Synthesis and spectral properties of carbazole-coumarin hybrid dyes

In this study, three carbazole-coumarin hybrid dyes were successfully synthesized, and their UV-vis absorption spectra, fluorescence spectra, and structural properties were investigated. The results indicated that diethyl 12-hexyl-2,9-dioxo-9,12-dihydro-2 H -dipyrano[2,3- b :3',2'- h ]-carbazole-3,8-dicarboxylate showed a slight red shift of the maximum absorption wavelength, and its fluorescence intensity was above 4000 arb units, about 22 times higher than that of ethyl 10-hexyl-8-hydroxy-2-oxo-2,10-dihydropyrano[2,3- b ]carbazole-3-carboxylate and ethyl 10-hexyl-8-(hexyloxy)-2-oxo-2,10-dihydropyrano[2,3- b ]carbazole-3-carboxylate in CHCl 3 . The fluorescence intensity of the three compounds first increases and then decreases with the rise of concentration, and the maximum emission wavelength shows a slight red shift. The stability pH range of diethyl 12-hexyl-2,9-dioxo-9,12-dihydro-2 H -dipyrano[2,3- b :3',2'- h ]carbazole-3,8-dicarboxylate in THF was 2–10.