Photo-retro-DielsAlder (PrDA) reactions of a variety of
DielsAlder (DA) adducts were studied. Experimental results showed that
the photoreactivity (quantum yield) depends on the electron-donating
ability of the diene component and the electron-withdrawing ability of the
dienophile component. The mechanism was studied by trapping the reaction
intermediate, O2
quenching, time-resolved absorption, and fluorescence
spectroscopy. All the results support a mechanism that involves a chargeseparated intermediate generated from a singlet excited state. The PrDA
reaction may find applications in photoresponsive materials, photolithography, drug delivery, and mechanistic research.