Fluorescence "turn-on" sensing of carboxylate anions with oligothiophene-based o-(carboxamido)trifluoroacetophenones

Abstract

o-(Carboxamido)trifluoroacetophenones containing ter- or pentathiophene moiety as a fluorophore exhibit fluorescence enhancement upon binding carboxylate anions. Particularly, the terthiophene derivative shows a large fluorescence enhancement factor (FEF = 120). The enhancement is explained by intramolecular H-bonding stabilization of an anion-ionophore adduct, through which a possible quenching process, the n-pi* transition from the trifluoroacetophenone moiety, is eliminated.