A novel class of Ru(II)-based polypyridyl complexes with an auxiliary salicylaldehyde ligand [Ru(phen)(X-Sal)]BF {X: H (), 5-Cl (), 5-Br (), 3,5-Cl (), 3,5-Br (), 3-Br,5-Cl (), 3,5-I (), 5-NO (), 5-Me (), 4-Me (), 4-OMe (), and 4-DEA (), has been synthesized and characterized by elemental analysis, FT-IR, and H/C NMR spectroscopy. The molecular structure of , , , , and was determined by single-crystal X-ray diffraction analysis which revealed structural similarities. DFT and TD-DFT calculations showed that they also possess similar electronic structures. Absorption/emission spectra were recorded for , , , and . All Ru-complexes, unlike the pure ligands and the complex lacking the salicylaldehyde component, displayed outstanding antiproliferative activity in the screening test (10 μM) against CCRF-CEM leukemia cells underlining the crucial role of the presence of the auxiliary ligand for the biological activity. The two most active derivatives, namely and , were selected for continuous assays showing IC values in the submicromolar and micromolar range against drug-sensitive CCRF-CEM and multidrug-resistant CEM/ADR5000 leukemia cells, respectively. These two compounds were investigated in silico for their potential binding to duplex DNA well-matched and mismatched base pairs, since they showed remarkable selectivity indexes (2.2 and 19.5 respectively) on PBMC cells.
