Metal-Ligand Charge-Transfer-Promoted Photoelectronic Bergman Cyclization of Copper Metalloenediynes: Photochemical DNA Cleavage via C-4' H-Atom Abstraction
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- 作者：Pedro J. Benites ; Rebecca C. Holmberg ; Diwan S. Rawat ; Brian J. Kraft ; Lee J. Klein ; Dennis G. Peters ; H. Holden Thorp ; and Jeffrey M. Zaleski
- 刊名：Journal of the American Chemical Society
- 出版年：2003
- 出版时间：May 28, 2003
- 年：2003
- 卷：125
- 期：21
- 页码：6434 - 6446
- 全文大小：222K
- 年卷期：v.125,no.21(May 28, 2003)
- ISSN：1520-5126
文摘
Metal-to-ligand charge-transfer (MLCT) photolyses (
395 nm) of copper complexes of cis-1,8-bis(pyridin-3-oxy)oct-4-ene-2,6-diyne (bpod, 1), [Cu(bpod)2]PF6 (2), and [Cu(bpod)2](NO3)2 (3) yieldBergman cyclization of the bound ligands. In contrast, the uncomplexed ligand 1 and Zn(bpod)2(CH3COO)2compound (4) are photochemically inert under the same conditions. In the case of 4, sensitizedphotochemical generation of the lowest energy 3
-* state, which is localized on the enediyne unit, leadsto production of the trans-bpod ligand bound to the Zn(II) cation by photoisomerization. Electrochemicalstudies show that 1, both the uncomplexed and complexed, exhibits two irreversible waves between Epvalues of -1.75 and -1.93 V (vs SCE), corresponding to reductions of the alkyne units. Irreversible, ligand-based one-electron oxidation waves are also observed at +1.94 and +2.15 V (vs SCE) for 1 and 3. Copper-centered oxidation of 2 and reduction of 3 occur at E1/2 = +0.15 and +0.38 V, respectively. Combined withthe observed Cu(I)-to-pyridine(*) MLCT and pyridine(*)-to-Cu(II) ligand-to-metal charge transfer (LMCT)absorption centered near ~315 nm, the results suggest a mechanism for photo-Bergman cyclization thatis derived from energy transfer to the enediyne unit upon charge-transfer excitation. The intermediatesproduced upon photolysis degrade both pUC19 bacterial plasmid DNA, as well as a 25-base-pair, double-stranded oligonucleotide. Detailed analyses of the cleavage reactions reveal 5'-phosphate and 3'-phosphoglycolate termini that are derived from H-atom abstraction from the 4'-position of the deoxyribosering rather than redox-induced base oxidation.
395 nm) of copper complexes of cis-1,8-bis(pyridin-3-oxy)oct-4-ene-2,6-diyne (bpod, 1), [Cu(bpod)2]PF6 (2), and [Cu(bpod)2](NO3)2 (3) yieldBergman cyclization of the bound ligands. In contrast, the uncomplexed ligand 1 and Zn(bpod)2(CH3COO)2compound (4) are photochemically inert under the same conditions. In the case of 4, sensitizedphotochemical generation of the lowest energy 3-* state, which is localized on the enediyne unit, leadsto production of the trans-bpod ligand bound to the Zn(II) cation by photoisomerization. Electrochemicalstudies show that 1, both the uncomplexed and complexed, exhibits two irreversible waves between Epvalues of -1.75 and -1.93 V (vs SCE), corresponding to reductions of the alkyne units. Irreversible, ligand-based one-electron oxidation waves are also observed at +1.94 and +2.15 V (vs SCE) for 1 and 3. Copper-centered oxidation of 2 and reduction of 3 occur at E1/2 = +0.15 and +0.38 V, respectively. Combined withthe observed Cu(I)-to-pyridine(*) MLCT and pyridine(*)-to-Cu(II) ligand-to-metal charge transfer (LMCT)absorption centered near ~315 nm, the results suggest a mechanism for photo-Bergman cyclization thatis derived from energy transfer to the enediyne unit upon charge-transfer excitation. The intermediatesproduced upon photolysis degrade both pUC19 bacterial plasmid DNA, as well as a 25-base-pair, double-stranded oligonucleotide. Detailed analyses of the cleavage reactions reveal 5'-phosphate and 3'-phosphoglycolate termini that are derived from H-atom abstraction from the 4'-position of the deoxyribosering rather than redox-induced base oxidation.© 2004-2018 中国地质图书馆版权所有 京ICP备05064691号 京公网安备11010802017129号 地址：北京市海淀区学院路29号 邮编：100083 电话：办公室：(+86 10)66554848；文献借阅、咨询服务、科技查新：66554700 |