Synthesis, crystal structure and characterization of zinc(II) complexes with the tripod ligand tris(2-benzimidazolylmethyl)amine and ,β-unsaturated carboxylates

Abstract

Four 5-coordinate zinc complexes containing the tripod ligand, tris(2-benzimidazolylmethyl)amine (ntb), and four different α,β-unsaturated carboxylates (L1–4), with compositions [Zn(ntb)(L1–4)](NO3)·nH2O (L1 = acrylate; L2 = α-methacrylate; L3 = trans-cinnamate; L4 = 2-hydroxycinnamate; n = 1, 1.5 and 2), were synthesized and characterized by means of elemental analyses, electrical conductivities, thermal analyses, i.r., u.v., and 1H-n.m.r. spectra. The novel crystal structure of [Zn(ntb)(L3)](NO3)·H2O·DMF has been determined by a single-crystal X-ray diffraction method, and shows that each zinc ion is linked to a tris(2-benzimidazolymethyl)amine (ntb) unit and a trans-cinnamate. The zinc ion is 5-coordinate with a N4O ligand set. The coordination geometries of the zinc ion may be best described as a distorted trigonal bipyramid of site symmetry C3.