemblance between the measured and estimated SHP values is good especially at the lower field amplitudes. At the high field amplitudes there are some discrepancies between measured and estimated values, which can be explained by the fact that at higher field amplitudes, higher orders of the dynamic magnetic response [18] have to be taken into account. In addition, at higher field amplitudes the effect of particle clustering due to magnetic interaction can increase which will influence the dynamic magnetic response. It is however seen that some of the non-linear effects can be explained by the non-linear response from the magnetization curve. The field dependence in the measured SHP values can also be predicted by using equation 4.

Sample

Dynamic Magnetic Characterization Applications

For a general magnetic material, AC susceptometry gives information of the different magnetic relaxations that are present in the magnetic system. For a magnetic nanoparticle system in a carrier liquid both the Brownian relaxation and the Néel relaxation can be present depending on the size of nanoparticles for a specific material in the nano-particles, carrier liquid, and the temperature in the nanoparticle system. The magnetic response as a function of the excitation frequency, f, can be represented by the susceptibility component that is in the phase with the excitation field (the real part) and the susceptibility component that is in quadrature to the excitation field (the imaginary part).

Maghemite Single-Core Nanoparticles

One example of dynamic magnetic measurements where we used both the DynoMag system from 10 Hz to 200 kHz and the high frequency AC susceptometer from 25 kHz to 10 MHz can be seen in figure 6 for sample 4 of the maghemite nanoparticles. From figure 5 we can see that there is a very good overlap between the two used AC susceptometers. The peak in the imaginary part of the susceptibility at about 2 MHz is due to the internal Néel's relaxation of the nanoparticles. From the above result for the single-core maghemite particle system (sample 4) we can fit the data to a single-core Debye model according to:

( ) ( ) ( ) ( ) high H H H eff C dr r f r j r C χ ωτ ω χ + + = ∫ 1 6 (5)
Where the pre-factor, C, is dependent on the temperature and the intrinsic saturation magnetization, r C the radius of the magnetic core, f(r H ) is the size distribution (log-normal) of the hydrodynamic radius, r H , of the particles, ω=2πf, j equal to 1 and χ high is the high frequency response for instance due to the intra-well potential contribution to the AC susceptibility [19]. In the fitting procedure the hydrodynamic radius and magnetic core radius were set equal (i. e. r C = r B ). The effective relaxation time, τ eff , is given by: where η is the viscosity of the carrier liquid. In the size analysis we used a value of the magnetic anisotropy to be 3 × 10 4 J/m 3 [16] a typical anisotropy value for maghemite nanoparticles in this size range. The results from the above described particle size analysis gives a median particle diameter of 11.5 nm that are well matched with the obtained VSM size analysis, 11.5 nm, as described in the experimental chapter.

B N τ τ τ 1 1 1 eff + = (6)

Magnetite Single-Core Nanoparticles

AC susceptibility versus frequency of the 20 nm magnetite single-core nanoparticles can be seen in figure 7. The relaxation peak at about 5 MHz is due to the Néel relaxation. Since the magnetite single-core nanoparticles has a mean diameter of about 20 nm and that the Néel relaxation peak is as high as 5 MHz the effective magnetic anisotropy must be small compared to other magnetite single-nanoparticles in this size range.

Magnetite Multi-Core Nanoparticles

Another example of the AC susceptometry measurements can be seen in figure 8 where we have measured on the Nanomag-D 130 nm magnetite multi-core particles from Micromod. The peak in the imaginary part at about 350 Hz is due to Brownian relaxation consistent with the particle diameter of the particle system. If we use a multi-core model and fitting the AC susceptibility [6] we can estimate a particle hydrodynamic diameter of about 130 nm which is consistent with the specification from Micromod. Note that all the single domains in this particle system are thermally blocked with respect to the particle rotation since no Néel's relaxation can be observed at higher frequencies (> 1 MHz). The non-zero value of the real part above the Brownian relaxation frequency is probably due to the intra-potential-well contribution to the AC susceptibility [19].

CONCLUSIONS

We have shown that AC susceptometry based on induction techniques is a valuable magnetic characterization tool for magnetic nanoparticles for instance within the fields of magnetic hyperthermia and for dynamic magnetic analysis of magnetic nanoparticles. When the proper non-linear field dependence of the magnetization is taken into account SHP values can be estimated from the AC susceptometry analysis with good accuracy when compared to measured SHP values. When the full high frequency AC susceptometer response is analyzed for nanoparticles undergoing Néel's relaxation, the particle sizes can be estimated or the magnetic anisotropy if the particle sizes are known from other independent analysis techniques for instance size analysis from VSM data.

