Synthesis and Characterization of Iridium(III) Cyclometalated Complexes with Oligonucleotides: Insights into Redox Reactions with DNA

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• 作者：Fangwei Shao ; Benjamin Elias ; Wei Lu ; Jacqueline K. Barton
• 刊名：Inorganic Chemistry
• 出版年：2007
• 出版时间：November 26, 2007
• 年：2007
• 卷：46
• 期：24
• 页码：10187 - 10199
• 全文大小：387K
• 年卷期：v.46,no.24(November 26, 2007)
• ISSN：1520-510X

文摘

Heteroleptic cyclometalated complexes of Ir(III) containing the dipyridophenazine ligand are synthesized throughthe direct introduction of a functionalized dipyridophenazine ligand onto a bis(dichloro)-bridged Ir(III) precusor andcharacterized by ¹H NMR, mass spectrometry, as well as spectroscopic and electrochemical properties. The excitedstate of the Ir(III) complexes have sufficient driving force to oxidize purines and to reduce pyrimidine nucleobases.Luminescence and EPR measurements of the Ir(III) complex with an unmodified dppz bound to DNA show theformation of a guanine radical upon irradiation, resulting from an oxidative photoinduced electron-transfer process.Evidence is also obtained indirectly for reductive photoinduced electron transfer from the excited complex to thethymine base in DNA. We have also utilized cyclopropylamine-substituted nucleosides as ultrafast kinetic traps toreport transient charge occupancy in oligonucleotides when DNA is irradiated in the presence of noncovalentlybound complexes. These experiments establish that the derivatized Ir(III) complexes, with photoactivation, cantrigger the oxidation of guanine and the reduction of cytosine.