Photophysics and photochemistry of 4-Dihydropyridinones

Dihydropyridinones (DHP) react photochemically with olefins to form cycloaddition products. The reactions proceed through the lowest excited state T, of the DHPs, with rate constants which depend on the olefin and can approach the diffusional limit in the most favourable cases. Intra- and inter-molecular sensitization and quenching have been investigated, as well as spectroscopic properties such as absorption and luminescence spectra, and in particular electron energy loss spectra which have established the energy of the reactive T, state as 295 kJ mol"' (3.07 eV).