Oxidation of the square planar Rh(I) complex [Rh(SPS Me )(PPh 3 )] (SPS Me ) 1-methyl-1-P-2,6-bis... more Oxidation of the square planar Rh(I) complex [Rh(SPS Me )(PPh 3 )] (SPS Me ) 1-methyl-1-P-2,6-bis(diphenylphosphinosulfide)-3,5-(bisphenyl)-phosphinine) (1) based on mixed SPS-pincer ligand with hexachloroethane yielded the Rh(III) dichloride complex [Rh(SPS Me )(PPh 3 )Cl 2 ] (2), which was structurally characterized. The homoleptic Rh(III) complex [Rh(SPS Me ) 2 ][Cl] (4) was obtained via the stoichiometric reaction of SPS Me anion (3) with [Rh(tht) 3 Cl 3 ] (tht ) tetrahydrothiophene). Complex 4, which was characterized by X-ray diffraction, was also studied by cyclic voltammetry. Complex 4 can be reversibly reduced at E ) -1.16 V (vs SCE) to give the neutral 19-electron Rh(II) complex [Rh(SPS Me ) 2 ] (5). Accordingly, complex 5 could be synthesized via chemical reduction of 4 with zinc dust. EPR spectra of complex 5 were obtained after electrochemical or chemical reduction of 4 in THF or CH 2 Cl 2 . Hyperfine interaction with two equivalent 31 P nuclei was observed in liquid solution, while an additional coupling with a spin 1 / 2 nucleus, probably 103 Rh, was detected in frozen solution. The 31 P couplings are consistent with DFT calculations that predict a drastic increase in the axial P-S bond lengths when reducing (SPS Me ) 2 Rh(III). In the reduced complex, the unpaired electron is mainly localized in a rhodium d z 2 orbital, consistent with the g-anisotropy measured at 100 K.
Intramolecular motion in dibenzobarrelenephosphinyl radical: A single crystal EPR study at variab... more Intramolecular motion in dibenzobarrelenephosphinyl radical: A single crystal EPR study at variable temperature
The nonlinear algorithm SIMPLEX of Nelder and Mead is suitable for the minimization of a general ... more The nonlinear algorithm SIMPLEX of Nelder and Mead is suitable for the minimization of a general nonlinear function of several variables. It has been widely used for many years and appreciated for its simplicity and robustness. It does not however converge very fast.
International Journal of Radiation Applications and Instrumentation. Part C. Radiation Physics and Chemistry, 1991
X-irradiation of a single crystal of bromonitrothiazole at 77 K leads to signals in both the g = ... more X-irradiation of a single crystal of bromonitrothiazole at 77 K leads to signals in both the g = 4 and the g = 2 regions of the ESR spectrum. The angular dependence of these signals is consistent with the formation of a radical pair which exhibits hyperfine structure with a 1 H and 14 N ...
Journal of Physics E: Scientific Instruments, 1977
A description is given of a device which allows the precise orientation of a single crystal in an... more A description is given of a device which allows the precise orientation of a single crystal in any given direction with respect to the static magnetic field. It particularly facilitates the ESR analysis as it gives the angular dependence of the ESR signals in the principal planes.
ABSTRACT In addition to the formation of Ph3Sn.;, X-irradiation at room temperature of tetrapheny... more ABSTRACT In addition to the formation of Ph3Sn.;, X-irradiation at room temperature of tetraphenyltin single crystals results in the trapping of a second tin-centred radical. The g tensor and the 117Sn/119Sn hyperfine coupling tensors are shown to be consistent with the identification of Ph5Sn.. A reaction mechanisms is suggested.
The paper shows the possibilities of the complementary use of the density matrix formalism for th... more The paper shows the possibilities of the complementary use of the density matrix formalism for the simulation of the anisotropic EPR spectra and the DFT potential energy surface calculations to obtain a detailed picture of the motions of radical molecules. The combined approach is illustrated by a comparative EPR study of three phosphorus derivatives of barrelene. Three compounds were chosen as the model molecules for the observation of different temperature depend-ent dynamics of radical fragment. Each molecule based on the same barrelene skeleton has a different set of substitu-ents which by influencing the local chemical environment are likely to modify the internal dynamics. The temperature dependent EPR spectra are simulated by means of the density matrix formalism and the geometry of radicals are calcu-lated with DFT. The motion is described in terms of rotational barriers, DFT calculated energy profiles and hypotheti-cal intramolecular distortions. These two approaches lead t...
La spectroscopie de résonance paramagnétique électronique permet d'accéder à des informations... more La spectroscopie de résonance paramagnétique électronique permet d'accéder à des informations sur l'interaction des moments magnétiques électroniques (spins) avec le champ magnétique appliqué (effet Zeeman) et avec les moments magnétiques nucléaires des noyaux voisins (interactions hyperfines). Si l'on dispose d'un modèle mathématique pour simuler des spectres de RPE de poudre par le calcul, les spectres de poudre expérimentaux permettent de déduire des paramètres spectroscopiques. Dans ce but, on minimise la somme des carrés des écarts entre les valeurs échantillonnées des signaux observé et calculé. La différentiation automatique combinée à la double précision permet de faire converger la minimisation en un petit nombre d'itérations.