FIGURE 1 .

 1 FIGURE 1. The principal building blocks of the Imego high frequency AC susceptometer, consisting of AC signal source (A), current amplifier (B), coil system and mechanics (C), lock in amplifier (D), and user interface software (E).

FIGURE 2 .

 2 FIGURE 2. Setup for determination of the SHP consisting of the field generating coil driven by a HF generator as well as the temperarture measuring system with a fibreoptical sensor

FIGURE 3 .

 3 FIGURE 3. A representative TEM picture (left) of sample 3 of the maghemite nanoparticles (bar length is 100nm) and a size histogram (right) of the diameters of the nanoparticles.

FIGURE 5 .

 5 FIGURE 5. Magnetization curve for sample 4. The used field amplitudes in the SHP determination are 11 kA/m and 24 kA/m. The linear line is the extrapolation of the low field linear portion of the magnetization curve to higher fields.

FIGURE 6 .

 6 FIGURE 6. AC susceptibility, real (upper curve) and imaginary part (lower curve) versus excitation frequency of sample 4 at 300 K. The solid line is the result of the fitting to the single-core model as described in the text. Measurements are carried out with the particles in solution (water).

  τ 0 is characteristic relaxation time in the range of 10 -9 s -10 -10 s, K the magnetic anisotropy and V is the volume of the single-domain. The Brownian relaxation time τ B is given by

FIGURE 7 .

 7 FIGURE 7. AC susceptibility (the real and imaginary part) versus excitation frequency of the magnetite single-core nanoparticles at 300 K. Measurements were carried out with the nanoparticles in solution (hexane).

FIGURE 8 .

 8 FIGURE 8. AC susceptibility, real (and imaginary part versus excitation frequency of nanomag-D 130 nm particle system from Micromod at 300 K. Measurements were carried with the nanoparticles in solution (water).

TABLE 1 .

 1 Particle size parameters, median diameter D 0 and standard deviation σ determined from the VSM analysis described in the text.

	Sample	D 0	σ	Weight-
		(nm)		averaged*
				diameter (nm)
	1=C1C2@PAA 2K	10.7	0.27	14.8
	2= C1C2@PAA 2K -sed	11.5	0.25	15.2
	3= C1C4@PAA 2K	11.2	0.32	17.7
	4= C1C4@PAA 2K -sed	11.5	0.25	15.2

ACKNOWLEDGMENTS

We would like to acknowledge Micromod Partikeltechnologie GmbH for providing the Nanomag-D particle systems. We would also like to acknowledge the EU project Nano3T FP7-214137-Nano3T for financial support.


Barnett redivivus

VS

In the spring of 2001, while surveying the scholarship on the mysterious Lettres portugaises, I encountered an annoying bibliographical redundancy: a seemingly new article by Richard-Laurent Barnett, published in 1997 in the American journal Romanic Review, was in fact identical to a chapter in Barnett's book Dynamics of Detour (Tübingen: Gunter Narr, 1986). Another chapter from this book, on Pascal, had been similarly reprinted in 1998 in the German journal Zeitschrift für französische Sprache und Literatur. In both cases, only the titles, some footnotes, and a few expressions had been modified; the substance of the essays remained the same. There was no reference to the original publication.

Further research in the library stacks revealed that between 1990 and 2000 Barnett had also managed to recycle an essay on Corneille three times, as well as two essays on Racine (one in English, the other in French) three and five times, respectively -always changing the titles and little else. While not totally inconsistent with certain usages of academic publishing, this case of systematic self-plagiarism struck me as unprecedented and noteworthy. Dutifully, I informed the various journal editors (who were, of course, unaware that they had reprinted previously published texts) and presented my findings to the scholarly community in the guise of a book review.

During the following years, there were no more publications by Barnett on 17 -century literature, except for three additional iterations of his French-language essay on Racine.

Instead, his focus manifestly shifted towards modern topics, with articles on writers such as Michaux, Modiano, and Cioran, as well as general questions of literary theory. I did not observe this phase closely but noticed, en passant, that the author's name now appeared often as "R.-L. Étienne Barnett" and that he continued to move restlessly from one academic leadership position to the next, with an increasing specialization in forprofit distance education. Notwithstanding these variable identities and titles, Barnett did seem to be an actual person, if one was to believe the memories shared by those who had had the rare privilege of meeting or working with him, as well as the few photos that were publicly available. Modestly, the book makes no mention of the previous publications of these essays; instead, in inimitably Barnettian fashion, it cites numerous other books and articles, recent or forthcoming, whose existence is difficult and perhaps impossible to verify. This protean updating of bibliographical references extends here to the work of other critics: for example, a statement about epistolary communication that was, in 1986 and 1997, correctly attributed to Susan Lee Carrell, is now credited enigmatically to "Vallois, C. E.

