92186-11-3Relevant academic research and scientific papers
Electrochemistry of oxo- and peroxotitanium(IV) porphyrins. Mechanism of the two-electron reduction of a η2-coordinated peroxo ligand
Malinski, Tadeusz,Chang, Dane,Latour, Jean-Marc,Marchon, Jean-Claude,Gross, Maurice,Giraudeau, Alain,Kadish, Karl M.
, p. 3947 - 3955 (2008/10/08)
The oxidation and reduction reactions of oxotitanium(IV) tetraphenylporphyrin, TiO(TPP), peroxotitanium(IV) tetraphenylporphyrin, Ti(O2)(TPP), and peroxotitanium(IV) octaethylporphyrin, Ti(O2)(OEP), in dichloromethane were investigated by electrochemical and spectroscopic techniques. Two one-electron oxidations and two one-electron reductions of the porphyrin ring were observed for TiO(TPP). Similar oxidations were found for Ti(O2)(TPP) and Ti(O2)(OEP). In addition, the peroxo complexes showed three reduction steps. The first reduction gives a porphyrin anion radical complex, which undergoes protonation by trace water followed by internal electron transfer to give a hydroperoxotitanium(III) porphyrin complex. The latter is then reduced at the porphyrin-ring system. Finally, internal transfer of two electrons cleaves the oxygen-oxygen bond of the coordinated hydroperoxide to give the oxotitanium(IV) porphyrin complex and hydroxide ion. The overall reaction is a two-electron reduction of the peroxo ligand in an ECEC mechanism. The oxotitanium(IV) complex that is obtained can be further reduced to the anion radical and the dianion of the porphyrin ring. Possible competing processes, which result in a substoichiometric reduction of the peroxo ligand, are surveyed.
