No abstract

A new polymer and small molecules containing the chromophore bis(2-(4-pyridiniumyl)thiazole) were synthesized. Their tetraphenylborate salts showed absorption spectral changes in the visible to near-infrared region accompanying a colour change from yellow to green on steady photoirradiation. From electron spin resonance measurements and comparison with Molecular Orbital PACkage (MOPAC) calculations, this was assigned to the formation of bis(2-(4-pyridiniumyl)thiazole) radicals due to a photoinduced electron-transfer reaction from tetraphenylborate and decomposition of its oxidized form. Transient absorption spectra corresponding to those of tetraphenylborate salts were observed for bromide salts on femtosecond laser excitation of the polymer in solid films and solutions. The fastest decay of transient absorption due to back electron transfer was less than 1 picosecond.