Crystal structure and antibacterial activity of polyoxometalate cobalt-ciprofloxacin complex

Abstract

A new antibacterial complex based on the quinolone antibacterial drug ciprofloxacin (CF) and the polyoxometalates (POMs), [Co II (C17H18FN3O3)2]2H2[SiW12O40]·2H2O (1), has been synthesized and comprehensively characterized by elemental analyses, IR, and single crystal X-ray diffraction approaches. Single-crystal structural analysis revealed that complex 1 is composed of Keggin clusters grafted by binuclear cobalt clusters and water molecules. Moreover, we observed that complex 1 formed inorganic-organic hybrid chains via covalent bonds, and could also form a 2D supramolecular layer structure by N··O stacking. In this work, we assessed the antibacterial activities of complex 1 using Escherichia coli, Staphylococcus aureus, and Bacillus subtilis strains. In general, we observed that the antibacterial activities of complex 1 were slightly higher than that of free CF at the same mass concentrations. Overall, the results suggest that introduction of POMs to modify the CF not only affects the final structure of CF but also affects its antibacterial activities.