(2014). Le nouveau roman épistolaire: énigmes et interrogations. Zurich: Haldenn." Also worth reading are the eloquent epigraphs scattered throughout the collection: far from being straightforward quotations, many offer creative adaptations and alterations of the originals, and more than a few appear to show the author generously lending his own words to other famous writers, in a curious gesture of reverse plagiarism.

While the praise bestowed upon the book by its editor may be excessive (and the prizes it is said to have won chimeric), there is no doubt that The Adversarial Text / Le Texte adversaire provides in its 230 pages a compelling and beguiling sample of Barnett's work from three decades and deserves to be studied as such. According to WorldCat, among American universities only Harvard and Missouri-Columbia have so far acquired a copy. Other libraries will hopefully follow suit so that this remarkable volume, which is likely to remain the definitive embodiment of the author's unique genius, can be more widely read and appreciated.

Volker Schröder June 12, 2018

  Whereas my 2001 review had rather limited repercussions, intended as it was for the small circle of fellow dix-septiémistes, in late 2014 Barnett gained broader notoriety thanks to a long exposé by Michel Charles, an eminent literary theorist and editor of the journal Poétique. Charles demonstrated that 35 articles published by Barnett since 1999 in 10 different journals were verbatim copies of 19 essays originally written by others. Posted online on Fabula, the leading French portal for literary research, this 8000-word piece was widely shared and commented. It also prompted some of the affected publishers to conduct their own investigations, resulting in a wave of retractions, explanations, and apologies. The Hungarian journal Neohelicon, in particular, retracted no fewer than 13 articles signed by Barnett that it had diligently published in the years 2006-2014. Several journals expelled him from their editorial boards and terminated all collaboration. Ordinary academics might have been discouraged by such draconian reprisals, but Barnett's singular passion and persistence have allowed him to bounce back quickly and strongly, as evidenced by his latest publication: not a mere journal article, but an awardwinning book bilingually titled The Adversarial Text / Le Texte adversaire (Fasano:Schena / Paris: Alain Baudry, 2017). this title was announced by Barnett as early as 1998, but it took another two decades of collective efforts for the project to come to fruition. Among the 11 "chapters" are indeed 4 of the plagiarized articles retracted by Neohelicon (originally written by René Audet, Jan Baetens, Lucien Dällenbach, and Jacques Poirier). But more interestingly for the field of 17 -century studies, the collection also gives new life to some of Barnett's own essays, including (as chapters 1-5) the above-mentioned ones on Corneille, Pascal, Racine, and the Lettres portugaises. While these can all be found online in at least one of their prior incarnations, most of them had not yet been physically reprinted in the current millennium and were at risk of fading into oblivion.

Footnotes 1 .

 1 To this list needs to be added the following article on Racine, which I did not know when writing my review: Richard-Laurent Barnett's "Les enjeux du schisme: essai d'herméneutique racinienne" (Revue d'histoire du théâtre 52, 2, avril-juin 2000) reproduces Marcel Gutwirth's "Jéhu, le fier Jéhu: la métaphorisation du tragique" (Relectures raciniennes, ed. Richard L. Barnett, Paris-Seattle-Tübingen: Papers on French Seventeenth Century Literature, 1986). 2. See Giovanni Dotoli, "Au seuil de l'indicible: avant-lire" (The Adversarial Text / Le Texte adversaire, p. 9-12). Different versions of this presentation also appeared in the review sections of the following journals: Revue européenne de recherches sur la poésie (3, 2017); Studi di letteratura francese (42, 2017); Skené (8, 2018).

  th


Volker Schröder

Philippe Hourcade

ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

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The Engraved frontispieces face the title pages of volumes 1 and 3. The first of these images has already been known from another copy of volume 1, which was sold on eBay in 2008; fortunately, it was captured and posted online on the blog of "Le Bibliomane moderne" (the French bookseller Bertrand Hugonnard-Roche). In her excellent study of early fairy-tale illustrations, Daphne Hoogenboezem doubted the authenticity of this frontispiece and suggested that it was a later addition by an individual owner of the book. Its presence in the WLB copy, however, confirms that at least some of the copies sold by Claude Barbin were indeed issued with this frontispiece. Whether the author had any control over its design and execution is another matter; none of d'Aulnoy's earlier books were illustrated, and Barbin may well have proceeded without consulting her.

