Synthesis, spectroscopic characterization, X-ray crystal structure and biological activities of homo- and heterobimetallic complexes with potassium-1-dithiocarboxylatopiperidine-4-carboxylate

Abstract

Six homobimetallic organotin(IV) carboxylates dithiocarboxylates of the general formula R2(Cl)SnSSCLCOOSn(Cl)R2 (R=Me: 1; n-Bu: 2; Ph: 3)/R3SnSSCLCOOSnR3 (R=Me: 4; n-Bu: 5; Ph: 6), a trinucleartin(IV) derivative [Ph2(Cl)SnSSCLCOO]2SnPh2 (7), three heterobimetallic (Sn, Pd) products of the type Cl2PdSSCLCOOSnR3 (R=Me: 8; Bu: 9; Ph: 10) and a palladium complex KOOCLCSSPdSSCLCOOK (11) were synthesized from potassium 1-dithiocarboxylatopiperidine-4-carboxylate (KSSCLCOOK) insitu. The structures of the complexes were verified by spectroscopic techniques (FT-IR, UV–Visible, 1H NMR, 13C NMR, EI-MS/ESI) and TGA. FT-IR data indicated a bidentate binding mode of the carboxylate/dithiocarbamate group, with tetra and penta-coordinated arrangements around Pd(II) and Sn(IV) centers in solid state. In solution state, a trigonal bipyramidal environment around Sn(IV) and a square planar geometry of Pd(II) was justified by NMR (1H and 13C) and UV–Vis spectroscopies. In heteronuclear products (8–10), the ligand develops linkage through oxygen and sulfur donor sites to Sn(IV) and Pd(II), respectively. The mass fragmentation and thermal degradation patterns were excellently agreed with the molecular composition of products. Single crystal XRD analysis of the complex 6 demonstrated that the geometry of sulfur bonded tin(IV) lies between tetrahedral and trigonal bipyramidal, while a distorted trigonal bipyramidal arrangement was verified for oxygen bonded Sn(IV). The synthesized complexes exhibited antimicrobial activities against various strains of bacteria and fungi by disc diffusion method and their minimal inhibitory concentrations were also found. The nature of the coordinated metal played a major role in biological actions of such complexes. While Pd(II) incorporation chiefly induces SS-DNA binding capacity and ALPs inhibition in complexes, the coordination with Sn(IV) stimulates the antibacterial and antifungal potentials. The complexes exhibited sufficiently lower hemolytic activities as compared to triton X-100 (positive control, 100% lysis) and higher than PBS (negative control, 0% lysis).