Synthesis and characterisation of manganese(II) complexes with bis(2-benzimidazolyl)propane and bis(2-benzimidazolyl) butane

Flexible bidentate ligands 1,3-bis(2-benzimidazolyl)propane [GAB] and 1,4-b is(2-benzimidazolyl)butane [AAB] have been synthesized and a series of mang anese (II) complexes of general composition [MnL2X2].nH(2)O have been prepa red where (L = GAB, AAB) and X is an exogenous anionic ligand (X = HCOO-, C H3COO-, Cl-, SCN-). Using low temperature EPR studies, D and E parameters h ave been calculated for these complexes, which indicate a rhombic distortio n of the six co-ordinated complexes. The ligand AAB provides a larger D, E implying a greater ligand field distortion in comparison to the ligand GAB. Cyclic voltammetric results show an irreversible oxidation of Mn(II) to Mn (III) for all complexes except thr complexes [Mn(AAB)(2)(SCN)(2)] and [Mn(G AB)(2)Cl-2]. The CV data indicate that the SCN- anion tends to stabilize th e Mn(Il) oxidation state relative to the Cl-.