Synthesis, characterization and biocidal activities of heterobimetallic complexes having tin(IV) as a padlock

A mononuclear precursor complex, [(CH3)2Sn(tpdtc)] and several of its heterobimetallic derivatives of the type, [(CH3)2Sn(tpdtc)]MCl2 have been synthesized by the simple addition reaction of transition metal chlorides, MCl2·nH2O where tpdtc = tetraethylenepentamine bis(dithiocarbamate) anion, M = Fe(II), Co(II), Ni(II), Cu(II) and Zn(II). The synthesized complexes have been systematically characterized by the physicochemical and spectroscopic techniques. A square-pyramidal geometry has been proposed for all the transition metal atoms with chloride ions occupying the axial while the three nitrogen atoms occupying the equatorial positions. A symmetrical bidentate coordination has been observed for the dithiocarbamato moiety leading to the formation of 18 member cavity. The thermal studies reveal that the mononuclear complex decomposes in three stages while its heterobimetallic analog exhibits a simple two-stage profile. The conductivity measurement data (1 mmol solution) implies a non-electrolytic behavior for all the complexes as evident by their low conductivity values obtained at room temperature. The heterobimetallic complexes have also been tested against the bacterial (Escherichia coli and Pseudomonas aeruginosa) and antifungal strains (Aspergillus niger and Fusarium oxysporum). All the complexes were found to be active against the test organisms and maximum activity was found for [(CH3)2Sn(tpdtc)]CuCl2 complex.