Electron-Transfer and Acid-Base Properties of a Two-Electron Oxidized Form of Quaterpyrrole that Acts as Both an Electron Donor and an Acceptor
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- 作者：Min Zhang ; Wenbo E ; Kei Ohkubo ; David Sanchez-Garcia ; Dae-Wi Yoon ; Jonathan L. Sessler ; Shunichi Fukuzumi ; Karl M. Kadish
- 刊名：Journal of Physical Chemistry A
- 出版年：2008
- 出版时间：February 21, 2008
- 年：2008
- 卷：112
- 期：7
- 页码：1633 - 1642
- 全文大小：568K
- 年卷期：v.112,no.7(February 21, 2008)
- ISSN：1520-5215
文摘
Electron-transfer interconversion between the four-electron oxidized form of a quaterpyrrole (abbreviated asP4 for four pyrroles) and the two-electron oxidized form (P4H2) as well as between P4H2 and its fully reducedform (P4H4) bearing analogous substituents in the 
- and 
-pyrrolic positions was studied by means of cyclicvoltammetry and UV-visible spectroelectrochemistry combined with ESR and laser flash photolysismeasurements. The two-electron oxidized form, P4H2, acts as both an electron donor and an electron acceptor.The radical cation (P4H2
+) and radical anion (P4H2-) are both produced by photoinduced electron transferfrom dimeric 1-benzyl-1,4-dihydronicotinamide to P4H2, whereas the cation radical form of the compound isalso produced by electron-transfer oxidation of P4H2 with [Ru(bpy)3]3+. The ESR spectra of P4H2+ andP4H2- were recorded at low temperature and exhibit spin delocalization over all four pyrrole units. Thus, thetwo-electron oxidized form of the quaterpyrrole (P4H2) displays redox and electronic features analogous tothose seen in the case of porphyrins and may be considered as a simple, open-chain model of this well-studied tetrapyrrolic macrocycle. The dynamics of deprotonation from P4H2+ and disproportionation of P4H2were examined by laser flash photolysis measurements of photoinduced electron-transfer oxidation and reductionof P4H2, respectively.
- and -pyrrolic positions was studied by means of cyclicvoltammetry and UV-visible spectroelectrochemistry combined with ESR and laser flash photolysismeasurements. The two-electron oxidized form, P4H2, acts as both an electron donor and an electron acceptor.The radical cation (P4H2+) and radical anion (P4H2-) are both produced by photoinduced electron transferfrom dimeric 1-benzyl-1,4-dihydronicotinamide to P4H2, whereas the cation radical form of the compound isalso produced by electron-transfer oxidation of P4H2 with [Ru(bpy)3]3+. The ESR spectra of P4H2+ andP4H2- were recorded at low temperature and exhibit spin delocalization over all four pyrrole units. Thus, thetwo-electron oxidized form of the quaterpyrrole (P4H2) displays redox and electronic features analogous tothose seen in the case of porphyrins and may be considered as a simple, open-chain model of this well-studied tetrapyrrolic macrocycle. The dynamics of deprotonation from P4H2+ and disproportionation of P4H2were examined by laser flash photolysis measurements of photoinduced electron-transfer oxidation and reductionof P4H2, respectively.