SYNTHESIS AND PHOTOPHYSICAL PROPERTIES OF FLUORESCENT 2,5-DIBENZOXAZOLYLPHENOLS AND RELATED-COMPOUNDS WITH EXCITED-STATE PROTON-TRANSFER

A series of new 2,5-dibenzoxazolylphenols and related compounds was prepared by condensation of hydroxy- and methanesulfonamidoterephthalic acids with 2-aminophenols. These displayed excited state intramolecular proton-transfer fluorescence at room temperature and above with quantum yields as high as 0.48 and emission peaks of 492-517 nm. The methanesulfonamido group was found about as effective a proton donor as the phenolic hydroxyl group. Incorporation of substituents onto the benzoxazole moieties increased solubility of the fluors in hydrocarbon solvents in some cases, but reduced quantum yields. These fluors arc of interest as wavelength shifters in a scintillating detecting medium for ionizing radiation,