Synthesis, characterization and cytotoxic activity of diorganotin complexes with Schiff base derived from salicylaldehyde and l-tyrosine

Seven diorganotin complexes with the Schiff bases derived from salicylaldehyde and l-tyrosine, R₂Sn[2-O-5-XC₆H₃CH = NCH(CH₂C₆ H₄OH-4)COO] (X = H (1), Br (2); R = Me (a), Et (b), Bu (c), Cy (cyclohexyl) (d)), were synthesized and characterized by elemental analysis, IR, ¹H and ¹³C NMR spectra, and the single-crystal X-ray diffraction. In methanol, the racemization of chiral center of l-tyrosinate fragment occurred and the racemic products were obtained. X-ray analyses of 1c, 1d, and 2a–2c showed that the tin atoms of the complexes exhibit distorted trigonal-bipyramidal geometries. In 1c, 1d, and 2c, the intermolecular O–H⋅⋅⋅O hydrogen bonds connected the molecules into 1-D supramolecular chain or a R ₂ ²(20) macrocyclic dimer, and 2a and 2b formed the 2-D supramolecular network by the intermolecular Sn⋅⋅⋅O and O–H⋅⋅⋅O interactions. Bioassay results indicated that 1a, 1c, and 1d had moderate antibacterial activity against Escherichia coli and 1c, 1d, and 2c belonged to the efficient cytostatic agents against two human tumor cell lines (A549 and HeLa) and the activity tends to follow the order Cy > Bu > Et > Me for the R group attached to tin.