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Communication

Unusual Role of Oxygen in Electron-Transfer Processes

Sergei Smirnov,*^† Ivan Vlassiouk,^† Olaf Kutzki,^†^‡ Michael Wedel,^‡ and Franz-Peter Montforts^‡

Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, New Mexico, and Universität Bremen, Institut für Organische Chemie, Leobener Strasse NW2, 28359 Bremen, Germany

J. Am. Chem. Soc., 2002, 124 (16), pp 4212–4213

DOI: 10.1021/ja017616o

Publication Date (Web): March 28, 2002

To whom correspondence should be addressed. E-mail: snsm@nmsu.edu.

†

New Mexico State University.

‡

Universität Bremen.

‖

Present address: Duke University, Department of Chemistry, LSRC, Suite A005, Box 90317, Durham, NC 27708; e-mail: mwedel@chem.duke.edu.

Abstract

Molecular oxygen's unique involvement in electron-transfer processes is demonstrated on a series of dyads between porphyrin derivatives and fullerene C₆₀. It has been shown for the first time that oxygen can serve as an inhibitor of back electron transfer by enhancing intersystem crossing of a singlet radical ion pair into its triplet state. The effect is observed only when energy of the charge-separated state is lower than that of the locally excited triplet states. Due to the spin statistics, the reverse intersystem crossing is less efficient, allowing use of oxygen and other paramagnetic species for impeding charge recombination in various electron-transfer systems.

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