F.X. Sauvage

A Laser Photolysis Study of Triplet Lifetimes and of Triplet–Triplet Annihilation Reactions of Phthalocyanins in DMSO Solutions(Etude des Durées de Vie du Triplet et des Réactions d'Annihilation Triplet–Triplet de Phthalocyanines dans le DMSO par Photolyse Laser)

Triplet decay of Mg and Zn phthalocyanins have been studied by laser flash photolysis as a function of concentration. The triplet decay mechanism changes from a near first order in dilute solution to an almost second order in concentrated solutions. This is interpreted in terms of triplet–triplet recombinaison. With the help of a reducing agent, it is shown that the triplet–triplet reaction can lead to charge separation.

Linearly extended tetrathiafulvalene analogues with fused thiophene units as π-conjugated spacers

A new series of linearly extended tetrathiafulvalene analogues with thienothiophene and dithienothiophene π-conjugating spacers has been synthesized. Electronic absorption spectra present a vibronic fine structure typical for rigid conjugated systems. Investigation of the electrochemical behaviour of the new donors by cyclic voltammetry reveals the successive generation of stable radical cation and dication species. The crystallographic structure of a single crystal of a dication salt of TT-TTF(ClO4)2 has been analysed by X-ray diffraction. The dication presents a syn conformation stabilised by S⋯S intramolecular interactions. The quinoid structure expected for the spacer for the +2 oxidation state is clearly revealed by the bond lengths.

Effects of Structural Factors on the π‐Dimerization and/or Disproportionation of the Cation Radical of Extended TTF Containing Thiophene‐Based π‐Conjugated Spacers

The electrochemical and chemical oxidation of extended TTF 4 and 5 are analysed by cyclic voltammetry, Visible/NIR and ESR spectroscopies, and the X-ray structures of the new salts 5 x BF(4)(CH(2)Cl(2)) and 4 x ClO(4)(THF)(1/2) are presented. The effects of structural factors on the pi-dimerization or the disproportionation reaction of the cation radical are shown. The oxidation of compound 4 presents the successive formation of stable cation radical and dication species both in dichloromethane (DCM) and in a CH(3)CN/THF mixture. In contrast, for compound 5, the stability of the oxidation states strongly depends on the nature of the solvent. In DCM, the oxidation of 5 proceeds by two close one-electron transfers while in CH(3)CN/THF the dication is directly formed via a two-electron process. The X-ray structures of the two salts reveal the formation of pi-dimers of cation radical. While the dimer (5(2))(2+) is due mainly to pi-pi interactions between the conjugating spacer, the multiplication of the sulfur atoms in compound 4 contributes to stabilize the dimer by the combined effects of S-S and pi-pi interactions. Visible/NIR and ESR experiments confirm the higher tendency of 4(+)(.) to dimerize with the occurrence of dimer and monomer in solution, while for 5(+)(.) only the monomer is detected in DCM. On the other hand, by dissolution of 5 x BF(4)(CH(2)Cl(2)) in CH(3)CN, only the neutral and the dicationic states of compounds 5 are observed owing to the disproportionation reaction.

Synthesis, Spectroscopic, and Electrochemical Characterization of a Schiff Base: 4,4′-bis[(4- diethylaminosalicylaldehyde)diphenyl methane]diimine and Its Complexes With Copper(II), Cobalt(II), and Cadmium(II)

The synthesis of a new ligand tetradentate Schiff base: 4,4′-bis[(4-diethyl aminosalicylaldehyde) diphenyl methane] diimine (H2L), obtained by condensation of 4,4′-diaminodiphenyl methane with 4-diethylaminosalicylaldehyde, and its complexes with copper(II), cobalt(II) and cadmium(II), is described. The metal complexes were characterized by elemental analysis, by UV-visible, infrared, and EPR spectroscopy, by cyclic voltammetry, and by thermal analysis (DTA-TG). The coordination of the metal ions to the ligand occurs through the N2O2 system. Thermal studies indicate that the ligand is more stable than the metal complexes (up to 310°C).

Interaction of light with Na+ C222.Na−. A laser flash photolysis and EPR investigation

Abstract Illumination of dry films of Na + C222.Na − by a 15 ns laser pulse at 605 nm, causes bleaching of the absorbance of Na − at 650 nm while a new absorbing species is formed in the near infrared. This process is partially reversible, with a half-life of ≈ 30 ms at room temperature. The amount of bleaching depends in a non-linear way on the laser power. The appearance of a paramagnetic species during steady state illumination was detected by EPR spectroscopy.