Electron Transfer Reaction of Oxo(salen)chromium(V) Ion with Anilines

Abstract

The kinetics of oxidation of 16 meta-, ortho-, and para-substituted anilines with nine oxo(salen)chromium(V) ions have been studied by spectrophotometric, ESIMS, and EPR techniques. During the course of the reaction, two new peaks with lambda(max) at 470 and 730 nm appear in the absorption spectrum, and these peaks are due to the formation of emeraldine forms of oligomers of aniline supported by the ESIMS peaks with m/z values 274 and 365 (for the trimer and tetramer of aniline). The rate of the reaction is highly sensitive to the change of substituents in the aryl moiety of aniline and in the salen ligand of chromium(V) complexes. Application of the Hammett equation to analyze kinetic data yields a rho value of -3.8 for the substituent variation in aniline and +2.2 for the substituent variation in the salen ligand of the metal complex. On the basis of the spectral, kinetic, and product analysis studies, a mechanism involving an electron transfer from the nitrogen of aniline to the metal complex in the rate controlling step has been proposed. The Marcus equation has been successfully applied to this system, and the calculated values are compliant with the measured values.

A paradigm shift in rate determining step from single electron transfer between phenylsulfinylacetic acids and iron(III) polypyridyl complexes to nucleophilic attack of water to the produced sulfoxide radical cation: a non‐linear Hammett

“…From these ρ values it is clear that the accelerating effect shown by the electron releasing groups (ERG) is significantly higher than that of the electron withdrawing groups. Such type of high ρ À value is already reported in electron transfer reaction between anilines and oxo(salen)-chromium(V) (ρ = À3.8), [29] sulfoxidation of thioanisoles by Ce IV (ρ = À3.3) [30] and polypyridyl complexes (ρ = À3.2) [31] and the reactions of oxygen atom transfer from aryl sulfoxides to alkyl sulfides catalysed by rhenium(V) monoxo complex (ρ = À4.6).…”

Antipyrilquinoneimine dye formation by coupling aniline derivatives with 4-aminoantipyrine in the presence of ruthenium nanoparticles

“…However, the dye formation reaction does not proceed in the basic medium. In the acidic medium, anilines are protonated to anilinium ion in which the para position is activated [20]. Further reaction with 4-AAP at the para position leads to the dye formation.…”

Oxidation of methionines by oxochromium(V) cations: A kinetic and spectral study

“…In our laboratory, we have demonstrated that the oxidation of organic sulfides by oxo(salen)chromium(V) ions proceed through an oxygen atom transfer mechanism [53][54][55]. However Cr(V)-salen complexes undergo an electron transfer with anilines to produce oligomers [56]. In the present study we have studied the oxidation of four methionines with six oxo(salen)chromium(V) complexes as a biomimetics for the chromium-peptide complex that are formed in vivo from the reduction of Cr(VI) with biological reductants, by spectrophotometric, ESI-MS, EPR and GC-MS to determine the active species of oxidant, in aqueous media under biological pH and to arrive at a plausible mechanism.…”