Synthesis, spectral and electrochemical studies on Fe (III) and Mn (II) complexes with a tridentate ligand carrying pendant benzimidazolyl groups

Abstract

Mononuclear iron (III) and manganese (II) complexes with stoichiometry [Fe(BBES)X₃].nH₂O and [Mn(BBES)X₂].nH₂O have been synthesized and characterized utilizing a tridentate ligand, 1,5-bis (benzimidazol-2-yl)-3-thiapentane (BBES) with anionic ligands like Clˉ, NO₃ˉ, HCOOˉ and NCSˉ. Mossbauer data for Fe(III) complexes indicate that the isomer shift values lie in the range typically observed for high spin Fe(III) complexes while slightly large quadrupole splitting parameter indicate a rhombically distorted Fe(III) centre. Cyclic voltammetric studies for Fe(III) complexes indicate that binding of HCOOˉ anion stabilizes the Fe(III) centre whereas NO₃ˉ destabilizes it. A strong EPR signal centered at <i>g≈</i> 2 for Mn (II) complexes prove that non-cubic crystalline electric fields are weak. Zero field splitting parameter D has also been calculated.