An investigation of the photosensitization of triarylsulfonium salts at wavelengths greater than 400 nm was carried out with phenothiazine and phenoxazine compounds possessing extended benzenoid conjugation. Accordingly, three isomeric benzophenothiazines and 12H-benzo[blphenoxazine were prepared and employed for the photosensitization of several different types of triarylsulfonium salts. These compounds display a tail absorption that extends at least to 450 nm, making them useful for conducting photopolymerizations using long wavelength emission sources. The photosensitized vinyl and ring-opening polymerizations of a number of monomers were conducted and the results are reported in this communication. (C) 2008 Wiley Periodicals, Inc.