Mechanism of chelation enhanced fluorescence in complexes of cadmium(II), and a possible new type of anion sensor

The Cd(II) complex of adpa (N-(9-anthracenylmethyl)-N,N-di-(picolyl)amine) in MeOH-H2O has increased fluorescence intensity with [Cl-], a new type of anion sensor. The structure of [Cd(adpa)(NO3)(2)] has a proposed fluorescence-quenching pi-contact between Cd and the fluorophore, while the Cl in [Cd(adpa)Cl-2] disrupts the pi-contact, restoring fluorescence.