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  1. Two new tris-heteroleptic Ru( ii ) complexes with triphenylphosphine (PPh 3 ) coordination, cis -[Ru(phen) 2 (PPh 3 )(CH 3 CN)] 2+ (1a, phen = 1,10-phenanthroline) and cis -[Ru(biq)(phen)(PPh 3 )(CH 3 CN)] 2+ (2a, biq = 2,2′-biquinoline), were synthesized and characterized for photochemotherapeutic applications. Upon absorption of visible light, 1a exchanges a CH 3 CN ligand for a solvent water molecule. Surprisingly, the steady-state irradiation of 2a followed by electronic absorption and NMR spectroscopies reveals the photosubstitution of the PPh 3 ligand. Phosphine photoinduced ligand exchange with visible light from a Ru( ii ) polypyridyl complex has not previously been reported, and calculations reveal that it results from a trans -type influence in the excited state. Complexes 1a and 2a are not toxic against the triple negative breast cancer cell line MDA-MB-231 in the dark, but upon irradiation with blue light, the activity of both complexes increases by factors of >4.2 and 5.8, respectively. Experiments with PPh 3 alone show that the phototoxicity observed for 2a does not arise from the released phosphine ligand, indicating the role of the photochemically generated ruthenium aqua complex on the biological activity. These complexes represent a new design motif for the selective release of PPh 3 and CH 3 CN for use in photochemotherapy. 
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  3. ABSTRACT

    We report the synthesis, photochemical and biological characterization of two new Ru(II) photoactivated complexes based on [Ru(tpy)(Me2bpy)(L)]2+(tpy = 2,2':6',2''‐terpyridine, Me2bpy = 6,6'‐dimethyl‐2,2'‐bipyridine), where L = pyridyl‐BODIPY (pyBOD). Two pyBOD ligands were prepared bearing flanking hydrogen or iodine atoms. Ru(II)‐bound BODIPY dyes show a red‐shift of absorption maxima relative to the free dyes and undergo photodissociation of BODIPY ligands with green light irradiation. Addition of iodine into the BODIPY ligand facilitates intersystem crossing, which leads to efficient singlet oxygen production in the free dye, but also enhances quantum yield of release of the BODIPY ligand from Ru(II). This represents the first report of a strategy to enhance photodissociation quantum yields through the heavy‐atom effect in Ru(II) complexes. Furthermore, Ru(II)‐bound BODIPY dyes display fluorescence turn‐on once released, with a lead analog showing nanomolar EC50values against triple negative breast cancer cells, >100‐fold phototherapeutic indexes under green light irradiation, and higher selectivity toward cancer cells as compared to normal cells than the corresponding free BODIPY photosensitizer. Conventional Ru(II) photoactivated complexes require nonbiorthogonal blue light for activation and rarely show submicromolar potency to achieve cell death. Our study represents an avenue for the improved photochemistry and potency of future Ru(II) complexes.

     
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