Preparation and spectral characterization of 1,3-bis(1H-benzimidazol-2-yl)-propan-1-one and its various Zn(II) complexes

Abstract

A new asymmetric bis-benzimidazole ligand, 1,3-bis(1H-benzimidazol-2-yl)-propan-1-one (L), was synthesized by known methods. ZnX2 (X = Cl, Br, I, ClO4, NO3, OAc) complexes of the ligand were synthesized and characterized by elemental analysis, molar conductivity, TGA, ESI-MS, FT-IR, NMR and fluorescence spectroscopy. According to the spectral data, the ligand exhibits a keto-enol equilibrium in polar solvents. The ligand gave complexes with eight-membered chelate ring coordinating through both of the C=N nitrogen atoms, whereas the C=O oxygen atom does not bind to the Zn(II) ion. Fluorescence properties of the ligand and the complexes were investigated. Considerable red shift is observed in ZnBr2, ZnI2 and Zn(OAc)(2) complexes according to the ligand. By contrast, the Zn(OAc)(2) complex differs from the other Zn(II) complexes by thermal composition, molar conductivity and fluorescence characteristics, probably due to the coordination of the acetate oxygen atom.