Synthesis and spectral characterization of 1,3-bis-(1H-benzimidazol-2-yl)-2-oxapropane complexes with various Zn(II) salts

Abstract

1,3-Bis(1H-benzimidazol-2-yl)-2-oxapropane (L) complexes with ZnX2 (X = Cl-, Br-, I-, CH3COO-, NO3-, ClO4-) (1-6) were synthesized and characterized by elemental analysis, molar conductivity, TGA, FT-IR, NMR, ESI-MS and fluorescence spectroscopy. In addition, the crystal structure of [1,3-bis(1H-benzimidazol-2-yl)-2-oxapropane-kappa N-2,N']dibromozinc(II) {2, [Zn(L)Br-2]}, is reported. The Zn(II) ion has a tetrahedral environment in the chelate complex. The ZnCl2 complex (1) is structurally different from the others: It shows a broad signal at 7.28 ppm in the H-1 NMR spectra assigned to two coordinated water molecules. The very low solubility of the acetate complex (4) leads us to suggest a polymeric structure with [Zn-2(mu-OAc)(4)(L)(2)](n) paddlewheel units. The ligand shows from two to four emission bands in polar solvents. Compared to the ligand, the complexes show weak fluorescence intensity in ethanol and exhibit red-or blue-shift. (C) 2014 Elsevier B.V. All rights reserved.