Synthesis, crystal structure and antimicrobial properties of a copper(II) complex of an unsymmetrical tripodal ligand

A new copper(II) complex of an unsymmetrical tripodal ligand (NN(2)O222) derived from tris(2-aminoethylamine) amine (tren) by substitution of one aminoethyl group by an hydroxyethyl group has been synthesized and characterized by X-ray crystallographic methods as [(NN(2)O222)Cu(ImH)](ClO4)(2)center dot 0.5H(2)O(NN(2)O222=2-[bis(2-aminoethyl) amino] ethanol; ImH=imidazole). Crystals of the complex are orthorhombic, space group Pna2(1), with a=29.983(10), b=15.568(5), c=8.127(3) angstrom. Two similar monometallic cations exist in the asymmetric unit and in each case the Cu(II) ion is five-coordinate with tetragonally distorted trigonal bipyramidal geometry. Variable-temperature magnetic measurements show that there is very weak antiferromagnetic interaction between the metal ions. Cyclic voltammetry indicates quasi-reversible Cu-II/Cu-I redox behavior at +44 mV vs SCE. An antimicrobial activity study found that the complex is active against Candida albican, Staphylococcus aureus, Bacillus pumilus, Klebosiella pneumoniae and Escherichia coli, but to no greater extent than Cu(ClO4)(2)center dot 6H(2)O.