INTRAMOLECULAR DEACTIVATION OF PHOTOEXCITED ANTHRACENES BY AROMATIC KETONES

The excited state properties of anthracenes non-conjugatively linked to various types of aromatic ketone were investigated in non-polar solution by determination of the quantum yields of fluorescence and intersystem crossing. In a series of substituted bichromophoric omega-(9-anthryl)propiophenones, the degree of intramolecular fluorescence quenching by the ketone was found to be associated with an increase in the quantum yield of anthracene triplet state formation. Excitation of 4'-piperazinoacetophenone tethered to anthracene resulted in deactivation within the acetophenone chromophore, rather than singlet energy transfer to anthracene. For photoexcited anthracene linked to 2-amido-substituted fluorenone, intramolecular exothermic transfer of the singlet excitation energy to the fluorenone chromophore was found to proceed with high efficiency.