Molecular basis of the interaction of novel tributyltin(IV) 2/4-[(E)-2-(aryl)-1-diazenyl]benzoates endowed with an improved cytotoxic profile: Synthesis, structure, biological efficacy and QSAR studies

A series of tributyltin(IV) complexes based on 2/4-[(E)-2-(aryl)-1-diazenyl]benzoate ligands was synthesized, wherein the position of the carboxylate and aryl substituents (methyl, tert-butyl and hydroxyl) varies. The complexes, Bu3SnL1–4H (1–4), have been structurally characterized by elemental analysis and IR, NMR (1H, 13C, and 119Sn) and 119Sn Mössbauer spectroscopy. All have a tetrahedral geometry in solution and a trigonal bipyramidal geometry in the solid-state, except for Bu3SnL4H (4) that was ascertained to have tetrahedral coordination by X-ray crystallography. Cytotoxicity studies were carried out on human tumor cell lines A498 (renal cancer), EVSA-T (mammary cancer), H226 (non-small-cell lung cancer), IGROV (ovarian cancer), M19 MEL (melanoma), MCF-7 (mammary cancer) and WIDR (colon cancer). Compared to cisplatin, test compounds 1–4 had remarkably good activity, despite the presence of substantial steric bulk due to Sn–Bu ligands. The quantitative structure–activity relationship (QSAR) studies for the cytotoxicity of organotin(IV) benzoates, along with some reference drug molecules, is also discussed against a panel of human tumor cell lines. Molecular structures of the tributyltin(IV) complexes (1–4) were fully optimized using the PM6 semi-empirical method and docking studies performed with key enzymes associated with the propagation of cancer, namely ribonucleotide reductase, thymidylate synthase, thymidylate phosphorylase and topoisomerase II. The theoretical results are discussed in relation to the mechanistic role of the cytotoxic active test compounds (1–4).

Graphical abstractA series of tributyltin(IV) complexes (1–4) based on 2/4-[(E)-2-(aryl)-1-diazenyl]benzoate ligands (LH) have been synthesized and structurally characterized by elemental analysis and IR, NMR (1H, 13C, and 119Sn) and 119Sn Mössbauer spectroscopy. All the complexes have a tetrahedral geometry in solution and a trigonal bipyramidal geometry in the solid-state, except for Bu3SnL4H (4) that was ascertained to have tetrahedral coordination by X-ray crystallography. Cytotoxicity studies were carried out on human tumor cell lines A498 (renal cancer), EVSA-T (mammary cancer), H226 (non-small-cell lung cancer), IGROV (ovarian cancer), M19 MEL (melanoma), MCF-7 (mammary cancer) and WIDR (colon cancer). The quantitative structure–activity relationship (QSAR) studies for the cytotoxicity of organotin(IV) benzoates, along with some reference drug molecules, is also discussed against a panel of human tumor cell lines. Molecular structures of the tributyltin(IV) complexes (1–4) were fully optimized using the PM6 quantum mechanical method and docking studies performed with key enzymes associated with the propagation of cancer. The theoretical results are discussed in relation to the mechanistic role of the cytotoxic active test compounds (1–4).Figure optionsDownload full-size imageDownload as PowerPoint slide