PHOTOCHEMISTRY OF SQUARAINE DYES .8. PHOTOPHYSICAL PROPERTIES OF CROWN-ETHER SQUARAINE FLUOROIONOPHORES AND THEIR METAL-ION COMPLEXES

The photophysical properties of a series of red-sensitive, highly fluo rescent bis[4-(monoaza-crown ether)phenyl]squaraine fluoroionophores a re reported. These dyes are soluble in both polar and nonpolar solvent s with fluorescence quantum yield varying from 0.01 to 0.85. These dye s readily form aggregates in aqueous solutions. These aggregates disso ciate in beta-cyclodextrin solutions as the dye molecules form 1:1 com plex with beta-cyclodextrin. This complexation process is accompanied by a significant enhancement in the fluorescence yields of these dyes. Complexation of the fluoroionophores with alkali-metal ions brings ab out drastic reductions in their fluorescence quantum yield as well as significant changes in their redox properties.