INTRAMOLECULAR DEACTIVATION OF PHOTOEXCITED ANTHRACENES BY AROMATIC KETONES

The excited state properties of anthracenes non-conjugatively linked t o various types of aromatic ketone were investigated in non-polar solu tion by determination of the quantum yields of fluorescence and inters ystem crossing. In a series of substituted bichromophoric omega-(9-ant hryl)propiophenones, the degree of intramolecular fluorescence quenchi ng by the ketone was found to be associated with an increase in the qu antum yield of anthracene triplet state formation. Excitation of 4'-pi perazinoacetophenone tethered to anthracene resulted in deactivation w ithin the acetophenone chromophore, rather than singlet energy transfe r to anthracene. For photoexcited anthracene linked to 2-amido-substit uted fluorenone, intramolecular exothermic transfer of the singlet exc itation energy to the fluorenone chromophore was found to proceed with high efficiency.