Synthesis, Characterization, and Photochemistry of Novel Ru(II) Complexes for Light-Induced Enzyme Inhibition and Singlet Oxygen Generation

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The Ohio State University

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Photodynamic therapy (PDT) is a developing cancer treatment involving the use of a photoactive drug molecule that is inactive in the dark and activated by low energy light. A new pathway that is being explored is the caging of cytotoxic molecules by protecting groups that are photolabile. Divalent ruthenium complexes exhibit photoinduced ligand exchange, making these complexes prime candidates for investigation as new PDT agents. The synthesis and characterization by 1H NMR of four ruthenium(II) complexes, [Ru(tpy)(NN)L](PF6)2 where NN = bpy (bpy = 2,2ʹ-bipyridine) or dppn (dppn = benzo[i]-dipyrido[3,2-a:2ʹ,3ʹ-c]phenazine) and L = CH3CN or Cbz-Leu-NHCH2CN, is reported. [Ru(tpy)(NN)Cbz-Leu-NHCH2CN](PF6)2 are proposed as potential PDT agents, as Cbz-Leu-NHCH2CN is a cathepsin K inhibitor capable of reducing or hindering tumor growth and metastasis. The photoinduced ligand exchange of all four complexes in water upon irradiation with visible light was monitored by electronic absorption spectroscopy. Complexes with a dppn ligand required longer irradiation times than complexes with a bpy ligand. The production of singlet oxygen in [Ru(tpy)(dppn)(CH3CN)]2+ was tracked with emission spectroscopy and the use of an emissive singlet oxygen scavenger, DPBF = 1,3-diphenylisobenzofuran, and the quantum yield is reported, ΦΔ = 0.62(6).



ruthenium (II), enzyme inhibition, singlet oxygen, photoinduced ligand exchange, photodynamic therapy