New organotin(IV) complexes with N(4)-methylthiosemicarbazone derivatives prepared from 2,3-dihydroxybenzaldehyde and 2-hydroxy-5-methylbenzaldehyde: synthesis, characterization, and cytotoxic activity

Abstract

The N(4)-methylthiosemicarbazone derivatives H₂DDMT (1) and H₂DMMT (2) have been prepared from the reaction of 4-methylthiosemicarbazide with 2,3-dihydroxybenzaldehyde and 2-hydroxy-5-methylbenzaldehyde, respectively. Six new organotin(IV) complexes, [MeSnCl(DDMT)] (3), [BuSnCl(DDMT)] (4), [PhSnCl(DDMT)] (5), [MeSnCl(DMMT)] (6), [BuSnCl(DMMT)] (7), and [PhSnCl(DMMT)] (8) have been synthesized by direct reaction of corresponding organotin(IV) chloride(s) with these ligands. The ligands and their compounds have been characterized by elemental analysis, molar conductivity, UV–Vis, FT-IR, and NMR (¹H, ¹³C, and ¹¹⁹Sn) spectroscopy. The molecular structures of 1 and 2 were determined by X-ray crystallography. Spectroscopic data suggested that the ligands were coordinated to tin(IV) as dinegative tridentate via phenoxide-O, azomethine-N, and thiolate-S atoms. The crystal structures revealed that the ligands exist in thione form in the solid state. In vitro cytotoxicity assays were carried out for all the compounds against MCF-7 cancer cell line. The results have shown that different organotin(IV) groups showed characteristic differences in their biological activity.

Graphical abstract

Six new organotin(IV) complexes with 2,3-dihydroxybenzaldehyde-N(4)-methylthiosemicarbazone H₂DDMT (1) and 2-hydroxy-5-methylbenzaldehyde-N(4)-methylthiosemicarbazone H₂DMMT (2), [MeSnCl(DDMT)] (3), [BuSnCl(DDMT)] (4), [PhSnCl(DDMT)] (5), [[MeSnCl(DMMT)] (6), [BuSnCl(DMMT)] (7), and [PhSnCl(DMMT)] (8) have been synthesized. The ligands are coordinated to tin(IV) through the phenoxide-O, azomethine-N, and thiolate-S as a dinegative tridentate chelating agent; the coordination number of tin is five. In vitro cytotoxicity assays against MCF-7 cancer cell line showed that 3–8 possess activity.

Keywords:

• N(4)-methylthiosemicarbazones
• Organotin(IV) complexes
• Synthesis
• Characterization
• Crystal structure
• Cytotoxicity

Acknowledgements

The authors would like to thank The World Academy of Sciences (TWAS) and Universiti Sains Malaysia (USM). We also thank the Bangladesh Petroleum Exploration and Production Co. Ltd. (BAPEX), Bangladesh for the study leave to M.A. Salam.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the School of Chemical Sciences, Universiti Sains Malaysia (USM) under the Research University (RU) [grant number 1001/PKIMIA/811217].