Bichromophoric fluorescent dyes with rigid molecular structure: fluorescence ability regulation by the photoinduced intramolecular electron transfer

Bichromophoric 3-diethylamino-7-phenyl-7H-benzo-[4,5]-imidazo-[1,2-c]-chromeno-[3,2-e]-pyrimidines were synthesized by the condensation of 7-diethylamino-3-(2-benzimidazolyl)-iminochromene with several aromatic aldehydes. Fluorescence properties of these compounds were studied in solvents of various polarity and acidity. The excited state intramolecular electron transfer was shown as the reason for the fluorescence quenching of the studied dyes with electron donor substituents in the minor chromophoric moiety. Prospects for the usage of these compounds as fluorescence probes sensitive to polarity and pH of their surrounding were elucidated.