Whatever its origins and intentions, this frontispiece must now be taken into account as the earliest visual representation accompanying and introducing Les Contes des fées. The presence of the same engraved vignettes and woodcut ornaments in both copies shows that we are confronted not with a piracy but two "original" editions, both published by Claude Barbin and printed by the same printer (probably Jacques Langlois). Such cases of duplicate editions are surely more frequent than bibliographers have realized; in fact, Barbin's 1697 edition of Perrault's tales exists itself in two versions, which have often been erroneously described as two "states" or "printings" (tirages) of a single edition, when in reality most of the text was reset.

In the case of Perrault's tales, an errata leaf helps distinguish the first edition from the second. No such supplement differentiates the UCB and WLB copies of volume 1 of Les Contes des fées, and a more thorough comparison will be needed to determine which of the two may have been printed first. As far as volume 2 is concerned, the three currently known copies (preserved in Stuttgart, Gotha, and Madrid) all seem to belong to the same edition, but one can hope that additional copies will surface and shed more light on the publication history. In the meantime, the newly located volumes present d'Aulnoy scholars not only with two new frontispieces, but also with hundreds of (small but not insignificant) textual variants awaiting identification and critical appraisal.

Volker Schröder

April 10, 2018

  Fr.D.oct.1816-4

  It is perhaps in reaction to this rather frightening image of a stern matron or mistress that volume 3 opens with a much gentler vision of female storytelling. This frontispiece (reproduced here for the first time) is signed "Clouzier. F." -with "F." being not a first name initial but the abbreviation of "Fecit." The same signature appears in three of the five vignettes in volume 4. It probably refers to the engraver Antoine Clouzier, who often worked for Barbin and also executed the famous frontispiece to the tales of Perrault, published the same year. (The comparison between these two frontispieces signed by Clouzier lies beyond the scope of this note.) By contrast, none of the illustrations in volumes 1 and 2 are signed; on stylistic grounds, I would question their traditional attribution to Clouzier. Württembergische Landesbibliothek, Fr.D.oct.1816-3 Another copy of volume 1, also dated 1698 but lacking the frontispiece, was acquired by the University of Colorado Boulder in 2007 and digitized in 2011. While at first it looks identical to the WLB copy, closer examination yields a surprise: the two books were actually printed, for the most part, from different settings of type and thus represent (bibliographically speaking) two different editions. Their non-identity is almost imperceptible on some pages, but conspicuous on others: left: University of Colorado Boulder / right: Württembergische Landesbibliothek left: University of Colorado Boulder / right: Württembergische Landesbibliothek


Volker Schröder

Volker Schröder More Madame D'

Aulnoy 2018 Halshs-02320588

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Aulnoy Vs

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I am happy to report that all four volumes of Contes nouveaux have survived and can be consulted in New York, at the Hispanic Society of America. What may at first appear to be an unlikely place for such a rare find actually makes a lot of sense. D'Aulnoy first achieved international fame by her writings on Spain, which were read throughout Europe and quickly translated into English, German, and Dutch. Her fairy tale collections also contain many Spanish elements, especially in the frame narratives. The Hispanic Society was founded by Archer Milton Huntington (1870-1955), a scholar, collector, and philanthropist with a lifelong passion for Spanish and Latin American

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The If the Contes des Fées of Madame Aulnoy have had a remarkable vogue, not so fortunate has been the lot of some of the historical endeavors of this lady.

[…] she describes her voyage into Spain with a brilliancy and wealth of detail which is all the more grateful in that the period has furnished us with but little like it. In this Journey she has produced a remarkable book. Volume 3, however, has its own original frontispiece, never before discussed and here reproduced for the first time:

The Hispanic Society of America This image offers yet another scene of female storytelling, and surely the most intimate and graceful one. The teller/"fairy" here is not a hag, nurse, or sibyl, but a young,

  literature and art. In 1892, he first traveled to Spain to follow the route of El Cid. In 1898, he included several quotations from "Madame Aulnoy" in his Note-Book in Northern Spain. The following year, he published a reprint of The Ingenious and Diverting Letters of the Lady -----Travels into Spain, a 1692 translation of d'Aulnoy's Relation du voyage d'Espagne. In his Introduction, Huntington explained the reasons for this publication:

