Synthesis, structures, electrochemical characterizations, theoretical and anticancer studies of Pd(II)-, Pt(II)- NHC complexes

Abstract

We present the synthesis of two novel cationic Pd(II)- and Pt(II)- complexes ligated to a new C ∩ N donor N-heterocyclic carbene (NHC) ligand 3-methyl-1-(1-methyl-2-methylbenzoyl)imidazolin-2-ylidene, (1). Capitalizing 3-methyl-1-(1-methyl-2-methylbenzoyl)imidazolium hexafluorophosphate (1.HPF6), two novel isoelectronic and isostructural [Pd(1)2][PF6]2 (2), and [Pt(1)2][PF6]2 (3) complexes were synthesized. All the compounds were characterized by elemental analysis, 1H NMR, 13C NMR, IR, UV–Vis, mass spectroscopic studies, and finally single-crystal X-ray studies. X-ray crystallographic studies revealed both complexes 2 and 3 adopted square planar geometry. Electrochemical studies revealed Pt(II)/Pt(IV) reversible redox potential at 0.52 V. The catalytic activity of Pd(II)–NHC complex, 2 was tested for Suzuki coupling reactions. The structural assignments were further supported by DFT calculations. Molecular docking studies show a better binding affinity of 3 with Human-DNA Topoisomerase and BCL-2 protein compared to 2 and the scope of the complex 2 and 3 may be used as a drug. Cytotoxicity studies revealed that Pt(II)–NHC complex 3 is more potent than Pd(II)–NHC complex 2 against the breast cancer cell line (MCF-7) (IC50,7.9 ± 0.84 vs 6.0 ± 0.72 μM).