Design, synthesis, and characterization of a series of biologically active copper(II) Schiff-base coordination compounds

Four Schiff-base copper(II) complexes, [Cu(L-1)(Phen)(H2O)](NO3)(2) (1), [Cu(L-1)(bipy)(H2O)] (ClO4)(H2O)(NO3) (2), [Cu(L-1)(Dien)](ClO4)(2)(H2O) (3), and [Cu(L-1)(ImH)(H2O)](ClO4) (4) (L-1 = N-[(1)-pyridin-2-ylmethylidene]benzohydrazide, Phen = 1,10-phenanthroline, bipy = 2, 2'-bipyridine, Dien = diethylenetriamine, ImH = imidazole), have been synthesized and characterized using various physico-chemical techniques. L-1 is coordinated to copper(II) neutral and uninegatively charged tridentate chelating agent via the azomethine nitrogen, pyridine nitrogen, and carbonyl oxygen. The copper(II) complexes are paramagnetic with octahedral stereochemistry. The crystal structures of the complexes reveal the presence of structure consisting of a tridentate N, N, O donor Schiff base, tridentate NNN donor polyamine or N, N donor heterocyclic base and the copper(II) center. In 1, 2, and 4, water is present as a coordinating molecule whereas in 2 and 4 it is also present as lattice water. In discrete monomeric species all complexes show significant hydrogen-bonding interactions. H-bridges are also present in the solid state structure. Complexes 1-4 effectively catalyze the dismutation of superoxide (O-2(-)) in alkaline nitro blue tetrazolium assay and IC50 values were determined. The susceptibility of certain strains of bacteria toward the precursors L-1 and their complexes were also evaluated.