Spectroscopic, DFT, and Antimicrobial Studies of New Synthesized Oxytetracycline Complexes

Abstract

Oxytetracycline metal complexes were synthesized with Co(II), Ni(II), Zn(II), Mn(II), Fe(III), and Cu(II). The structures of the synthesized complexes were proposed based on their infrared, UV–Vis, magnetic susceptibility, ESR for the copper complex, elemental analysis and thermal analysis (DTA, TGA and DSC). The data suggested that oxytetracycline has more than one site for chelation depending on the metal ion. From physicochemical and spectroscopic data, octahedral structures were suggested for Ni (II) and Fe(III), while Zn(II), Co(II), and Mn(II) exhibited tetrahedral geometries. Only Cu(II) exhibited square planer geometry. DFT studies confirmed the oxytetracycline binding sites, and the energy of HOMO, LUMO, and global chemical reactivity descriptors were obtained at the B3LYP/6-311G level of theory. The complexes were evaluated for antimicrobial activity, and the results showed that the tested complexes exhibited significant activity against the tested microorganisms.