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Published October 29, 2007 | Supplemental Material
Journal Article Open

Charge Separation in a Ruthenium-Quencher Conjugate Bound to DNA


A novel tris heteroleptic dipyridophenazine complex of ruthenium(II), [{Ru(phen)(dppz)(bpy'-his)}{Ru(NH_3)_5}]^(5+), containing a covalently tethered ruthenium pentammine quencher coordinated through a bridging histidine has been synthesized and characterized spectroscopically and biochemically in a DNA environment and in organic solvent. Steady-state and time-resolved luminescence measurements indicate that the tethered Ru complex is quenched relative to the parent complexes [Ru(phen)(dppz)(bpy')]^(2+) and [Ru(phen)(dppz)(bpy'-his)]^(2+) in DNA and acetonitrile, consistent with intramolecular photoinduced electron transfer. Intercalated into guanine-containing DNA, [{Ru(phen)(dppz)(bpy'-his)}{Ru(NH_3)_5}]^(5+), upon excitation and intramolecular quenching, is capable of injecting charge into the duplex based upon the EPR detection of guanine radicals. DNA-mediated charge transport is also indicated using a kinetically fast cyclopropylamine-substituted base as an electron hole trap. Guanine damage is not observed, however, in measurements using the guanine radical as the kinetically slower hole trap, indicating that back electron-transfer reactions are competitive with guanine oxidation. Moreover, transient absorption measurements reveal a novel photophysical reaction pathway for [{Ru(phen)(dppz)(bpy'-his)}{Ru(NH_3)_5}]^(5+) in the presence of DNA that is competitive with the intramolecular flash-quench process. These results illustrate the remarkably rich redox chemistry that can occur within a bimolecular ruthenium complex intercalated in duplex DNA.

Additional Information

© 2007 American Chemical Society. Received June 28, 2007. Publication Date (Web): October 2, 2007. We are grateful to the NIH for their financial support. We also thank M.C. DeRosa and E. Yavin for technical assistance.

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Supplemental Material - ic701276t_si_002.pdf


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