Di(phenoxo)-bridged Dinuclear Mn2(II,II) and Mn2(II,III) Complexes of Macrocyclic Ligands: Structure, Properties, and Catalase-Like Function

Article abstract of DOI:10.1246/bcsj.68.1105

Dinuclear Mn2(II,II) complexes m,n)(RCOO)2> ((m,n)=(2,3), (2,4), (3,3); R=CH3, C6H5) have been prepared where (L^m,n)^2- denotes dinucleating macrocycles with two 2,6-bis(iminomethyl)-4-methylphenolate entities combined through two lateral chains, -(CH2)_m- and -(CH2)_n-, at the imino nitrogens.The complex 3,3)(CH3COO)2> crystallizes in the monoclinic space group P2₁/n with a=18.795(5), b=7.608(2), c=10.081(1) Angstroem, β=92.89(2) deg, V=1439.7 Angstroem³, and Z=2.The refinement converges with R=6.38 and R_w=9.63percent based on 2727 reflections with <*>F_o<*>>/=3?(<*>F_o<*>).A pair of Mn(II) ions are bridged by the two phenolic oxygens with a Mn-Mn separation of 3.367(1) Angstroem.An acetate group coordinates bidentately to each Mn(II) to afford a six-coordinate geometry about the metal ion.The oxidation of 3,3)(CH3COO)2> with Br2 forms a mixed-valence Mn2(II,III) complex 3,3)(CH3COO)Br2>*H2O.The Mn2(II,II) and Mn2(II,III) complexes show catalytic activity for decomposing H2O2 in DMF or DMSO.The involvement of the Mn2(II,III)/Mn2(II,IV) cycle in the catalytic process is inferred based on visible and ESR spectroscopic studies of the reaction mixture.