Synthesis, crystal structures and biological activity of palladium(II) complexes with 1-methyl-1H-1,2,3,4-tetrazole-5-thiol and substituted 2,2′-bipyridines

Abstract

Reaction of PdCl₂ with 1-methyl-1H-1,2,3,4-tetrazole-5-thiol (Hmtzt) in the presence of 5,5′-dimethyl-2,2′-bipyridine (5,5′-dmbipy) and 4,4′-dimethyl-2,2′-bipyridine ligands (4,4′-dmbipy) afforded two new Pd(II) complexes, [Pd(5,5′-dmbipy)(mtzt)₂] (1) and [Pd(4,4′-dmbipy)(mtzt)₂] (2), respectively. The two complexes were thoroughly characterized by elemental analysis, UV-vis, ¹H NMR, IR, luminescence spectroscopy as well as single-crystal X-ray diffraction. Single-crystal X-ray diffraction revealed that central Pd(II) ions in 1 and 2 are tetra-coordinated, presenting distorted and slightly distorted square planar geometry around Pd atom for 1 and 2, respectively. The luminescence properties of free ligands and complexes 1 and 2, in solution, were investigated. The biological evaluation of the Pd(II) complexes showed that they exhibited anticancer activities in a dose-dependent manner against human breast cancer cell lines. Also, their in vitro interaction with DNA were analyzed through spectrophotometric, spectrofluorometric, and gel-electrophoresis which shows the intercalation mode of binding. In conclusion, these palladium complexes represent novel anticancer drug molecules for further study.

Graphical Abstract

Keywords:

• Palladium(II)
• 1-methyl-1H-1,2,3,4-tetrazole-5-thiol
• dimethyl-2,2′-bipyridine
• breast cancer
• DNA interaction

Acknowledgements

Financial support by Damghan, Farhangian, and Tarbiat Modares Universities are gratefully acknowledged.

Disclosure statement

No potential conflict of interest was reported by the author(s).