Relationships between the carbon-oxygen stretching frequencies of carboxylato complexes and the type of carboxylate coordination

Eight di-o-chlorobenzyltin complexes (1a ∼ 4b), namely {[X-C6H4(O)CN-NC(R’)COO](o-Cl-C6H4CH2)2Sn(CH3OH)}2 (X = H (1), 2-OH (2), 4-CH3 (3), 4-t-Bu- (4); R’= Ph (a) or Bn (b)), were prepared from the reaction of hydrazide, benzoylformic acid (or sodium phenylpyruvate) and di-o-chlorobenzyltin dichloride with heating reflux. All complexes were characterized by FT-IR spectroscopy, 1H, 13C, and 119Sn NMR spectroscopy, HRMS, and TGA. The single-crystal structure of complexes 1a, 2a, 3a, and 4a have been obtained. The crystal structure shows that the complexes are also centrosymmetric dimer distannoxane and there was a Sn2O2 four-membered ring in the middle of the molecule. The anticancer activity of all complexes was tested against the cancer cell lines NCI-H460, MCF-7, and HepG2. Complex 3a is more potent as a potential anticancer agent than other complexes and cisplatin. The DNA binding activities of the 3a were studied by UV–visible absorption spectrometry, fluorescence competitive, viscometry, and molecular docking, results shown 3a can be well embedded in the groove of DNA.