A method is described here by which to dope ruthenium(II) bis(2,2'-bipyridine) (2,2'-bipyridyl-5,5'-dicarboxylic acid), RuDCBPY, into a UiO-67 metal-organic framework (MOF) derivative in which 2,2'-bipyridyl-5,5'-dicarboxylic acid, UiO-67-DCBPY, is used in place of 4,4'-biphenyldicarboxylic acid. Emission lifetime measurements of the RuDCBPY triplet metal-to-ligand charge transfer, (3)MLCT, excited state as a function of RuDCBPY doping concentration in UiO-67-DCBPY are discussed in light of previous results for RuDCBPY-UiO-67 doped powders in which quenching of the (3)MLCT was said to be due to dipole-dipole homogeneous resonance energy transfer, RET. The bulk distribution of RuDCBPY centers within MOF crystallites are also estimated with the use of confocal fluorescence microscopy. In the present case, it is assumed that the rate of RET between RuDCBPY centers has an r(-6) separation distance dependence characteristic of Förster RET. The results suggest (1) the dimensionality in which RET occurs is dependent on the RuDCBPY concentration ranging from one-dimensional at very low concentrations up to three-dimensional at high concentration, (2) the occupancy of RuDCBPY within UiO-67-DCBPY is not uniform throughout the crystallites such that RuDCBPY densely populates the outer layers of the MOF at low concentrations, and (3) the average separation distance between RuDCBPY centers is ∼21 Å.
Appending anthracene units to [(bpy)2Ru(dpp)]2+ results in Ru(II) agents that exhibit dynamic photoreactivity towards DNA and protein. [(Anthbpy)(bpy)Ru(dpp)]2+ and [(Anthbpy)2Ru(dpp)]2+ are the first metal-organic Ru(II) agent with dpp ligands shown to photomodify DNA in the presence or absence of oxygen, while also binding protein in an oxygen-dependent manner.
The synthesis of Ru(II) derivatives [(AnthbpyMe)(bpy)Ru(dpp)] 2+ (2) and [(AnthbpyMe) 2 Ru(dpp)] 2+ (3), and the analysis of their excited state properties as well as their photocytotoxicity against glioma cells are reported. Complexes 2 and 3 absorb visible light with metal-to-ligand charge transfer (MLCT) transitions at λ max = 459 nm (16,000 M-1 cm-1) and λ max = 461 nm (21,000 M-1 cm-1), respectively. The complexes exhibit bichromatic properties with the 3 MLCT emission centered at λ em = 661 nm and λ em = 663 nm for 2 and 3, respectively, while the anthracene motif(s) has emission from 450-560 nm. The anthracene unit(s) quench the 3 MLCT to give quantum yields (lifetime, τ) of Φ em = 0.0059 (τ = 398 ns) and Φ em = 0.0011 (τ = 414 ns) for 2 and 3, respectively. The quenching rates were found to be 6.61 × 10 5 s-1 for 2 and 5.64 × 10 5 s-1 for 3. Electrochemistry reveals an irreversible anthracene oxidation at 1.23-1.28 V, while the Ru III/II oxidation process occurs at a potential of 1.53-1.55 V. The complexes displayed a quasi-reversible reduction couple attributed to dpp 0/-1 at 0.98 V. Cytotoxicity of both complexes towards F98 glioma cells was moderate in the absence of light and substantially enhanced with visible light.
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