Photochemical properties of 4-benzoylbenzylammonium borates

Several new 4-benzoylbenzylammonium berates were prepared in order to study their photochemical properties. It was found that a quantitative yield of biphenyl and a small amount of benzene are formed from photolysis of the ti tle compounds as tetraphenylborates in the absence of oxygen. In addition, amines and methylbenzophenone were detected after the steady-state photolys is. The quantum yields of the photolysis of the title compounds and the for mation of biphenyl, amines, and methylbenzophenone were determined. Radical trapping experiments showed that the photogenerated amine is converted to an a-aminoalkyl radical, which is an important initiating species for the p olymerization of acrylates when tetraphenylborate is chosen as a counterani on. It was found that even 1-(4-benzoylbenzyl)pyridinium tetraphenylborate is an active photoinitiator, however, indicating that a-aminoalkyl radical is not the only initiating species formed from 4-benzoylbenzylammonium tetr aphenylborates. The effect of structure on initiating activity was determin ed and discussed.