Study by EPR and electronic spectroscopy of intermediates in iron porphyrin and iodosylbenzene reaction

Abstract

The iron tetraphenylporphyrin chloride, (FeTPP)Cl), reaction with iodosylbenzene, (PhIO), was followed in different solvents by UV/Vis spectroscopy at 213 K and EPR spectroscopy at 4.2 K. The species 1 , (Fe IV-O-Fe IV(O)P .+), a dimeric active intermediate predominates in dichloromethane; 1 was evidenced by the large EPR radical signal at g = 2.006 (6K). Species 2 , (Fe IV(O)P .+), coexists, characterized by the less intense g = 3.950 EPR signal (6K). In methanoldichloromethane the electronic spectra shows the Soret band at 422 nm and visible bands at 542 nm and 580 nm, corresponding to formation of compound 3 , (PFe IVOH). The EPR spectra shows the weak g = 3.720 signal at 6 K, indicating species 2 coexistency. Species 1 have an important role in these unhindered iron porphyrin catalysts.