FLUORESCENT MOLECULAR PROBES .2. THE SYNTHESIS, SPECTRAL PROPERTIES AND USE OF FLUORESCENT SOLVATOCHROMIC DAPOXYL(TM) DYES

2,5-Diphenyloxazoles that embody a dimethylamino group at position 4 o f the 5-phenyl ring and a sulfonyl group at position 4 of the 2-phenyl ring were prepared as new fluorescent solvatochromic dyes, In these m olecules, there is a ''push-pull'' electron transfer system from the 5 -phenyl moiety to the 2-phenyl ring, These compounds show strong solve nt-dependent fluorescence that is well correlated with the empirical s olvent polarity parameter E-T (30). The solvent polarity dependence su ggests that the fluorescence arises from an intramolecular charge tran sfer. The fluorescence-environment dependence, long emission wavelengt h, large extinction coefficients, high fluorescence quantum yields and large Stokes shift of the fluorophores can be used to develop ultrase nsitive fluorescent molecular probes to study a variety of biological events and processes.