Synthesis, spectroscopic, structure, thermal analyses, and biological activity evaluation of new norfloxacin vanadium (V) solvates (L) (L = An, DMF, Py, Et3N and o-Tol)

Abstract

Novel five complexes of vanadium (V) with norfloxacin containing oxygen donor ligand in presence of different solvents containing nitrogen or oxygen donor ligand have been prepared as solid complexes [VO(Nor)2L]Cl3·nH2O, where L = aniline (An), dimethylformamide (DMF), pyridine (Py), o-tolidine (o-Tol), and triethylamine (Et3N). The isolated complexes have been characterized with physicochemical and spectroscopic techniques. In these complexes, norfloxacin acts as a bidentate ligand bound to the vanadium ion through the pyridone oxygen and one carboxylato oxygen. The stretching band of ν(C=O)pyridone at 1619 cm−1 of ligand shifts toward lower wavenumbers at 1519 cm−1 for DMF, at 1578 cm−1 for An, at 1574 cm−1 for Py, at 1574 cm−1 for o-Tol, and 1555 cm−1 for Et3N, which indicates the pyridone group bonding to the vanadium (V) ion. The lowest energy model structure of each complex has been proposed by using the density functional theory at the B3LYP/CEP-31G level of theory. The ligand and their metal complexes were also evaluated for their antibacterial activity against three Gram-positive—Staphylococcus aureus, Staphylococcus epidermidis, and Bacillus pumilus—and three Gram-negative —Pseudomonas aeruginosa, Escherichia coli, and Klebsiella pneumoniae—microorganisms.