Photochemistry of cerium(IV) ammonium nitrate (CAN) in acetonitrile

• Mechanism of cerium(IV) ammonium nitrate (CAN) photolysis in CH 3 CN is presented. • Inner-sphere electron transfer was found to be the primary photochemical process. • High quantum yield of NO 3 formation (0.6 and 0.4 upon 308 and 355 nm excitation). • Rate constants of reactions responsible for NO 3 decay are measured. • A part of excited CAN molecules form the radical complex [(NH 4 ) 2 Ce III (NO 3 ) 5 …NO 3 ]. Cerium ammonium nitrate (NH 4 ) 2 Ce IV (NO 3 ) 6 (CAN) is widely used as a photolytic source of NO 3 radicals in acetonitrile. In spite of that, the mechanistic aspects of CAN photochemistry were poorly discussed in the literature. In this work CAN photochemistry in CH 3 CN was studied using the combination of stationary methods and laser flash photolysis. In accordance with the literature, the inner-sphere electron transfer was found to be the primary photochemical process. The (NH 4 ) 2 Ce III (NO 3 ) 5 (CH 3 CN) complex was found to be the only reaction product formed with the rather high quantum yield (0.6 and 0.4 upon 308 and 355 nm excitation correspondingly). The NO 3 radicals decay is mainly caused by the second-order reactions; their rate constants are determined. In addition to the direct release of the NO 3 radicals, a part of the light-excited CAN molecules were found to form the radical complex [(NH 4 ) 2 Ce III (NO 3 ) 5 …NO 3 ], which lifetime is ca. 2 μs.