Variations in mechanism for photoinduced valence isomerizaation of an electron-donor nonconjugated diene

Journal Article · Wed Mar 09 04:00:00 EST 1983 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00343a032· OSTI ID:5554970

Jones, G II; Becker, W G; Chiang, S H

Photoisomerization of 1,4,4a,8,8a-hexahydro-1,4,5,8-endo,endo-dimethanonaphthalene (3) has been studied in detail. Rearrangement to the cage photoisomer occurs on direct irradiation or with triplet sensitizers with quantum efficiency as high as 1.0. Irradiation in the presence of electron acceptors whose fluorescence is quenched by 3 also results in cage formation. Quantum yields approach 1.0 for donor-acceptor sensitization in a nonpolar solvent. For this reaction, a mechanism is proposed that involves excitation transfer within an exciplex of sensitizer and 3 and partitioning of locally excited 3 at a biradicaloid geometry. Quantum efficiencies exceed unity for rearrangement sensitized by electron acceptors in polar media. A chain mechanism is proposed that involves radical-cation intermediates obtained through electron transfer from 3. Irradiation of ground-state (charge-transfer) complexes of 3 and fumaronitrile or diethyl 1,2-dicyanofumarate also results in valence isomerization with quantum yields that are dependent on solvent polarity and excitation wavelength. The options available for photosensitization of 3 and a related diene, norbornadiene, are discussed.

• Research Organization: Boston Univ., MA
• OSTI ID: 5554970
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 105:5; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
AROMATICS
CHEMICAL REACTIONS
CONDENSED AROMATICS
DIENES
EFFICIENCY
ELECTRON TRANSFER
ENERGY LEVELS
EXCITED STATES
FLUORESCENCE
HYDROCARBONS
IRRADIATION
ISOMERIZATION
LUMINESCENCE
NAPHTHALENE
ORGANIC COMPOUNDS
POLYENES
QUANTUM EFFICIENCY
QUENCHING
STRUCTURAL CHEMICAL ANALYSIS