High time resolution Q-band EPR study of sequential electron transfer in a triad oriented in a liquid crystal

Ulrich Heinen, Thomas Berthold, Gerd Kothe, Eli Stavitski, Tamar Galili, Haim Levanon, Gary Wiederrecht, Michael R Wasielewski

Research output: Contribution to journalArticle

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Abstract

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-methylpyrochloro-phyllide 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 of the transverse magnetization exhibits fast initial oscillations, which disappear 50 ns after the laser pulse. Model calculations indicate that these oscillations can be assigned to zero quantum electron precessions in [ZC.+PINI.-]s. Thus, for the first time, quantum beats have been observed from a spin-correlated radical pair, oriented in a liquid crystal.

Original languageEnglish
Pages (from-to)1933-1937
Number of pages5
JournalJournal of Physical Chemistry A
Volume106
Issue number10
DOIs
Publication statusPublished - Mar 14 2002

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Liquid Crystals
Paramagnetic resonance
electron transfer
liquid crystals
Electrons
time constant
oscillations
Laser excitation
Theophylline
Pulsed lasers
precession
naphthalene
Ground state
Zinc
Laser pulses
synchronism
Magnetization
pulsed lasers
zinc
magnetization

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

High time resolution Q-band EPR study of sequential electron transfer in a triad oriented in a liquid crystal. / Heinen, Ulrich; Berthold, Thomas; Kothe, Gerd; Stavitski, Eli; Galili, Tamar; Levanon, Haim; Wiederrecht, Gary; Wasielewski, Michael R.

In: Journal of Physical Chemistry A, Vol. 106, No. 10, 14.03.2002, p. 1933-1937.

Research output: Contribution to journalArticle

Heinen, U, Berthold, T, Kothe, G, Stavitski, E, Galili, T, Levanon, H, Wiederrecht, G & Wasielewski, MR 2002, 'High time resolution Q-band EPR study of sequential electron transfer in a triad oriented in a liquid crystal', Journal of Physical Chemistry A, vol. 106, no. 10, pp. 1933-1937. https://doi.org/10.1021/jp011805b
Heinen, Ulrich ; Berthold, Thomas ; Kothe, Gerd ; Stavitski, Eli ; Galili, Tamar ; Levanon, Haim ; Wiederrecht, Gary ; Wasielewski, Michael R. / High time resolution Q-band EPR study of sequential electron transfer in a triad oriented in a liquid crystal. In: Journal of Physical Chemistry A. 2002 ; Vol. 106, No. 10. pp. 1933-1937.
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