Synthesis, structures, and cytotoxicity insights of organotin(IV) complexes with thiazole-appended pincer ligand.

Diorganotin complexes of the compositions [MeSn(L)] (1), [n-BuSn(L)] (2), [PhSn(L)]⋅CH (3), [BzSn(L)]⋅CH (4) and [n-OctSn(L)] (5) were synthesized by reacting RSnO (R = Me, n-Bu, Ph, Bz or n-Oct) with the N,N-di(thiazol-2-yl)pyridine-2,6-dicarboxamide (HL, where H denotes the two acidic protons) in refluxing toluene. Additionally, the mono-n-butyltin complex [n-BuSn(HL)Cl]·HO (6) was synthesized from n-BuSnCl and HL in acetonitrile. Compounds were characterized by FT-IR, H, C and Sn NMR spectroscopy, while their solid-state structures were examined using single-crystal X-ray diffraction studies. In diorganotin compounds 1-5, the dianionic tridentate ligands (N, N, N) act as κ-N chelators. In 6, the L moiety (O, N, N) acts as a κ-ON tridentate chelator, with involvement of one of the carboxamide oxygen atoms. The coordination polyhedron around the Sn(IV) ion is completed either by two axial Sn-R ligands in compounds 1-5 or by n-Bu and Cl ligands in compound 6, giving rise to distorted trigonal bipyramid or octahedral structures, respectively. The tin NMR results show that the penta-coordinated structures of compounds 1-5 and the hexacoordinated structure of compound 6, observed in the solid-state, are retained in solution. The in vitro antitumor activities of 1-5 were tested on T-47D breast cancer cells. Of these, diphenyltin compound 3 showed the highest anti-proliferative effect, with an IC of 10 ± 1.60 μM. Compound 3 exhibited selective toxicity, potentially inducing apoptosis via reactive oxygen species generation and nuclear changes, indicating promise as a breast cancer treatment. This study is the first to explore thiazole-appended organotin compounds for cytotoxicity.