Mixed-ligand copper complexes with unsymmetrical tridentate Schiff base ligands and 2,2′-bipyridine: Synthesis, x-ray crystallography and antibacterial properties

Three new mixed-ligand Cu(II) complexes with general formula [CuLx(2,2'-bipyridine)]ClO4 (x = 1-3) where synthesized and characterized by x-ray crystallography, elemental analyses, and spectroscopic techniques such as FTIR and UV-Vis spectroscopy. The complexes contain an unsymmetrical Schiff base ligand (L-x) and one 2,2'-bipyridine co-ligand. The Schiff base ligands are NN'O type unsymmetrical ligands which are the mono-condensed form of the reactions between meso-1,2-diphenyl-1,2-ethylenediamine with salicylaldehyde (1), 5-bromosalicylaldehyde (2) or 3-methoxysalicylaldehyde (3). Antibacterial activity of the new complexes along with their parent complexes, i.e. [CuLx(pyridine)]ClO4 (1a-3a) were studied against 2 g negative bacteria (E. Coli and K. Pneumonia) and 2 g positive bacteria (S. aureus and B. Subtilis). The complexes were almost inactive against the studied gram negative bacteria but showed very good activity against the studied gram positive ones. (C) 2019 Elsevier B.V. All rights reserved.