Highly selective fluorescence sensors for the fluoride anion based on carboxylate-bridged diiron complexes

A new ligand bearing anthracene and its Fe(III) and Ru(III) derivatives have been synthesized and characterized exactly. The studies show that these dinuclear metal complexes serve as candidates of fluorescence chemosensors for anions. The interactions between these complexes and anions have been investigated by means of UV-Vis absorption spectra, fluorescence spectra, titration studies and 1H-NMR. The results illustrated that two diiron complexes, [Cp*Fe(μ-SR)2(μ-η2-L)FeCp*][PF6] (5a, R = Me; 5b, R = Et; L = 4-(3-(anthracen-9-ylmethyl)ureido)benzoate), showed rapid and selective recognition for the fluoride ion over other anions with strong enhancement of emission intensities. The sensing mechanisms indicate that the hydrogen bonding interaction has been observed between chemosensors and F−.