Other Fluoroionophores with Enhanced Fluorescence in the Presence of Cations

Other Fluoroionophores with Enhanced Fluorescence in the Presence of Cations 

In fac-(bpy)Re(I) (CO)3-A (where bpy is 2,2 -bipyridine and A is an aromatic amine), the d-7t(Re)— jr (bpy) MLCT fluorescent excited state is strongly quenched via intramolecular aniline-Re charge transfer leading to a nonfluorescent LLCT state. By incorporating the donor amino group belonging to the A moiety into a crown-macrocycle, Schanze and Mac Queen(137) have provided a new luminescent cation sensor whose quantum yield of fluorescence raises from 0.0017 (without cation) to 

012 (when Ca2+ is saturated). Emission quantum yield and lifetime data of the complexed probe are interpreted by a kinetic model in which the rate constant of fluorescence and the dissociation of the cation from the macrocycle in the excited state are in competition. 

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