In the course of research, a series of complexes with general the formula S4-nSnLn (n=1,2,3) have been synthesized by the reaction of di- and triorganotin chlorides with the sodium salts of various acids in dry toluene. The di-n-butyl and di-n-octyl derivatives were synthesized by treating the corresponding organotin oxides in 1:2 molar ratios, whereas the triphenyl and tricyclohexyl derivatives were prepared by reacting the corresponding hydroxides with the ligand acid in 1:1 molar ratios in dry toluene, using a Dean and Stark apparatus for the concomitant removal of water.
The bonding behavior of donor groups and structural assignments of the synthesized compounds were studied using different analytical techniques such as FT-IR, multinuclear (1H, 13C, 119Sn) NMR, mass spectrometry and X-ray single crystal analysis. It is concluded that diorganotin dicarboxylates are hexa-coordinated as solids, based on skew-trapezoidal geometry and there exists an equilibrium between hexa- and penta-coordinated states in non-coordinating solvents. Triorganotin(IV) carboxylates behave as penta-coordinate linear polymers in the solid state with a trans-R3SnO2 geometry for tin, and tetra-coordinated monomers in solution.
Biological activity tests of the synthesized di- and triorganotin(IV) carboxylates were made against various medically important bacteria and fungi by agar well diffusion and agar tube dilution methods, respectively. Most of the compounds were found to be biologically active having a varying degree of activity against different bacteria. Their activity is lower than the reference drugs.
The microbial toxicity studies demonstrated that triorganotin(IV) carboxylates are more fungicidal than diorganotin(IV) derivatives under identical conditions. This is due to the fact that an increase of R groups on the tin(IV) atom enhances the biological activity of organotin(IV) carboxylates.
These compounds were also evaluated for their cytotoxicity, using the Brine-shrimp lethality bioassay method. With the exception of a few species, all compounds were found to be toxic.
The antitumor activity of the synthesized compounds were also determined by using the ‚€œantitumor potato disc assay method‚€Ě. Some of the compounds were found to have excellent antitumor activities, causing complete inhibition of tumor cells. Whereas other compounds have mild antitumour activities.