Synthesis, Structural Elucidation and Biological Activities of Homo and Hetero Bimetallic Complexes Containing Pd(II) and Sn(IV) with Various [O,O] [O,S] and [S,S] Donor Ligands

Abstract

In the present study, monometallic, homo- and heterobimetallic complexes containing tin(IV), tin(IV)-tin(IV) and tin(IV)-palladium(II), respectively with various [O,O], [O,S] and [S,S] donor ligands have been synthesized. The ligands used were 3-[4-(2hydroxyethyl)phenylamido] propenoic acid (HL1), 3-[IH-indazolyl-6-amido]propenoic acid (HL2), 3-[5-methyl-1H-pyrazol-3-amido]propenoic acid (HL3), 3-[4-(2-hydroxyethyl) phenylamido]propanoic acid (HL4), 3-[5-methyl-1H-pyrazol-3-amido]propanoic acid (HL5), 2-[IH-indazolyl-6-amido]benzoic acid (HL6), 3-amino-1,2,4-triazole,5-carboxylic acid (HL7), 1H-1,2,4-triazole-3-thiol (HL8), 2-mercapto-5-methyl benzimidazole (HL9), 5-amino3H-1,3,4-thiadiazole-2-thiol (HL10). The free ligands or their salts were treated with organotin chlorides and/or palladium chloride in methanol/water to synthesize the complexes 1-84. The purity of the products was tested using TLC. The coordination mode of ligands, structural confirmation and geometry assignment of the complexes both in solid and solution states were made, using different analytical techniques such as elemental analysis, IR, UV visible spectroscopy, NMR (1H, 13C), mass spectrometry and X-ray single crystal analysis. IR data suggested a bidentate bonding of the carboxylate (COO−) and dithiocarbamate moieties (CSS−) with few exceptions of monodentate bonding. The triorganotin(IV) complexes exhibited polymeric trigonal bipyramidal geometry in solid state while monomeric tetrahedral geometry in solution state. The chlorodiorganotin(IV) carboxylates/thiocarbamates showed trigonal bipyramidal environment around tin(IV) both in solid and solution state. Spectroscopic data supported the tetrahedral geometry both in chlorodi- and triorganotin(IV) complexes with thiol donor site (-SH) of the ligands. UVvisible absorption data demonstrated a square planar geometry around Pd(II). The mass (EIMS) fragmentation pattern agreed well with the molecular skeleton of the investigated complexes. The synthesized complexes were also screened for their biological activities such as antibacterial, antifungal and cytotoxicity. The results showed that triorganotin(IV) complexes exhibited more bactericidal, fungicidal and cytotoxic effects than diorganotin(IV) complexes. The synthesized complexes possessed hemolytic activities sufficiently lower as compared to triton X-100 and higher than PBS.