New Ternary Complexes of Pt(II) with 5-bromo-2-hydroxybenaldehyde N(4)-phenylthiosemicarbazone: Synthesis, Spectroscopic Investigation and Antibacterial Activity

Thiosemicarbazonesas a class of S-donor Schiff bases are an interesting group of bioligands. On the other hand ternary (heteroleptic) complexes formed between metal ions and two different types of bioligandsmay be considered as models for metal ion mediated biochemical interactions.The effect of one ligand on another through the central metal ion in heteroleptic complexes is very important in coordination and biological chemistry. Complexes of Pt(II) are widely used as chemotherapeutic agents and Pt-S interaction may play a significant role in anti-tumour activity of platinum drugs[1-3].In this work, we report the synthesis, spectroscopic characterization and antibacterial activity of ternary Pt(II) complexes with 5-bromo-2-hydroxybenaldehyde N(4)-phenylthiosemicarbazone (H2L). The ligand was prepared by the condensation reaction of the N(4)-phenythiosemicarbazide and corresponding aldehyde. Then the Pt(II) complexes, [PtL(PPh3)].C2H5OH and [PtL(Imd)], have been synthesized by reaction of H2L with K2PtCl4 in presence of PPh3 or imidazole as auxiliary ligands. New complexes were investigated by elemental analysis, IR and 1HNMR spectroscopy. In all complexes thiosemicarbazoneacts as a tridentate dianionic ligand and coordinates via the thiol group, imine nitrogen, and phenolic oxygen. Coordination sphere of complexes are completed by heterocyclic base. The invitro antibacterial activity of ligand and complexes has been evaluated against Gram-positive (Bacillus cereus and Staphylococcus aureus) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria. The results reveal that complexes show good antibacterial activities compared with standard drugs and better activity in comparison to the thiosemoicarbazone (H2L). The complex containing imidazole, [PtL(Imd)], was more active than the complex with PPh3.