Synthesis, crystal structure and properties of a copper(II) complex with the tripod ligand tris(N-methylbenzimidazol-2-ylmethyl)amine and 4-hydroxycinnamate

A five-coordinate copper complex with the tripod ligand tris(N-methylbenzimidazol-2-ylmethyl)amine (Mentb) and 4-hydroxycinnamate, with the composition [Cu(Mentb)(4-hydroxycinnamate)](ClO4)center dot 0.5DMF, was synthesized and characterized by means of elemental analyses, electrical conductivities, thermal analyses, IR, and UV. The crystal structure of the copper complex has been determined by single-crystal X-ray diffraction, and shows that the Cu-II atom is bonded to a tris(N-methylbenzimidazol-2-ylmethyl)amine (Mentb) ligand and a 4-hydroxycinnamate through four N atoms and one O atom, giving a distorted trigonal-bipyramidal coordination geometry (tau = 0.78), with approximate C3 molecular symmetry. Cyclic voltammograms of the copper complex indicate a quasireversible Cu+2/Cu+ couple. Electron spin resonance data confirm the trigonal-bipyramidal structure and indicate g(parallel to) < g(perpendicular to) with a very small value of A(parallel to) (57 +/- 10-4 cm(-1)).