Synthesis, characterization, photophysical and electrochemical properties, and biomolecular interaction of 2,2′-biquinoline based phototoxic Ru(ii)/Ir(ii) complexes

Abstract

The phototoxic nature of drugs has been seen to convey immense importance in photo activated chemotherapy (PACT) for the selective treatment of disease. Rationally, in order to eradicate the vehemence of cancer in a living body, the design of phototoxic molecules has been of growing interest in research to establish a selective strategy for cancer therapy. Therefore, the present work portrays the synthesis of a phototoxic anticancer agent by incorporating ruthenium(II) and iridium(III) metals into a biologically active 2,2′-biquinoline moiety, BQ. The complexes, RuBQ and IrBQ, have been revealed as effective anticancer agents with remarkable toxicity in the presence of light compared to the dark towards HeLa and MCF-7 cancer cell lines due to the production of a profuse amount of singlet oxygen (¹O₂) upon irradiation by visible light (400–700 nm). Complex IrBQ exhibited the best toxicity (IC₅₀ = 8.75 μM in MCF-7 and 7.23 μM in HeLa) in comparison to the RuBQ complex under visible light. RuBQ and IrBQ displayed considerable quantum yields (Φ_f) along with a good lipophilic property, indicating the cellular imaging capability of both complexes upon significant accumulation in cancer cells. Also, the complexes have shown significant binding propensity with biomolecules, viz. deoxyribonucleic acid (DNA) as well as serum albumin (BSA, HSA).