Journal of the Chemical Society, Faraday Transactions, 1995
Bis(N-methylimidazolidinethi-2-one)copper(I) chloride has been synthesized and its crystal struct... more Bis(N-methylimidazolidinethi-2-one)copper(I) chloride has been synthesized and its crystal structure determined. X-Irradiation of a single crystal of this compound leads to the formation of a CuII complex which was studied by EPR: it was shown that this species results from the addition of a radiogenic Cl atom on the CuI precursor. The structural changes induced by this reaction are revealed by the g-tensor and by the hyperfine tensors of one copper and two chlorine nuclei. The structure of this S2Cl2Cu type complex was compared with other sulfur- or chlorine-containing CuII complexes.
Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases, 1988
ABSTRACT The crystal structure of the title phosphated sugar (I) has been determined. The angular... more ABSTRACT The crystal structure of the title phosphated sugar (I) has been determined. The angular variations of the e.s.r. spectra obtained with a single crystal of (I) X-irradiated at T≈ 100 K have been analysed. They show that a radical pair is produced by irradiation and that a component of this pair is a phosphoryl radical. The orientations of the e.s.r. tensors are compared with the crystallographic bond directions and the role of the irradiation conditions on pair formation is examined. It appears that the phosphoryl radical is probably produced by electron capture by the cationic species [(RO)3PO]+.
Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases, 1987
ABSTRACT Single crystals of 1,2-o-isopropylidene-3,5-o-phenoxyphosphoryl-α-D-xylofuranose have be... more ABSTRACT Single crystals of 1,2-o-isopropylidene-3,5-o-phenoxyphosphoryl-α-D-xylofuranose have been X-irradiated at low temperature (ca. 77 K) and studied by e.s.r. spectroscopy. The angular dependence of the signals has led to the identification of four radicals: a phosphoranyl-type radical, two phosphonyl species and a radical pair, one of whose components is a phosphonyl-type radical. The 31P-hyperfine tensor has been obtained for each species and the pair has been characterized by its electron–electron dipolar interaction. It is shown that electron capture by a PO bond and homolytic scission of the various P—O bonds are involved in the radiation damage process.
X-irradiation of single crystals of triphenylmethylarsonium chloride at room temperature produces... more X-irradiation of single crystals of triphenylmethylarsonium chloride at room temperature produces a radical which is identified as Ph&sCl.
Oxidation of the square planar Rh(I) complex [Rh(SPS Me )(PPh 3 )] (SPS Me ) 1-methyl-1-P-2,6-bis... more Oxidation of the square planar Rh(I) complex [Rh(SPS Me )(PPh 3 )] (SPS Me ) 1-methyl-1-P-2,6-bis(diphenylphosphinosulfide)-3,5-(bisphenyl)-phosphinine) (1) based on mixed SPS-pincer ligand with hexachloroethane yielded the Rh(III) dichloride complex [Rh(SPS Me )(PPh 3 )Cl 2 ] (2), which was structurally characterized. The homoleptic Rh(III) complex [Rh(SPS Me ) 2 ][Cl] (4) was obtained via the stoichiometric reaction of SPS Me anion (3) with [Rh(tht) 3 Cl 3 ] (tht ) tetrahydrothiophene). Complex 4, which was characterized by X-ray diffraction, was also studied by cyclic voltammetry. Complex 4 can be reversibly reduced at E ) -1.16 V (vs SCE) to give the neutral 19-electron Rh(II) complex [Rh(SPS Me ) 2 ] (5). Accordingly, complex 5 could be synthesized via chemical reduction of 4 with zinc dust. EPR spectra of complex 5 were obtained after electrochemical or chemical reduction of 4 in THF or CH 2 Cl 2 . Hyperfine interaction with two equivalent 31 P nuclei was observed in liquid solution, while an additional coupling with a spin 1 / 2 nucleus, probably 103 Rh, was detected in frozen solution. The 31 P couplings are consistent with DFT calculations that predict a drastic increase in the axial P-S bond lengths when reducing (SPS Me ) 2 Rh(III). In the reduced complex, the unpaired electron is mainly localized in a rhodium d z 2 orbital, consistent with the g-anisotropy measured at 100 K.
Intramolecular motion in dibenzobarrelenephosphinyl radical: A single crystal EPR study at variab... more Intramolecular motion in dibenzobarrelenephosphinyl radical: A single crystal EPR study at variable temperature
The nonlinear algorithm SIMPLEX of Nelder and Mead is suitable for the minimization of a general ... more The nonlinear algorithm SIMPLEX of Nelder and Mead is suitable for the minimization of a general nonlinear function of several variables. It has been widely used for many years and appreciated for its simplicity and robustness. It does not however converge very fast.
