Pyridine and pyrimidine functionalized half-sandwich Ru(II)-N heterocyclic carbene complexes: Synthesis, structures, spectra, electrochemistry and biological studies

•New set of Ru-N-Heterocyclic Carbene (Ru-NHC) complexes 1a and 2a were synthesized from NHC ligands.•X-RD structure reveals the half-sandwich geometry of the compounds.•Absorption spectra show the mixed-mode MLCT type transitions.•The compounds show irreversible oxidation in the cyclic voltammograms.•The compounds have exhibited very promising cytotoxic activity against a series of tumor cell lines with optimistic impressive IC50 values.•This promising observation may lead to new drug molecules in tumor-selective therapeutic strategies. New set of Ru-N-Heterocyclic Carbene (Ru-NHC) complexes 1a and 2a were synthesized from their ligand precursors 1-Methyl-2-pyridin-2-yl-2H-imidazo[1,5-a]pyridin-4-ylium hexafluorophosphate (1) and 1-Methyl-2-pyrimidin-2-yl-2H-imidazo[1,5-a]pyridin-4-ylium hexafluorophosphate (2). The molecules were characterized and their structures were investigated through single crystals X-ray diffraction. The overall coordination around the Ru center can be described as a half-sandwich geometry. Absorption spectra and electrochemical behavior of the complexes were also evaluated, supported by DFT analysis. The complexes were applied on lung (A549), colon (HCT116) and breast (MCF7) cancer cells to examine their in vitro cytotoxicity activity. [Display omitted]