Syntheses, solvatochromism, and antimicrobial activities of new binuclear copper(II) mixed-ligand complexes in a ternary system with β-diketones and diamine ligands

Ternary complexes of binuclear copper(II) nitrate with bis(beta-diketones) [beta-diketones = 2-phenyl-1,3-bis-(tetraacetyl-propane), L-1, or 2-(o-hydroxyphenyl-1,3-bis-(tetraacetyl-propane), L-2] and diamines [diamines = N,N,N',N'-tetramethylethylenediamine (tmen), 2,2'-bipyidine (bipy) and 1,10-phenanthroline (phen)] have been synthesized, where NO3- groups are counter or coordinated anions. The structures of the complexes and their solvatochromic behavior were investigated by elemental analysis, spectroscopic, magnetic, molar conductance, and thermal analysis. Solvatochromism was observed for only three complexes where they displayed a drastic color change with increasing donor strength of the solvent. This behavior is due to the solute-solvent interaction between the chelate cation and the solvent. Spectroscopic studies of the complexes implicate tetragonal distortions in strongly polar solvents and square planar or square pyramidal geometries in the presence of weakly coordinating molecules. Biological studies of the ligands and their complexes showed a significant inhibition on the growth of selected Gram-positive bacteria and moderate effect against two kinds of Gram-negative bacteria as well as one kind of pathogenic fungi.