International Journal of Radiation Applications and Instrumentation. Part C. Radiation Physics and Chemistry, 1991
X-irradiation of a single crystal of bromonitrothiazole at 77 K leads to signals in both the g = ... more X-irradiation of a single crystal of bromonitrothiazole at 77 K leads to signals in both the g = 4 and the g = 2 regions of the ESR spectrum. The angular dependence of these signals is consistent with the formation of a radical pair which exhibits hyperfine structure with a 1 H and 14 N ...
Journal of Physics E: Scientific Instruments, 1977
A description is given of a device which allows the precise orientation of a single crystal in an... more A description is given of a device which allows the precise orientation of a single crystal in any given direction with respect to the static magnetic field. It particularly facilitates the ESR analysis as it gives the angular dependence of the ESR signals in the principal planes.
ABSTRACT In addition to the formation of Ph3Sn.;, X-irradiation at room temperature of tetrapheny... more ABSTRACT In addition to the formation of Ph3Sn.;, X-irradiation at room temperature of tetraphenyltin single crystals results in the trapping of a second tin-centred radical. The g tensor and the 117Sn/119Sn hyperfine coupling tensors are shown to be consistent with the identification of Ph5Sn.. A reaction mechanisms is suggested.
The paper shows the possibilities of the complementary use of the density matrix formalism for th... more The paper shows the possibilities of the complementary use of the density matrix formalism for the simulation of the anisotropic EPR spectra and the DFT potential energy surface calculations to obtain a detailed picture of the motions of radical molecules. The combined approach is illustrated by a comparative EPR study of three phosphorus derivatives of barrelene. Three compounds were chosen as the model molecules for the observation of different temperature depend-ent dynamics of radical fragment. Each molecule based on the same barrelene skeleton has a different set of substitu-ents which by influencing the local chemical environment are likely to modify the internal dynamics. The temperature dependent EPR spectra are simulated by means of the density matrix formalism and the geometry of radicals are calcu-lated with DFT. The motion is described in terms of rotational barriers, DFT calculated energy profiles and hypotheti-cal intramolecular distortions. These two approaches lead t...
La spectroscopie de résonance paramagnétique électronique permet d'accéder à des informations... more La spectroscopie de résonance paramagnétique électronique permet d'accéder à des informations sur l'interaction des moments magnétiques électroniques (spins) avec le champ magnétique appliqué (effet Zeeman) et avec les moments magnétiques nucléaires des noyaux voisins (interactions hyperfines). Si l'on dispose d'un modèle mathématique pour simuler des spectres de RPE de poudre par le calcul, les spectres de poudre expérimentaux permettent de déduire des paramètres spectroscopiques. Dans ce but, on minimise la somme des carrés des écarts entre les valeurs échantillonnées des signaux observé et calculé. La différentiation automatique combinée à la double précision permet de faire converger la minimisation en un petit nombre d'itérations.
Journal of the Chemical Society, Faraday Transactions, 1995
Bis(N-methylimidazolidinethi-2-one)copper(I) chloride has been synthesized and its crystal struct... more Bis(N-methylimidazolidinethi-2-one)copper(I) chloride has been synthesized and its crystal structure determined. X-Irradiation of a single crystal of this compound leads to the formation of a CuII complex which was studied by EPR: it was shown that this species results from the addition of a radiogenic Cl atom on the CuI precursor. The structural changes induced by this reaction are revealed by the g-tensor and by the hyperfine tensors of one copper and two chlorine nuclei. The structure of this S2Cl2Cu type complex was compared with other sulfur- or chlorine-containing CuII complexes.
Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases, 1988
ABSTRACT The crystal structure of the title phosphated sugar (I) has been determined. The angular... more ABSTRACT The crystal structure of the title phosphated sugar (I) has been determined. The angular variations of the e.s.r. spectra obtained with a single crystal of (I) X-irradiated at T≈ 100 K have been analysed. They show that a radical pair is produced by irradiation and that a component of this pair is a phosphoryl radical. The orientations of the e.s.r. tensors are compared with the crystallographic bond directions and the role of the irradiation conditions on pair formation is examined. It appears that the phosphoryl radical is probably produced by electron capture by the cationic species [(RO)3PO]+.
Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases, 1987
ABSTRACT Single crystals of 1,2-o-isopropylidene-3,5-o-phenoxyphosphoryl-α-D-xylofuranose have be... more ABSTRACT Single crystals of 1,2-o-isopropylidene-3,5-o-phenoxyphosphoryl-α-D-xylofuranose have been X-irradiated at low temperature (ca. 77 K) and studied by e.s.r. spectroscopy. The angular dependence of the signals has led to the identification of four radicals: a phosphoranyl-type radical, two phosphonyl species and a radical pair, one of whose components is a phosphonyl-type radical. The 31P-hyperfine tensor has been obtained for each species and the pair has been characterized by its electron–electron dipolar interaction. It is shown that electron capture by a PO bond and homolytic scission of the various P—O bonds are involved in the radiation damage process.
X-irradiation of single crystals of triphenylmethylarsonium chloride at room temperature produces... more X-irradiation of single crystals of triphenylmethylarsonium chloride at room temperature produces a radical which is identified as Ph&sCl.
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