Photochemical C–P Bond Cleavage of Nitrobenzylphosphonate Ions

Abstract
Upon UV-irradiation, the C–P bond of p-nitrobenzylphosphonate ions cleaved with a quantum yield of about 0.7 in an aqueous alcohol solution to give 1,2-bis(4-nitrophenyl)ethane, p-nitrotoluene, orthophosphate, and alkyl dihydrogenphosphate. Whereas in an aqueous solution 1,2-bis(4-nitrophenyl)ethane was produced as a main product, in an alcohol solution only p-nitrotoluene was produced. This photolysis may proceed via intramolecular electron transfer from PO32− group to nitro aromatic moiety to form an excited state, which undergoes C–P bond cleavage to give p-nitrobenzyl anion and monomeric metaphosphate anion as intermediates. The C–P bond cleavage of p-nitrobenzylphosphonate ion occurred more readily than those of o- and m-nitrobenzylphosphonate ions.