Synthesis, structural characterization and biological activities of organotin(IV) complexes with 5-allyl-2-hydroxy-3- methoxybenzaldehyde-4-thiosemicarbazone

The organotin(IV) complexes [MeSnCl(L)] ( 2 ), [BuSnCl(L)] ( 3 ), [PhSnCl(L)] ( 4 ) and [Me 2 Sn(L)] ( 5 ) were synthesized by reacting organotin(IV) chloride(s) with 5-allyl-2-hydroxy-3-methoxybenzaldehyde-4-thiosemicarbazone [H 2 L], ( 1 )] in presence of KOH in 1:2:1 molar ratio (metal salt: base:ligand). All the complexes have been characterized by elemental analyses, UV-Vis, FT-IR, 1 H, 13 C and 119 Sn NMR spectral studies. The molecular structure of complex 5 has been confirmed by single crystal X-ray diffraction analysis. The ligand, H 2 L coordinates to Sn(IV) in thiolate form through phenoxide-O, azomethine-N and thiolate-S atoms. The C-Sn-C angle measured from coupling constant 1 J ( 119 Sn, 13 C) for dimethyltin(IV) complex 5 is 123.4 ∘ . The 2 J ( 119 Sn, 1 H) coupling constant values for complex 2 and 5 are 72.4 and 76.3 Hz, respectively. Proposed geometry for five coordinated Sn(IV) atom is a strongly distorted trigonal bipyramid. Biological studies were preformed in vitro against four bacterial strains which have shown better activities and potential as antibacterial agents. Graphical Abstract Organotin(IV) complexes of 5-allyl-2-hydroxy-3-methoxybenzaldehyde-4-thiosemicarbazone were synthesized and characterized by various physico-chemical methods. Crystal structure of dimethyltin(IV) complex was obtained. Ligand (H 2 L) acts as dinegative ONS tridentate chelating agent, coordinated to tin(IV) atom via phenolic oxygen, azomethine nitrogen and thiolate sulphur atoms. In vitro antibacterial studies revealed that the complexes possess significant activity.