Coordination number in copper(II) complexes with bipyridine-dicarboxylate anion and diamine derivatives

Mononuclear copper(II) compounds have been prepared by the treatment of CuCl2 2H(2)O and 2,2-bipyridine-4,4-dicarboxylic acid (bpdcH(2)) with 1,3-diaminopropane (dap) or ethylenediamine (en). The compounds were characterized by IR, UV-Vis spectroscopy and X-ray crystallography. Studying the structure of [Cu(bpdc)(dap)(H2O)] 2H(2)O (1) shows that the complex is a five-coordinate [CuN4O] system, with a Cu-O-aqua distance of 2.204(6)angstrom, whereas the structure of [Cu(bpdc)(en)(H2O)(2)] 4H(2)O (2) is a distorted octahedral environment around the copper(II) [CuN4O2] with Cu-O-aqua distances of 2.419(4) and 2.658(4)angstrom. This deviation was compared with similar copper(II) complexes. In addition, theoretical configurations of the title compounds were relaxed and studied in terms of the combined analysis of HOMO-LUMO energy gap, molecular electrostatic potential, Frontier molecular orbital and quantum molecular descriptors.