Water-soluble nile blue derivatives: syntheses and photophysical properties

Article abstract of DOI:10.1002/chem.200801104

Four water-soluble 2-hydroxy-Nile Blue derivatives, 1a, 1b, 2a, and 2b, were prepared by condensation reactions performed under relatively mild conditions (90°C, N,N-dimethylformamide with no added acid). These fluorescent probes had more favorable fluorescence characteristics than two known water-soluble Nile Blue derivatives. Specifically, they were superior to the known dyes with respect to their quantum yields in aqueous media and the sharpness of their fluorescence emissions. Concentration-dependant UV absorption and fluorescence emission studies indicated that the dyes did not aggregate in aqueous solution at concentrations of less than 1-4 μM. The new water-soluble materials 1a, 1b, 2a, and 2b emit in a desirable region of the fluorescence spectrum (A = 670-675 nm). Overall they are potentially interesting for labeling biomolecules in aqueous environments.