Maurice L'Her

Redox behaviour of the dicobalt cofacial porphyrin Co2FTF4 and related complexes adsorbed on graphite electrodes

Abstract Adsorbed on graphite electrodes, Co 2 FTF4 in a potent catalyst for O 2 reduction by a four-electron mechanism. The two observable redox surface waves have been previously assigned to the two cobalt centres. Using differential pulse polarography (DPP), the behaviour of this dicobalt cofacial dimer was re-examined at different pH values in aqueous solutions and in the presence of potential axial ligands for cobalt. From these observations and from a comparison with other adsorbed porphyrins it can be concluded that (a) the porphyrins are probably adsorbed by strong interactions between graphite and the aromatic rings, and (b) the more negative surface wave is cobalt-based but the more positive one is instead a porphyrin ring oxidation. This implies that the catalyst is in the Co II Co III FTF4 state when catalytic oxygen reduction begins.

Electrocatalysis of nitrous oxide reduction: Comparison of several porphyrins and binary “face-to-face” porphyrins

Abstract The activity of several binary or “face-to-face” metalloporphyrins as electrocatalysts for reduction of nitrous oxide have been compared. It is found that a rate enhancement due to binuclear catalysis can be masked by increases in activity attributable to changes in functionality at the porphyrin periphery. By choosing systems were the peripheral substituents are inert hydrocarbons, the “face-to-face” binuclear arrangement is seen to account for at least a thousandfold increase in overall rate.

Photogeneration of charges in poly(N-vinylcarbazole) doped with lutetium bisphthalocyanines and lutetium bisnaphthalocyanines

Lutetium bisphthalocyanines and bisnaphthalocyanines, sandwich complexes having interesting electronic properties were studied as electron-acceptors associated with the donor polyvinylcarbazole (PVCz) in single-layer photoconductors. It is known, from their redox properties, that these lanthanide complexes are potential electron-acceptors as well as electron-donors; moreover, they strongly absorb light from the near-UV to the near-IR. The xerographic spectra recorded between 400 and 900 nm show that the polymeric phases doped with the lutetium bisphthalocyanines are photoconductive. These new photoconducting phases are active in the near IR domain which is promising with regard to their potential applications.

Synthesis and characterization of a novel lutetium(III) triple-decker sandwich compound: a tris(1,2-naphthalocyaninato) complex

The triple-decker sandwich complex tris(1,2-naphthalocyaninato)dilutetium(III) has been prepared in good yield, and characterized by mass spectroscopy, UV-VIS spectroscopy and electrochemistry.

Electrochemical generation of a new type of dioxygen carrier complex. Reversible fixation of dioxygen by the highly electron-deficient two-electron oxidized derivative of a dicobalt face-to-face diporphyrin

The two-electron oxidized form of the dicobalt(II) face-to-face porphyrin dimer Co2FTF4, electrogenerated in strictly anhydrous conditions, reversibly binds dioxygen.

Solvatation dans les melanges eau+carbonate d'ethylene A 40°C et comparaison aux melanges eau+ carbonate de propylene

Abstract We have evaluated for iodine, silver(I), chloride, bromide, iodide and triiodide, the activity coefficients for the transfer from water to its mixtures with ethylene carbonate at 40°C. The determination of the transfer parameters for ionic species is based on the Strehlow hypothesis relative to the ferrocene-ferricinium system. The results obtained allow us to confirm that: the silver(I) cation is more solvated by water than by ethylene carbonate; the anions which are hydrogen bond acceptors (Cl − , Br − , I − ) are more solvated by water than by ethylene carbonate and its aqueous mixtures; the affinity of the iodine molecule and the triiodide ion, which are large and polarizable species, is greater for ethylene carbonate and its aqueous mixtures than for water. In addition, this study and the comparison with water+propylene carbonate mixtures confirm the anomalous behaviour of these last media close to the miscibility gap.

Dioxygen fixation by a mixed-valence dicobalt cofacial porphyrin

A mixed-valence CoIICoIII compound is obtained by electrochemical oxidation of a dicobalt(II) cofacial dimeric porphyrin; unexpectedly, this compound reacts instantaneously with oxygen, even in the absence of an axial ligand on the cobalt(II), leading to a µ-superoxo dicobalt complex.