Cu(II) complex based on lemofloxacin and N,N-donor ligand: Synthesis, crystal structure, DFT calculations, and in vitro antimicrobial evaluation

Abstract Cu(II) complex of second-generation quinolone lemofloxacin with 2,2′-bipyridylamine formulated as [Cu(lmx)(bipym)Cl](CH3OH)·3H2O (1) [lmx = lemofloxacin, bipym = 2,2′-bipyridylamine] has been synthesized and characterized utilizing X-ray single-crystal diffraction and spectroscopic methods. The crystal structure of [Cu(lmx)(bipym)Cl](CH3OH).3H2O has been determined via X-ray diffraction and the result showed that Cu (II) ion is coordinated by two oxygen atoms from lmx ligand and two nitrogen atoms from bipym ligand in a slightly distorted square pyramidal arrangement. The X-ray structural analysis shows that the complex crystallizes in the monoclinic system with a = 15.031(3), b = 14.2647(13), c = 16.687(4) A, and space group P21/n. Thermal analysis studies was used to determine the decomposition pattern of the complex, also confirm the presence of lattice water molecules and the metal oxide which is the final product. X-band electron paramagnetic resonance (EPR) spectroscopy at liquid nitrogen temperature (LNT) from solution indicates the presence of a monomeric unit in the crystal structure. The Density functional theory (DFT) studies revealed that the Cu(II) complex is a soft molecule with high chemical reactivity and low kinetic stability as indicated by the low values of the global hardness (η = 1.063), energy gap (ΔE = 2.126 eV) and chemical potential (µ = -5.304). Furthermore, the ligand and complex were also subjected to antimicrobial activity against three (3) Gram (+) and two (2) Gram (-) bacterial strains by using the agar disk diffusion method and the findings indicated that the complex possesses a better activity compared to the parent ligand lmx while a decreased antimicrobial activity was observed against E. coli.