Highly efficient and selective turn-off quenching of ligand-sensitized luminescence from europium imidazo[4,5-f]-1,10-phenanthroline complex by fluoride ion

A smart fluoride sensitive luminescence probe based on 1:2 complex of europium(III) with 2-(2-hydroxyphenyl)imidazo[4,5-f]-1,10-phenanthroline was prepared. The emission of europium ions via photosensitization of the ligand was completely quenched by addition of 2 equiv. of fluoride ions in DMSO. Spectroscopic analyses proved that the imidazolyl NH of the ligand was hydrogen-bonded with additive fluoride to form the 1:1 complex, leading to suppression of the photosensitization.