UV-vis study of the reaction of chloro(tetraphenylporphyrinato)manganese(III) with tetra-n-butylammonium hydrogen monopersulfate in the presence of imidazole

Abstract

Reaction of chloro(tetraphenylporphyrinato)manganese(III) with tetra-n-butylammonium hydrogen monopersulfate (n- Bu 4 NHSO 5) in the presence of high ratio of imidazole was followed by UV-Vis spectroscopy in CH 2 Cl 2 at room temperature. The variation in the UV-vis spectra shows that the reaction goes through Mn ( III ), high valent Mn ( V ) or Mn ( IV ), Mn ( III ), low valent Mn ( II ) and again Mn ( III ) complexes. The Mn ( III ) complex before the addition of n- Bu 4 NHSO 5 could not be reduced to Mn ( II ), but Mn ( III ) complex which was obtained after decay of high valent Mn complexes was reduced to Mn ( II ), probably because its spin state is different from the first one. Addition of methanol to the reaction mixture (in the presence or absence of ferrocene) shows that two high valent Mn complexes [( Mn V ( TPP )-( O )( X )] ( X = Im - or OMe -) and [ Mn IV ( TPP )( OMe )2] are involved in the course of the reaction. Using meta-choloroperbenzoic acid instead of (n- Bu 4 NHSO 5) as oxidant showed that reduction of Mn ( III ) to Mn ( II ) is taking place only in the presence of HSO 4.