Synthesis, structures, and fluorescent properties of two oxalato-bridged dinuclear zinc(II) complexes with tridentate and tetradentate polybenzimidazole ligands

Abstract

Two dinuclear oxalato-bridged zinc(II) complexes, [Zn₂(bbma)₂(μ₂-η⁴-ox)](ClO₄)₂ (1) and [Zn₂(ntb)₂(μ₂-η²-ox)](ClO₄)₂·4CH₃OH (2), containing tridentate and tetradentate polybenzimidazole ligands were synthesized, where bbma is bis(benzimidazol-2-yl-methyl)amine and ntb is tris(2-benzimidazolylmethyl)amine. They were characterized by single-crystal X-ray diffraction, elemental analysis, IR, and fluorescence spectroscopy. Zinc(II) complexes in 1 and 2 are five-coordinate in distorted trigonal bipyramidal geometry. Oxalate bridges two zinc(II) ions as a bis-bidentate chelate in 1, while bis-monodentate in 2. The Zn⋯Zn distances are 5.318(1) Å for 1 and 7.1295(5) Å for 2, respectively. 1-D chain structures are formed in 2 by intermolecular hydrogen bonds. The solid state fluorescence spectra have been studied for 1 and 2.

Graphical Abstract

Keywords:

• Dinuclear zinc(II) complex
• Benzimidazole
• Oxalic acid
• Crystal structure