Anion Sensing with Luminescent Tris(β-diketonato)europium(III) Complexes and Naked-Eye Detection of Fluoride Anion

Four kinds of tris(β-diketonato)europium(III) complexes were demonstrated to form highly coordinated complexes with inorganic anions and to exhibit anion-dependent luminescence. Their luminescence profiles were significantly dependent on the natures of β-diketonato ligands and external coordinative anions: Tris[3-(heptafluorobutyryl)-2-bornanonato]europium(III) complex gave F− anion-enhanced luminescence, and tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octadionato)europium(III) complex responded to HSO4− and CH3CO2− anions. Although the employed europium complexes included similar β-diketonato ligands, UV and IR characterizations and luminescence lifetime measurements revealed that the structure of the β-diketonato ligand had significant influences on anion coordination and sensing behaviors of the europium complex. Since the observed anion-enhanced luminescence was high enough to be detected by the naked eye, visual detection of the F− anion in an aqueous sample was realized with the tris[3-(heptafluorobutyryl)-2-bornanonato]europium(III) complex.