Synthesis, structural characterization, bio-activity, and density functional theory calculation on Cu(II) complexes with hydrazone-based Schiff base ligands

Three new copper(II) complexes 1-3 of Schiff base ligands HL1 (2-hydroxybenzaldehyde2-(2-oxo-1,2-diphenylethylidene)hydrazone), HL2 (4-hydroxybenzaldehyde2-(2-oxo-1,2-diphenylethylidene)hydrazone) and L-3 (2-methoxybenzaldehyde2-(2-oxo-1,2-diphenylethylidene)hydrazone) were synthesized from methanolic medium. The complexes were characterized by elemental analyses, spectroscopic methods, magnetic susceptibility measurements, and density functional theory (DFT) studies. The synthesized ligands were characterized structurally by single-crystal X-ray diffraction studies. The optimized structure of the complexes was ascertained by DFT studies. The DNA binding ability of the complexes with calf thymus DNA (CT-DNA) was studied by UV-Vis absorption and fluorescence emission spectral studies. Absorption spectral studies revealed a hyperchromic effect and suggested the possible mode of interaction with CT-DNA. The competitive binding studies using ethidium bromide (EB) show that the complexes can replace DNA from DNA-EB adduct and suggests that the complexes probably bind to CT-DNA in intercalative mode. In vitro antibacterial activity of the complexes against Gram-negative bacteria Klebsiella pneu. moniae (K. pneumoniae), Escherichia coli (E. coli), and Shigella boydii (S. boydii), and gram-positive bacteria Staphy. lococcus aureus (S. aureus) exhibited an appreciable antibacterial activity of complex 2 against K. pneumoniae and S. boydii, but complexes 1 and 3 did not show any significant antibacterial activity. CCDC: 2084165, HL1; 2084166, HL2; 2084164, L-3.