The oxidation of cyclohexane by photoexcited (nBu4N)4W10O32 has been investigated in the presence of iron meso-tetraarylporphyrins bearing different substituents in the β-pyrrole positions and/or in the meso-aryl groups. Irradiation at 325 nm leads to the reduction of the polyoxotungstate with the simultaneous oxidation of cyclohexane to cyclohexyl radicals which can be detected by the ESR spin trapping technique. In oxygen-free solutions, the photoreduced polyoxotungstate is able to transfer one electron to the Fe(III)porphyrin to give the ferrous complex. The subsequent reaction between this species and cyclohexyl radicals leads to the formation of σ-alkyl- Fe(III)porphyrin complexes, as demonstrated by UV-VIS and NMR spectroscopy. In the presence of oxygen, the photoreduced polyoxotungstate has the role of initiating the activation of O2 through its reduction to O2 and H2O2. As a consequence, cyclohexane is converted to cyclohexanone and cyclohexanol in a cyclic way. The Fe(III)porp...
Photocatalytic oxidation of cyclohexane by (nBu4N)4W10O32/Fe(III) porphyrins integrated systems
MALDOTTI, Andrea;MOLINARI, Alessandra;BERGAMINI, Paola;AMADELLI, Rossano;
1996
Abstract
The oxidation of cyclohexane by photoexcited (nBu4N)4W10O32 has been investigated in the presence of iron meso-tetraarylporphyrins bearing different substituents in the β-pyrrole positions and/or in the meso-aryl groups. Irradiation at 325 nm leads to the reduction of the polyoxotungstate with the simultaneous oxidation of cyclohexane to cyclohexyl radicals which can be detected by the ESR spin trapping technique. In oxygen-free solutions, the photoreduced polyoxotungstate is able to transfer one electron to the Fe(III)porphyrin to give the ferrous complex. The subsequent reaction between this species and cyclohexyl radicals leads to the formation of σ-alkyl- Fe(III)porphyrin complexes, as demonstrated by UV-VIS and NMR spectroscopy. In the presence of oxygen, the photoreduced polyoxotungstate has the role of initiating the activation of O2 through its reduction to O2 and H2O2. As a consequence, cyclohexane is converted to cyclohexanone and cyclohexanol in a cyclic way. The Fe(III)porp...I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
