Intermediate species detected in oxidation reactions of FeTM(4)PyP 5+ with iodosylbenzene by EPR and UV-Vis spectroscopies

Abstract

The iron porphyrin, tetrakis (4- N-methylpyridyl) porphyrinato iron(III) perchlorate (FeTM(4)PyP 5+) was studied as a catalyst for the oxidation reaction of an organic substrate by iodosylbenzene in organic solvents. The reaction system was studied by UV-Vis and EPR spectroscopic techniques at low temperature. The following intermediate species were detected: (i) iron(III)porphyrin rhombic species in the initial step of the reaction, (ii) oxo iron(IV)porphyrin (ferryl species) detected at 540 nm in the UV-Vis spectra and (iii) iron(III) N-oxides species (FeON) by EPR with g value 4.30. The species oxo iron(IV) porphyrin π-cation radical supposed to be present in the oxidation reaction was not detected in our experimental conditions. However, there is evidence for the existence of this species due to the reaction yields observed.