Synthesis,Structure and Catalytic Activity of a Manganese(Ⅲ) Complex Based on 2-(2-Hydroxyphenyl)-5,6-dichlorobenzimidazole Ligands

A new ligand, 2-(2-hydroxyphenyl)-5,6-dichlorobenzimidazole, H2pbmCl2(1), and a novel MnIII complex, [MnIII(HpbmCl2)(pbmCl2)(DMF)2](2),(DMF = N,N-dimethylformamide), have been synthesized and characterized. The crystal of compound 1(C13H8Cl2N2O, Mr = 279.12) belongs to the monoclinic system, space group P21 with a = 3.770(5), b = 25.20(3), c = 5.865(7) , = 92.727(17)o, V = 556.6(12) 3, Z = 2, Dc = 1.665 g/cm3, S = 1.137, μ= 0.568 mm-1, F(000) = 284, the final R = 0.0876 and wR = 0.2334 for 1848 independent reflections. The molecule is planar due to the presence of a strong intramolecular hydrogen bond between O–H group of phenol and N atom of imidazole. H2pbmCl2(1) molecules are arranged into a one-dimensional linear chain through intermolecular hydrogen bonds(N–H···O and C–H···Cl). The crystal of complex 2(C32H27Cl4MnN6O4, Mr = 756.34) belongs to the monoclinic system, space group P21/c with a = 19.043(10), b = 10.808(5), c = 18.704(11), = 115.540(6)o, V = 3473(3) 3, Z = 4, Dc = 1.446 g/cm3, S = 1.3, μ = 0.733 mm-1, F(000) = 1544, the final R = 0.1219 and wR = 0.2681 for 7811 independent reflections. The Mn ion adopts a distorted octahedral geometry coordinated by two deprotonated H2pbmCl2 ligands and two DMF molecules. The [MnIII(HpbmCl2)(pbmCl2)(DMF)2] molecules are arranged into a three-dimensional structure through hydrogen bonds(N–H···N, C–H···N and C–H···Cl) and weak π···πinteractions. The activity measurements suggest that complex 2 is able to serve as a catalyst for H2O2 disproportionation reaction to form O2 in neutral water solution.