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 pr epared by condensation of hydroxy- and methanesulfonamidoterephthalic acids with 2-aminophenols. These displayed excited state intramolecula r proton-transfer fluorescence at room temperature and above with quan tum yields as high as 0.48 and emission peaks of 492-517 nm. The metha nesulfonamido group was found about as effective a proton donor as the phenolic hydroxyl group. Incorporation of substituents onto the benzo xazole moieties increased solubility of the fluors in hydrocarbon solv ents in some cases, but reduced quantum yields. These fluors arc of in terest as wavelength shifters in a scintillating detecting medium for ionizing radiation,