Synthesis and catalase-like activity of dimanganese complexes with phthalazine-based ligands

Abstract

Dimanganese complexes Mn2 III(L1)(OAc)4 and Mn2 III(L2)(OAc)4 with the phthalazine-based ligands 1,4-di(2′-benzimidazolyl)aminophthalazine (H2L1) and 1,4-di(N-methyl-2′-benzimidazolyl)aminophthalazine (H2L2) have been prepared and characterized. The complexes accelerate the disproportionation of H2O2 into water and dioxygen in buffered aqueous solutions in a near-neutral pH range thus can be regarded as catalase models. Results of kinetic measurements indicate a similar mechanism for the two catalysts, but formation of the proposed peroxo-adduct intermediate is less favored for Mn2 III(L1)(OAc)4. It is presumed to be the reason for the lower rates for this catalyst even at higher pH.