Copper(II)-directed static excimer formation of an anthracene-based highly selective fluorescent receptor

A novel 'turn-on' fluorescent receptor methyl 3-((anthracen-9-ylmethylene)amino)benzoate (MAB) with anthracene as the fluorophore and methyl 3-aminobenzoate as a metal ion chelating center has been designed and synthesized. The ability of the prepared receptor to detect metal ions has been evaluated by the changes in its emission intensity. MAB demonstrates high selectivity and sensitivity for Cu2+ among the nineteen metal ions examined in MeCN. The interaction of MAB with Cu2+ causes a significant enhancement in emission intensity due to the combination of a unique anthracenyl static excimer formation, the restricted CN isomerization and the suppression of highly efficient photoinduced electron transfer (PET) process. The disassociation of the excimer species to monomers is directed by temperature, Cu2+ concentration and solvent fraction. Furthermore, the considerable 'off-on' fluorescence response or the conversion of the excimer species to monomers concomitantly led to the apparent color changes, which could also be identified easily by the naked eye using a UV lamp.