Tin(IV) Schiff base complexes derived from pyridoxal: Synthesis, spectroscopic properties and cytotoxicity

The synthesis of monomeric pentacoordinated diorganotin(IV) complexes derived from pyridoxal hydrochloride and 4- or 5-R-substituted ortho-aminophenols is described. The complexes were characterized using UV–visible, infrared, mass, 1H NMR, 13C NMR and 119Sn NMR spectral techniques. The molecular structure of three complexes was established using X-ray diffraction: 3b and 3d show a distorted trigonal bipyramidal geometry, in which the basal plane is defined by the butyl groups and the iminic nitrogen atom, whereas the oxygen atoms from the aromatic ring occupy axial positions; in contrast, complex 3e exhibits a square pyramidal geometry. The cytotoxic activity of all complexes against human cell lines U-251 (glioblastoma), K-562 (chronic myelogenous leukemia), HCT-15 (human colorectal cancer), MCF-7 (human breast cancer) and SKLU-1 (non-small-cell lung cancer) was evaluated, and the inhibitory percentage values indicated higher activity than the reference standard, cisplatin. Acute toxicity studies were performed in vivo for the prepared complexes to determine the lethal medium dose (LD50) after intraperitoneal administration to mice.