Fluorescence Perturbation in an Anthlylazamacrocycle CHEF Sensor

Chelatoselective Fluorescence Perturbation in an Anthlylazamacrocycle CHEF Sensor 

In addition to a fluorescence perturbation, the Cd(II)-5d combination also uniquely yields aperturbation in the ultraviolet (UV) spectrum. A difference spectrum obtained by subtracting a fractional amount of an uncomplexed 5d spectrum from the perturbed spectrum is the mirror image of a fluorescence difference spectrum obtained by similar means. Moreover, excitation at 400 nm (where 1-4 are weakly absorbing but where moderate absorption is seen in the difference spectrum) gives rise to an emission spectrum with identical shape and Amax (456 nm) to that of the fluorescence difference spectrum. Thus, evidence points to the existence of two equilibrating ground state species as the physical basis for the chelatoselective emission. Bouas-Laurent has reported a related observation in methanol where a red-shifted CHEF was observed for a T1(I) 7r-complex.(14) 

The observed fluorescence, UV, and H NMR perturbations of the Cd(II)-5d complex are observed only in water in methanol, ethanol, and acetonitrile only unperturbed anthracenic spectra are observed. 

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