Synthesis, spectroscopic characterization, thermal stability and biological studies of mixed ligand complexes of gemifloxacin drug and 2,2'-bipyridine with some transition metals

The mixed ligand Zn(II), Zr(IV), Pd(II), Ce(IV), Th(IV), and U(VI) complexes of gemifloxacin and N-donor 2,2'-bipyridine have been prepared. These complexes have been characterized by elemental, infrared (IR), ultraviolet-visible (UV-Vis), H-1 nuclear magnetic resonance (NMR), mass spectroscopy, thermal, molar conductance and magnetic susceptibility analyses. The infrared spectra indicate that gemifloxacin acts as a bidentate deprotonated ligand bound to the metal through the pyridone oxygen and one carboxylate oxygen, whereas the 2,2'-bipyridine coordinates through the two nitrogen atoms. The central metal in each complex is six-coordinate and a slightly distorted octahedral geometry is proposed. The calculated bond length and force constant, F(U=O), in the uranyl complex are 1.751 and 641.04 N m(-1), respectively. The thermodynamic parameters are calculated from the thermal analysis curves using the Coats-Redfern and Horowitz-Metzger methods. The antibacterial and antifungal activities of the ligand, metal salt and metal complexes have been tested. The data show that the complexes exhibit significant action against some of the four bacterial species but no effect on two species of fungi compared with gemifloxacin. The antitumor activity of the ligands and their complexes has been evaluated against breast (MCF-7) and colon (HCT-116) cancer cells.