Picosecond kinetics of state-selective singlet oxygen producing photochemistry of aromatic endoperoxides

Abstract

Picosecond measurements show that the photo-fragmentation of anthracene endoperoxides leading to the anthracene moiety and singlet oxygen does not occur in a single step, but involves a short-lived intermediate. The upper excited state dual bond dissociation kinetics of the endoperoxides of 9,10-diphenylanthracene (9,10-DPA-O 2) and of 9-phenylanthracene (9,10-PA-O 2) were measured. For 9,10-DPA-O 2 the ground state aromatic appears in 95 ± 10 ps, whereas for 9,10-PA-O 2 it appears in 60 ± 7 ps. The results are consistent with our earlier proposed mechanism for the dissociation from the upper excited singlet states of isomers of the anthracene endoperoxides.