Abstract: Three novel asymmetric trimethine benzothiazole cyanine dyes with different N-substituents were designed and synthesized. The structures of the dyes were characterized, and the maximums of the spectral absorption and emission of the dyes in ethanol were found in the range of 629~635 nm and 656~672 nm. The Stokes shift values for dyes 8, 9 and 10 were 23, 37 and 27 nm, respectively. The dyes were almost non-fluorescent in solvents with a low fluorescent quantum yield of less than 0.021 in ethanol, which could reduce the background interference greatly. The photodegradation experiment showed that the introduction of benzyl group on the heteroaromatic rings improved the photostabilites of the dyes obviously. The oxidizing potentials for the dyes 8, 9 and 10 were at 0.535, 0.456 and 0.399 V vs SCE, which was consistent with the data of photodegradation experiment.

Key words: Benzothiazole cyanine dye, Nucleic acid probe, photodegradation, cyclic voltammogram, Disease diagnosis