Mn(II) complexes of a tridentate benzimidazole ligand: Synthesis, structural characterisation and catalase mimetic studies

Abstract

An N-butyl derivative of 2,6-bis(1-butyl-1H-benzo[d]imidazol-2-yl)pyridine was used to prepare a series of five manganese(II) complexes, which were characterised by spectroscopic and analytical methods. The molecular structures of the complexes were determined by single crystal X-ray crystallography. The complexes contain five, six or seven-coordinate manganese(II) ions, depending on the counter ions. The complexes [Mn(L)Cl2] and [Mn(L)(NCS)2] have five-coordinate manganese centres, while [Mn(L)2](ClO4)2 is six-coordinate. In [Mn(L)(NO3)2], both nitrate ions behave as bidentate chelating ligands, resulting in a seven-coordinate complex. The N-butyl benzimidazole ligand is tridentate in all the complexes. All of the complexes are active catalase mimics and [Mn(L)Cl2] is the most efficient catalyst for the disproportion hydrogen peroxide, with a turnover number of 68s−1.