Unprecedented palladium(ii) complex containing dipodal 1,3,4-thiadiazole derivatives: synthesis, structure, and biological and thermal investigations

Abstract

A novel mononuclear palladium(II) complex, [Pd(L)Cl₂]·DMF (1·DMF, L = 1,4-bis(5-amino-1,3,4-thiadiazol-2-sulfanyl-methyl)benzene), has been synthesized and characterized by elemental analysis, FT-IR and ¹H NMR spectroscopy and single-crystal X-ray diffraction. On the basis of the molecular structure, in 1·DMF, a ligand acts as a bidentate chelating one using its endocyclic nitrogen atoms. The biological activities of the free ligand and its palladium complex including cytotoxic activity towards the human colon cancer cell line (HCT-116) and antibacterial activity against one Gram-negative strain (Escherichia coli (ATCC 25922)) and one Gram-positive strain (Staphylococcus aureus (ATCC 6538)) have been examined. The IC₅₀ value of 1·DMF against HCT-116 was 500 μM, which is much higher than that reported for cisplatin, and hence, the compound exhibited low anticancer efficacy compared to cisplatin. However, it exhibited excellent antibacterial activities against both Gram-negative as well as Gram-positive bacterial microorganisms. Furthermore, the thermal stability of complex 1·DMF was studied by thermal gravimetric analysis (TGA). The resulting product was characterized as highly pure PdO nanoparticles (mean crystallite size: 39 nm) by using a series of techniques including powder XRD, EDAX, and SEM.