Crystal structure, spectroscopic, DFT calculations and antimicrobial study of the Cu(II) complex bearing second-generation quinolone ofloxacin and 2,2′-bipyridine

Abstract

Cu(II) complex of second-generation quinolone ofloxacin with 2,2′-bipyridine formulated as [Cu(ofx)(2bpy)(H2O)].ClO4·2H2O (1) [ofx = ofloxacin, 2bpy = 2,2′-bipyridine] has been synthesized. The coordination possibility of the ofx and 2bpy towards metal ion was proposed using single-crystal X-ray diffraction analysis (SCXRD), IR, UV–Visible, EPR, thermal analysis, molar conductance, and elemental analysis. The interaction of Cu(II) with the deprotonated ofloxacin ligand resulted in the formation of the mononuclear complex of the type [Cu(ofx)(2bpy)(H2O)].ClO4·2H2O. Single crystal X-ray crystallography data revealed a five-coordinate, distorted square-pyramidal arrangement in the complex. The complex crystallizes in the triclinic system with a = 10.2192(13), b = 12.7080(19), c = 12.8156(16) Å, and space group P–1. The measurement of the complex molar conductance in DMSO (10−3 M solution at 25 °C) revealed the electrolytic nature of the complex and was of the 1:1 type. The presence of coordinated water molecules and the metal oxide in the final product was determined by thermal analysis studies. DFT calculations were carried out for the complex ion and the two ligands using the B3LYP/631-G(d) level of theory and the HOMO-LUMO energy gap was evaluated. The results showed that the complex with the lowest energy gap value (0.951 eV) is more reactive than the ligands. The ligand and its copper (II) complex were screened in order to evaluate the antimicrobial activity by measuring the inhibition zone (mm). The results showed that the metal complex was observed to be more active than the parent ligand.