Dinuclear Hg(II) complex of new benzimidazole-based Schiff base: one-pot synthesis, crystal structure, spectroscopy, and theoretical investigations

Abstract

A new dinuclear complex, [HgCl2L]2, was prepared using a Schiff base derived from benzimidazole (L = [1-(1H-benzo[d]imidazol-2-yl)-N-(4-methoxyphenyl)ethan-1-imine]. The mercury complex was obtained in good yield by one-pot reaction under microwave irradiation from 2-acetylbenzimidazole and p-anisidine, followed by addition of HgCl2. The Hg(II) complex has been characterized by single-crystal X-ray diffraction analysis, IR and UV-vis spectroscopy. The mercury complex is built up from a dinuclear unit related by an inversion center through two bridging chlorine atoms. Each mercury atom is coordinated by two N atoms of the Schiff base L, one terminal Cl atom and two bridging Cl atoms in a square pyramidal geometry. To support experimental data, theoretical calculations including molecular geometry, electronic transitions and vibration frequencies of the ligand and its complex in the ground state were carried out using the global hybrid (B3LYP) density functional. In addition, a qualitative description of excited states and charge transfer character of electronic transitions states were carried out by plotting the Natural Transition Orbitals (NTOs) for main states. Theoretical calculations are in good agreement with experimental values.