Quinoxalino[2,3-b']porphyrins Behave as -Expanded Porphyrins upon One-Electron Reduction: Broad Control of the Degree of Delocal
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- 作者：Karl M. Kadish ; Wenbo E ; Paul J. Sintic ; Zhongping Ou ; Jianguo Shao ; Kei Ohkubo ; Shunichi Fukuzumi ; Linda J. Govenlock ; James A. McDonald ; Andrew C. Try ; Zheng-Li Cai ; Jeffrey R. Reimers ; Maxwell J. Cr
- 刊名：Journal of Physical Chemistry B
- 出版年：2007
- 出版时间：August 2, 2007
- 年：2007
- 卷：111
- 期：30
- 页码：8762 - 8774
- 全文大小：547K
- 年卷期：v.111,no.30(August 2, 2007)
- ISSN：1520-5207
文摘
The synthesis and redox properties of a series of free-base and metal(II) quinoxalino[2,3-b']porphyrins andtheir use in an investigation of the substituent effects on the degree of communication between the porphyrinand its 
,'-fused quinoxalino component are reported. ESR, thin-layer spectroelectrochemistry, and quantumchemical calculations of the resultant radical anions from one-electron reduction indicate that localization ofthe unpaired electron across both the porphyrin and the fused quinoxalino group can be controlled, the systemas a whole behaving as a highly polarizable 
-expanded porphyrin radical anion. ESR studies on the radicalanions of zinc(II) quinoxalino[2,3-b']porphyrin derivatives indicate that nitrogen-atom spin distribution changesas a function of chemical substitution: 27% quinoxaline character when the porphyrin ring bears a 7-nitrosubstituent, 34% quinoxaline character in the unsubstituted parent, and 51-61% nitroquinoxaline characterwhen the quinoxalino unit has one or more nitro groups. Close analogies are found between the calculatedand observed nitrogen-atom spin distributions, indicating that the calculations embody the key chemical effects.The calculations also indicate that the nitrogen-atom spin distributions closely parallel the important totalporphyrin, quinoxaline, and nitro spin distributions, indicating that the observed quantities realistically depictthe change in the nature of the delocalization of the radical anion as a function of chemical substitution. Theprofound effects observed indicate long-range communication of the type that is essential in molecularelectronics applications.
,'-fused quinoxalino component are reported. ESR, thin-layer spectroelectrochemistry, and quantumchemical calculations of the resultant radical anions from one-electron reduction indicate that localization ofthe unpaired electron across both the porphyrin and the fused quinoxalino group can be controlled, the systemas a whole behaving as a highly polarizable -expanded porphyrin radical anion. ESR studies on the radicalanions of zinc(II) quinoxalino[2,3-b']porphyrin derivatives indicate that nitrogen-atom spin distribution changesas a function of chemical substitution: 27% quinoxaline character when the porphyrin ring bears a 7-nitrosubstituent, 34% quinoxaline character in the unsubstituted parent, and 51-61% nitroquinoxaline characterwhen the quinoxalino unit has one or more nitro groups. Close analogies are found between the calculatedand observed nitrogen-atom spin distributions, indicating that the calculations embody the key chemical effects.The calculations also indicate that the nitrogen-atom spin distributions closely parallel the important totalporphyrin, quinoxaline, and nitro spin distributions, indicating that the observed quantities realistically depictthe change in the nature of the delocalization of the radical anion as a function of chemical substitution. Theprofound effects observed indicate long-range communication of the type that is essential in molecularelectronics applications.