Photochemical dehydrofragmentation reactions: importance of donor and acceptor structure in determination of reactivity in radical ion pairs formed in electron-transfer photoreactions

Journal Article · Wed Nov 11 04:00:00 EST 1987 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00257a066· OSTI ID:6974343

Ci, X; Whitten, D G

Photoinduced electron-transfer reactions are the subject of considerable interest due both to the versatility of net chemical reactions which can be achieved as well as to the variety of intermediates and mechanistic complexities encountered in their study. For initially neutral donors and acceptors quenching of excited singlet states is frequently dominated by formation of a geminate ion pair, A/sup -//D/sup +/, which can subsequently decay by back electron transfer or, in moderately polar to polar solvents, by cage escape to form free ions. In nonpolar solvents the back electron transfer process acts as an effective clock to limit the lifetime for reaction of the geminate pair to the ns time; consequently only relatively rapid reactions can occur efficiently from the geminate pair and these frequently involve participation of the solvent or other reagents present in high concentration. The authors have previously reported the chemically clean and moderately efficient C-C bond photofragmentation reactions of ..beta..-amino-alcohols initiated by electron transfer to excited acceptors. They report here a mechanistic study where this reaction is restricted to the geminate pair and which emphasizes the complimentary roles of reduced acceptor and oxidized donor in facilitating chemical reaction in competition with fast back electron transfer. A key result is that rapid fragmentation is coincident with acceptor radical anion induced deprotonation of the donor cation radical and thus strongly dependent on acceptor structure.

• Research Organization: Univ. of Rochester, NY (USA)
• DOE Contract Number: FG02-86ER13504
• OSTI ID: 6974343
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 109:23; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140505 -- Solar Energy Conversion-- Photochemical
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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
ALCOHOLS
AMINES
BINDING ENERGY
CHEMICAL REACTIONS
DATA
EFFICIENCY
ELECTRON TRANSFER
ELECTRONS
ELEMENTARY PARTICLES
ENERGY
EXPERIMENTAL DATA
FERMIONS
HYDROXY COMPOUNDS
INFORMATION
LEPTONS
NUMERICAL DATA
ORGANIC COMPOUNDS
PHOTOCHEMICAL REACTIONS
POLAR COMPOUNDS
QUANTUM EFFICIENCY
RADICALS
SOLVENTS
TEMPERATURE DEPENDENCE
VALENCE