New nanoparticle metal complexes based on cefaclor and 2,2′-bipyridine ligands: synthesis, characterization, DFT studies and their antimicrobial evaluation

Abstract

Five new nanoparticles mixed ligand complexes were synthesized by interacting the antibiotic cefaclor (CEF) with some metal ions such as Cr(III), Co(II), Cu(II), Zn(II) and Cd(II) with 2,2′-bipyridine (Bipy) in 1:1:1 molar ratio. The complexes were characterized by elemental analyses, thermal analyses (TG, DTG, and DTA), spectroscopic methods (FT-IR, UV-Vis, 1H NMR, and X-ray powder diffraction, or XRD), molar conductivity and magnetic moment (μeff). The molar conductance data supported that all complexes were electrolyte in nature with 1:2 for Cr(III) and 1:1 for bivalent metal ions. Magnetic moments data and electronic absorption spectra for all complexes supporting octahedral geometry for the metal complexes. Infrared data showed that CEF interacted as a tridentate ligand with metal ions via nitrogen of primary amine, one oxygen atom of carboxylate group and carbonyl group of a β-lactam ring, while, Bipy chelated through two nitrogen atoms. Optical band energy gap (Eg), the calculated values of Eg for the metal complexes confirmed they were semiconductors. CEF, Bipy, and their metal complexes underwent TG and DTG, and the decomposition mechanisms were discussed. DTA data exhibit exothermic and endothermic peaks. The average crystalline size (Cs), dislocation density (D), full width at half maximum (FWHM), and the kind of compounds (crystalline or amorphous) were determined using XRD which indicted that complexes (3), (4) and (5) were crystalline but complexes (1) and (2) were amorphous in nature. The compounds' optimal molecular geometry was determined using density functional theory (DFT) computations. All studied complexes with σ values varied from 22.222 to 44.444 eV were soft respect to CEF (σ = 16.393 eV). All compounds were tested for their antimicrobial activities against gram-positive and gram-negative strains of bacteria and fungi. The results indicated that the tested metal complexes exhibited notable effectiveness more than CEF and Bipy, of which these synthesized compounds could potentially serve as improved bactericides and fungicides.