Synthesis, characterization of binary and ternary copper(II)-semicarbazone complexes: Solvatochromic shift, dipole moments and TD-DFT calculations

Abstract

A novel semicarbazone O 2 N donor ligand, HL, was synthesized by condensation of 2-aminochromone-3-carboxaldehyde with semicarbazide hydrochloride. The HL ligand is allowed to react with several copper(II) salts namely: AcO – , NO 3– , SO 42– and Cl – , in absence and presence of secondary ligand (SCN - , 8-HQ and 1,10-phen), forming binary and ternary copper complexes. Characterization of the compounds has been done using various techniques like elemental analyses, magnetic moments, conductance measurement, thermogravimetry and FT-IR, UV-Vis, 1 H and 13 C NMR, EPR and mass spectroscopy. The HL ligand acts as monoanionic O 2 N tridentate in most complexes, forming Cu(II) complexes with an octahedral and square planar geometrical arrangements. The compounds exhibit luminescence property; promising interesting potential applications as photoactive materials. The ground state (µ g ) and excited state (µ e ) dipole moments are estimated from solvatochromic shifts of absorption and fluorescence spectra as a function of the dielectric constant (Ɛ) and refractive index (n) by using Bilot–Kawski, Lippert–Mataga, Bakhshiev, Kawski–Chamma–Viallet and Reichardt correlation methods. Excited state dipole moment is observed as larger than the ground state dipole moment. The molecular structural parameters of the ligand and its Cu(II)- complexes have been calculated on the basis of DFT level implemented in the Gaussian 09 program at the B3LYP/6-31G(d,p) level and the theoretical data are correlated with the experimental data. The antibacterial properties of the ligand and its complexes have been screened against selected kinds of bacteria and fungi.