High Time Resolution Q-Band EPR Study of Sequential Electron Transfer in a Triad Oriented in a Liquid Crystal
| Autor: | Eli Stavitski, Gary P. Wiederrecht, Haim Levanon, Ulrich Heinen, Thomas Berthold, Gerd Kothe, Michael R. Wasielewski, Tamar Galili |
|---|---|
| Rok vydání: | 2001 |
| Předmět: | |
| Zdroj: | The Journal of Physical Chemistry A. 106:1933-1937 |
| ISSN: | 1520-5215 1089-5639 |
| DOI: | 10.1021/jp011805b |
| Popis: | Using high time resolution Q-band EPR we have been able to identify three different radical pairs generated by pulsed laser excitation of the fixed distance triad consisting of a zinc-9-desoxo-meso-methylpyrochlorophyllide donor (ZC), a pyromellitimide primary acceptor (PI), and a naphthalene-1,8:4,5-diimide secondary acceptor (NI), i.e., ZC−PI−NI, oriented in a liquid crystal. Analysis of the transient EPR spectra provides direct evidence for sequential electron transfer from the primary to the secondary radical pair of the triplet channel. At room temperature, this process occurs with an exponential time constant of τT,2 = 50 ± 1 ns. In the singlet-initiated channel, the intramolecular electron-transfer rates are too fast for direct EPR detection. Thus, even the secondary singlet radical pair [ZC•+PINI•-]S is formed instantaneously on the time scale of the EPR experiment. The species decays with a time constant of τS,3 = 36 ± 1 ns by charge recombination to the singlet ground state. The time evolution o... |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|