Fluorescence characteristics of ionic benzofurazans, 7-substituted-2,1,3-benzoxadiazole-4-sulfonates

Hydrophilic fluorescent derivatization reagents, sensors and probes are of great value because of their use in accurate analyses under water-rich condition. In this study, 13 7-substituted-2,1,3-benzoxadiazole-4-sulfonates (called SBD derivatives) as representatives of ionic benzofurazans were synthesized and their absorption and fluorescence spectra were obtained in solvents of varying polarity. The fluorescence quantum yields (Φf) of the investigated compounds were significantly affected by the substituent at the 4-position. Solvent effects on the Φf values were also observed. It was found that the combination of the PM3 and PM3-CAS/CI (CI = 6) methods afforded a good relationship between the experimental and calculated S1 ← S0 transition energies of the SBD derivatives.