Long-Range Electron and Hole Transport through DNA with Tethered Cyclometalated Iridium(III) Complexes

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• 作者：Fangwei Shao ; Jacqueline K. Barton
• 刊名：Journal of the American Chemical Society
• 出版年：2007
• 出版时间：November 28, 2007
• 年：2007
• 卷：129
• 期：47
• 页码：14733 - 14738
• 全文大小：112K
• 年卷期：v.129,no.47(November 28, 2007)
• ISSN：1520-5126

文摘

A cyclometalated complex of Ir(III) is covalently tethered to DNA oligonucleotides and serves asboth a photooxidant and photoreductant in the study of DNA-mediated hole transport (HT) and electrontransport (ET). Spectroscopic and melting temperature studies support intercalation of the tethered complexinto the DNA duplex through the functionalized dppz ligand. Using these tethered assemblies, ET and HTis initiated in DNA by the same photoredox probe. Cyclopropylamine substituted bases, N₄-cyclopropylcytosine (^CPC) and N₂-cyclopropylguanine (^CPG) are used as kinetically fast electron and hole traps to probethe resulting electron migration processes after direct irradiation of the tethered Ir assembly. Oxidation of^CPG and ^CPC is promoted efficiently by HT from photoexcited Ir(III) when the modified bases are positionedin the purine strands of the A-tract. In contrast, when ^CPC is embedded in a pyrimidine tract, ET to yieldreductive decomposition is observed. Thus, the Ir(III)-tethered DNA assembly containing cyclopropyl-modifiedbases provides a unique model system to explore the two DNA-mediated electron migration processesusing the same photoredox probe and the same DNA bridge.