Archer

  Huntington in Spain, 1892 (The Hispanic Society of America) It is not known when and where Archer Huntington acquired his copy of d'Aulnoy's Contes nouveaux. It probably came from the collection of his mentor, Yale professor William I. Knapp, most of whose books passed on to Huntington. Three of the volumes are signed or stamped by earlier owners: "Jacques Carbon" (vol. 2); "Bibliotheca Adr. Maillart Adv. Paris 1741" (vol. 3); "Marie Marthe Olimart" (vol. 4). These different provenances suggest that the set was patiently assembled by a 19th-century dealer or collector because a "better" copy was impossible to find. The 1898 auction of the library of the French bibliophile baron Jérôme Pichon included a set with similar characteristics (no. 3508: "exemplaire fatigué; reliures non uniformes"), but the description is not detailed enough to provide any certainty. The Hispanic Society copy of Volume 1 lacks the Epistre -but more importantly, it does include a frontispiece: The Hispanic Society of America In this programmatic image, an old woman with glasses and a turban (reminiscent of the Cumaean Sibyl in the Sistine Chapel) reads a large book before a pair of children, while another child (or putto?) is playing with a monkey. The open book displays the running title "Contes des fées"; the rest of the text is not legible. First analyzed 25 years ago in a seminal article by Gabrielle Verdier, this frontispiece has often been reproduced and commented, but always on the basis of the 1711 edition, in which it 1 appears at the beginning of Volume 3, entitled Suite des Contes nouveaux. The date of its first publication had remained uncertain: while Verdier argued that it must have already been part of the first edition, other critics have speculated that it was created later, as a posthumous homage to d'Aulnoy (who died in 1705). The New York copy settles this debate and confirms that the frontispiece indeed appeared in 1698 -and with the first volume, not the third.

  elegantly dressed woman surrounded by four children. Her winding wool into a ball evokes the spinning traditionally associated with popular storytelling, an association reinforced by the etymological proximity between fairies and the Fates. The infant in the cradle may be a variation on the iconographic motif of the sleeping Jesus watched over by the Virgin Mary and John the Baptist, as in Michelangelo's "Madonna del Silenzio." Like the first frontispiece (where the woman's mouth is clearly closed), the image appears to suggest both speech and silence, perhaps in an attempt to instill in the reader an attitude of attention and a sense of mystery. Both these frontispieces, as well as all the half-page vignettes in the four volumes of Contes nouveaux, are signed "Raymond [or: Raimond] Fecit [or: f.t]." This seems to refer to the little-known engraver Jean Raymond, who also illustrated a 1703 edition of Aesop's fables (using the signature "I Raymond fecit"); in his later career he produced a number of large-scale reproductive prints, and died in 1736. Raymond's style is markedly more delicate and sophisticated than that of Antoine Clouzier, who signed the illustrations for volumes 3 and 4 of Les Contes des fées. The change of engravers was linked to a change of publishers: whereas Les Contes des fées appeared with Claude Barbin, who had published all of d'Aulnoy's books in the 1690s (except the first), she gave her Contes nouveaux to Catherine Legras, widow of the bookseller Théodore Girard. In June 1698, Girard and Legras' former apprentice Nicolas Gosselin took over the shop: the Hispanic Society's copy of Volume 2 already shows his name on the title page, whereas the BnF copy still says "chez la Veuve de Théodore Girard." Volumes 3 and 4, the printing of which was completed in July 1698, were published under the imprint of Gosselin. I am inclined to believe that d'Aulnoy's move away from her longtime publisher Barbin had something to do with the question of illustration. The work of Raymond is certainly superior to that of Clouzier, and more in sync with the author's literary art and outlook. The frontispiece to Volume 1 of Contes nouveaux can be seen as a revision of that to Volume 1 of Les Contes des fées (both featuring an old woman with a book); likewise, the gentler, maternal images that introduce the respective third volumes appear to mirror each other. While many aspects of the publication history of d'Aulnoy's eight volumes of Contes remain mysterious, the copies mercifully preserved in Stuttgart and New York provide a wealth of new textual and visual material and call for closer inspection. Verdier, "Figures de la conteuse dans les contes de fées féminins," XVIIe siècle 45, 3, July-September 1993, p. 481-499. Left: Les Contes des fées, vol. 1 and 3 (Württembergische Landesbibliothek Stuttgart) / Right: Contes nouveaux, vol. 1 and 3 (The Hispanic Society of America)

Subscribe to Blog via Email Enter your email address to subscribe to this blog and receive notifications of new posts by email. Email Address Subscribe Anecdota Rare texts and images from early modern France About

	birth and beginnings
	of Madame d'Aulnoy
	Bussy-Rabutin's Book of
	Hours
	More Madame d'Aulnoy
	Barnett redivivus
	Les Contes des fées
	Marie-Madeleine Perrault
	(1674-1701)
	Rubens and the King of
	France
	Only in Lyon
	Ex bibliotheca R. Toinet
	Saving Madame de
	Graffigny