Synthesis, spectroscopy and biological studies of triphenyltin(IV) derivatives with carboxylated Schiff bases

Schiff bases (S1-S8) were prepared by the reaction of 4-aminophenylacetic acid/5-aminoisophthalic acid with benzaldehyde/acetophenone/benzophenone/anthraquinone in ethanol. The sodium salts (NaS1-NaS8) of the Schiff bases were reacted further with triphenyltin(IV) chloride in methanol for 4 h to produce the organotin derivatives (C1-C8). The structures of the synthesized products (S1-S8 and C1-C8) were verified by elemental analysis, FT-IR analysis, H-1 NMR spectroscopy, and thermogravimetry. Elemental analysis (CHN) data agreed well with the chemical composition of compounds. FT-IR spectroscopy demonstrated the isobidentate coordination mode of the carboxylate moiety and a trigonal bipyramidal geometry of Sn(IV) in the solid state of complexes. Proton NMR spectra displayed the signals of the Schiff base skeleton as well as the triphenyltin(IV) moieties in the complexes C1-C8 in their anticipated regions. The thermogravimetric analysis has shown a good agreement between the observed percentages of the evolved contents and residues and the theoretically calculated values. The Schiff bases have shown higher thermal stabilities as compared to their organotin(IV) derivatives, owing to stronger hydrogen bonding in the former case. The complexes exhibited higher antibacterial potential as compared to their free ligand precursors against the tested bacteria (Bacillus subtilis and Escherichia coli). The biological activities were dependent upon the structures of investigated products, nature of incorporated ligand and type (gram-positive or gram-negative) of the bacterial strains. The compounds were also tested for their in vitro hemolytic effects on human red blood cells while using PBS as a negative control (0% lysis) and triton X-100 as a positive control (100% lysis). Cytotoxicity values lie in the range of 1.5-7.9%, which is an acceptable range and renders the safe medicinal uses of all the synthesized products.