Photophysics of novel 2,6-disubstituted benzobisthiazoles possessing chromophoric groups

Abstract

A series of 2,6-disubstituted benzo[1,2-d:4,5-d′]bisthiazoles that have two photofunctional groups was synthesized, and their absorption and emission spectra in chloroform solution were examined. An anthracene derivative, 2,6-di(9-anthryl)benzo[1,2-d:4,5-d′]bisthiazole (DABBT), as well as a mono-substituted compound, 2-(9-anthryl)benzothiazole (ABT), showed a broad emission band at a long wavelength without any monomer emission of an anthryl group even for a concentration as low as 5 × 10⁻⁷ M. In contrast, naphthalene derivatives, 2,6-di(1-naphthyl)benzo[1,2-d:4,5-d′]bisthiazole (D1NBBT) and 2,6-di(2-naphthyl)benzo[1,2-d:4,5-d′]bisthiazole (D2NBBT), showed entirely monomer emission of a naphthyl group with no broad emission band at longer wavelengths. The broad emission bands observed for DABBT and ABT are attributed to an excited charge-transfer state in which an electron has transferred from a benzothiazole unit to an anthryl group.