Spectroscopic properties of push-pull 2-(4-carboxyphenyl)-6-dimethylaminobenzothiazole derivatives in solution and the solid state

Abstract 6-Dimethylamino-2-phenylbenzothiazoles with a carboxy, ester and amide substituent on the 2-phenyl group were prepared as a series of the push-pull benzothiazoles, and their spectroscopic and photophysical properties in solutions were investigated. The derivatives showed solvatochromic fluorescence with quantum yields over 0.68 in various organic solvents similar to the core fluorophore structure. The color variation ranges in fluorescence solvatochromism of the derivatives were wider than that of the original compound having the core structure, 6-dimethylamino-2-phenylbenzothiazole. It was also found that the derivatives together with the original compound show solid state fluorescence depending on their crystal structures. In particular, an ester derivative with a protected serine has a reasonable crystal packing leading to increase in fluorescence efficiency. The results of the present study provide a guide to design push-pull 2-phenylbenzothiazoles exhibiting fluorescence in solution and the solid state.