Heptacoordinate tin(IV) compounds derived from pyridine Schiff bases: synthesis, characterization, in vitro cytotoxicity, anti-inflammatory and antioxidant activity.

Tin(IV) complexes 2a--q derived from pyridine Schiff bases were prepared and characterized. Four complexes of this series were evaluated in vitro against different carcinogenic cell lines; besides their anti-inflammatory and antioxidant properties were also tested. Combination of mass spectrometry, multinuclear NMR and X-ray diffraction techniques evidenced the formation of heptacoordinated monomeric species. The X-ray diffraction analysis of 2a, 2b, 2i, 2j and 2n led to establish the heptacoordination around the tin atom in solid state and also revealed that the ligand occupies the equatorial positions of the distorted pentagonal bipyramidal geometry and the two alkyl or aryl groups the axial positions. The in-vitro study for complexes 2a--d against six tumor cell lines showed varied antiproliferative activity, the IC50 for all tested complexes was lower than that of the cis-platin. Compounds 2a--d also exhibited anti-inflammatory activity where complex 2c resulted to be more active (IC50=0.11 microM) than the indomethacin IC50=0.27 microM which was used as reference. The antioxidant activity in rat brain homogenate on inhibition of thiobarbituric acid reactive substances (TBARS) indicated that 2c (IC50=1.77 microM) is more active than the quercetine (4.11 microM) and alpha-tocopherol (IC50=569.09 microM).