Synthesis, Spectroscopic and Antimicrobial Studies of Homo- and Heteronuclear Tin(IV)/Pd(II) Complexes of 2-Amino-6-(Dithiocarboxyamino)Hexanoic Acid

Homobimetallic organotin(IV) carboxylates dithiocarboxylates, Ph2SnLCS2Sn(Cl)Ph2 (1) and Ph3SnHLCS2SnPh3 (2) were synthesized by a room temperature reaction of l-lysine monohydrate (H2LH) with potassium hydroxide, carbon disulfide and Ph3SnCl/Ph2SnCl2 in methanol. Heterotrinuclear complexes (Bu2SnLCS2)2Pd (3) and (Bu2SnLCS2)2Pd (4) were also synthesized by a reaction of H2LH with KOH, CS2 and PdCl2(aq) in methanol followed by the treatment with n-Bu2SnCl2/Ph2SnCl2. The products were characterized by elemental analysis, FT-IR, multinuclear NMR (1H, 13C and 119Sn) and electron ionization mass spectroscopy (EIMS). The elemental analysis and mass spectrometry verified the molecular composition and structures of complexes. FT-IR spectroscopy demonstrated monodentate binding behavior of the carboxylate group and chelating mode of the dithiocarbamate moiety. The diorganotin(IV) derivatives 1, 3 and 4 convert their solid-state tetra-coordinated structures into trigonal bipyramidal arrangements in solution. However, triphenyltin(IV) derivative 2 exhibited penta-coordinated environment around Sn(IV) in the solid-state and tetrahedral configuration in the solution form. A square planar environment around Pd(II) was exhibited in the solid state. The investigated products displayed antibacterial/antifungal potential, and their minimal inhibitory concentrations (MIC) values were also demonstrated. The nature of the coordinated metals (Sn + Sn or Sn + Pd) and the substitution pattern at tin play a major role in biological actions of these products. The heterometallic (Pd, Sn) products possessed more potential against fungi than bacteria. The heterobimetallic dibutyltin(IV) complex 3 has shown the lowest hemolytic activity (10.76%), while its phenyltin(IV) counterpart 4 possessed the highest cytotoxicity (50.11%).