Photoaddition of the charge-transfer complexes of 7,7,8,8-tetracyanoquinodimethane–toluene systems

Abstract

A novel photo-induced addition via charge-transfer excitation is described. Irradiation of a toluene solution of 7,7,8,8-tetracycnoquinodimethane gave α,α-dicyano-4-dicyanomethylbibenzyl. p-Xylene underwent similar addition on irradiation of its charge-transfer absorption band. The reaction was accelerated by the presence of trifluoroacetic acid or methanol, indicating the participation of a proton-transfer step. The yields of the photoadducts were increased at higher temperatures. A mechanism involving an electron-transfer followed by a protontransfer is proposed.