Redox properties of photoexcited (nBu4N)3 PW12O40/FE(III) porphyrins composite systems

The photochemical and photocatalytic properties of (nBu4 N)3 PW12O40 (PW12O40/3-) was investigated in the presence of several Fe(III-meso-tetrarylporphyrins. The photochemical excitation of the polyoxotungstate in the presence of 2-propanol or cyclohexane leads to its reduction and simultaneous oxidation of the organic substrate. The reduced polyoxotungstate is able, in turn to transfer one electron to the Fe(III) porphyrin to give the ferrous complex. In the presence of anaerobic cyclohexane, σ-alkyl-Fe(III) complexes are obtained as a consequence of the reaction between cyclohexyl radicals and the iron porphyrin in its reduced form. Subsequent oxidative migration of the σ-bound cyclohexyl group from the iron to one of the pyrrole nitrogens leads to the formation of N- substituted porphyrin. The results obtained by laser flash photolysis experiments indicate that the electron transfer from the photoreduced polyoxotungstate to the FE(III) porphyrin complexes is faster than to O2. There...