Selective recognition of oxalate in water: effect of pH on binding strength and sensing mechanisms.

Bicyclic receptors bearing anthracene as a strap were designed for selective oxalate binding in a buffered aqueous solution. The receptors were found to possess two mechanisms of fluorescence response depending on the pH of a buffered solution. Receptor 2 binds oxalate at pH 6.2 showing a 10-fold fluorescence enhancement and a two orders of magnitude selectivity over other anions.