Conjugative effects on 1,10-phenanthroline donors boost dual-mode anticancer activity of Ru(II) polypyridyl complexes

• The complexes are designed as “luminophore + linker + drug” together. • The MCD spectrum was first used to compare the MLCT states of the complexes. • Conjugated effect could boost the synergistic therapy effect. Polypyridyl Ru(II) complexes have garnered attention as potential chemotherapeutic and photosensitizers (PS) because of their outstanding optical properties. However, most of Ru-PS are modulated by acceptors since there are lack of strategies to optimize donors, limiting the development of high efficiency Ru-PS. Here, we rationally designed a series of polypyridyl Ru(II) complexes 1 – 4 with improving PDT ability by tuning the conjugated effect of donor, which give a hint to manipulate the electron donating ability of ligands ([Ru(tpy)(MeO-phen)Cl](PF 6 ) ( 1 ), [Ru(tpy)(Amn-phen)Cl](PF 6 ) ( 2 ), [Ru(tpy)(Pip-phen)Cl](PF 6 ) ( 3 ), [Ru(tpy)(Pyr-phen)Cl](PF 6 ) ( 4 )). Also, these Ru complexes contain a concise skeleton, which could be functionalized as luminophore, linker, and drug together due to the distribution change of HOMO and LUMO according to DFT calculations. Moreover, TD-DFT calculations, MCD properties, photocatalytic oxidation of NADH, singlet oxygen quantum yield tests, cellular imaging studies, and MTT assays were also performed to evaluate our conception. Our findings showed that complex 4 is expected to have the multifunctional effect of "traditional chemotherapy + photodynamic therapy" with multiple targets against the nucleus and the mitochondria, with the IC 50 values of 19.59 ± 3.35 μM (dark) and 7.51 ± 0.75 μM (light) respectively.