Photochemistry and photophysics of (p-benzoylphenyl)diphenylmethyl and (p-benzoylphenyl)bis(4-tert-butylphenyl) radicals in different solvents

The photochemical reactions of (p-benzoylphenyl)diphenylmethyl (1) and (p-b enzoylphenyl)bis(4-tertbutylphenyl)methyl (2) in various solvents were inve stigated. The photophysical parameters of the first excited doublet state o f the radicals were measured using spectroscopic and kinetic methods and le d to a "molecular rotor" model to characterize the excited-state behavior. The charge-transfer excited state for both radicals was observed. Photoprod ucts separated from the photolysis of 1 and 2 in benzene suggest photodecom position proceeds via H-abstraction (55%), fragmentation (20%), cyclization (10%), and addition (10%).