Synthesis, structural characterization, and evaluation of biological activity of organotin(IV) complexes with 2-hydroxy-5-methoxybenzaldehyde-N(4)-methylthiosemicarbazone

The reaction of organotin(IV) chloride(s) with 2-hydroxy-5-methoxybenzaldehyde-N(4)-methylthiosemicarbazone [H(2)dmmt, (1)] in the presence of potassium hydroxide yielded four new stable complexes, namely, [MeSnCl(dmmt)] (2), [BuSnCl(dmmt)] (3), [PhSnCl(dmmt)] (4), and [Ph2Sn(dmmt)] (5). The new compounds were characterized using CHN analyses, molar conductivity, UV-Vis, FT-IR, and H-1, C-13, and Sn-119 NMR spectral studies. The molecular structures of H(2)dmmt (1) and its complex 5 were determined using X-ray crystallography. The X-ray crystal studies of complex 5 showed the trigonal bipyramidal geometry around the tin(IV) atom. The solid-state structure of complex 5 revealed that the dinegative tridentate ligand (1) is coordinated with the tin(IV) moiety via phenolic-O, azomethine-N, and thiolate-S atoms. The biological activities of the organotin(IV) complexes were investigated against a human colorectal (HCT 116) cell line and exhibited strong cytotoxic activities in the following order: 5 > 4 > 2 > 3 > H(2)dmmt. The organotin(IV) complexes (2-5) showed significant activity when compared with the standard drug, 5-fluorouracil (IC50 = 7.58 mu M), and the parent ligand (IC50 = 7.19 mu M). These results show that organotin(IV) complexes may be designed as new metal-based drugs in the future. (C) 2016 Elsevier B.V. All rights reserved.