Organotin(IV) complexes with 2-hydroxynaphthaldehyde-N(4)-ethylthiosemicarbazone: Synthesis, characterization, and in vitro antibacterial activity

Four new organotin(IV) complexes with 2-hydroxynaphthaldehyde-N(4)-ethylthiosemicarbazone [(H2DNET), (1)] of the type [MeSnCl(DNET] (2), [BuSnCl(DNET)] (3), [PhSnCl(DNET)] (4), and [Ph2Sn(DNET] (5) have been synthesized by the direct reaction of H2DNET (1) with organotin(IV) chloride(s) in the presence of potassium hydroxide in absolute methanol. All the compounds were characterized by elemental analyses, molar conductivity, UV-Vis, IR, H-1, C-13, and Sn-119 NMR spectral studies. The molecular structure of ligand (1) has been confirmed by X-ray single crystal diffraction. Spectroscopic data clearly suggested that Sn(IV) center is coordinated with the ONS tridentate ligand (H2DNET) and exhibits a five-coordinate geometry in solution. Antibacterial studies were carried out in vitro against four bacterial strains. All organotin(IV) compounds (2-5) showed good activity against various bacteria but lower activity than the reference drug (Ciprofloxacin). The results demonstrate that organic groups attached to tin(IV) moiety have significant effect on their biological activities. Among them, diphenyltin(IV) derivative 5 exhibits significantly good activity than the other organotin(IV) derivatives (2-4).