Adiabatic and Charge-Transfer Pathways in the Photocleavage of Dimers and Cycloadducts of Some Aromatic Molecules

Article abstract of DOI:10.1021/ja00231a028

The photocycloreversion of the 9-cyanoanthracene (CA) 4 + 4 dimer and of the cycloadducts between CA and anthracene, CA and 2-methylnaphthalene, and anthracene and 2-cyanonaphthalene was investigated at room temperature.This process is essentially adiabatic for the two anthracene-naphthalene cycloadducts and > 90 percent diabatic for anthracene-anthracene cycloadducts.A rationalization is offered on the basis of the correlation diagrams for cycloaddition and is supported by quantum yield and fluorescence studies of both photocycloaddition and cycloreversion.A charge-transfer pathways becomes competitive in polar solvents in both reactions.