A highly selective fluorescent sensor for fluoride through ESPT signaling transduction

A highly selective fluorescent sensor for fluoride, bis(2-hydroxy-1-naphthaldehyde)-2,6-pyridinedicarboxylic acid hydrazone (H-NP1) was synthesized and structurally characterized. UV-Vis and luminescent titrations of H-NP1 with F− demonstrated the presence of an H-NP1⋯F− interaction species with association constant log K# = 5.26 ± 0.01. The sensor responded to fluoride ion through an excited-state intermolecular proton transfer (ESPT) mechanism with the emission band red-shifted and enhanced. For further studying the potential mechanism, binding-signaling transduction of related compound H-NP2, bis(2-hydroxy-1-naphthaldehyde)-1,3-benzenedicarboxylic acid hydrazone and two control compounds (H-NP3) and (H-NP4) derived from 1-naphthaldehyde was also investigated for comparison.