| Abstrakt: |
A dinuclear manganese(II) complex [Mn2L4,4(O2CMe)2] has been prepared and its structure, properties and catalase-like function studied in comparison with the analogous [Mn2Lm,n(O2 CMe)2] [m,n = 2,3; 2,4; or 3,3; (Lm,n)2- denotes macrocycles containing two 2,6-bis(iminomethyl)-4-methylphenolate entities bridged through two lateral chains, (CH2)m and (CH2)n, at the imino nitrogens]. In the centrosymmetric [Mn2L4,4(O2CMe)2] a pair of manganese(II) ions are bridged by two phenolic oxygens of (L4,4)2- in the equatorial plane and by two acetate groups at the axial sites. The configuration about each Mn is pseudo-octahedral. The Mn · · · Mn separation is 2.978(1) Å. Cryomagnetic studies (4.2–300 K) indicated a significantly strong antiferromagnetic interaction (J = -5.0 cm-1 based on H = -2JS1S 2). The complex is oxidized at +0.35 V (vs. saturated calomel electrode) at a platinum electrode to a Mn2II,III complex. It catalyses the disproportionation of hydrogen peroxide in aqueous dimethylformamide. Based on ESR and visible spectroscopic studies, a catalytic mechanism involving the interconversion between MnIIMnIII(OH) and MnIIMnIV(&z.dbd;O) species is proposed. |
