New 2,2′:6′,2′′-terpyridines as colorimetric and fluorescent sensors for fluoride ions

Abstract

Two new 2,2′:6′,2′′-terpyridine receptors bearing phenol groups, 1 and 2, have been prepared by coupling 4′-(4-aminophenyl)-2,2′:6′,2′′-terpyridine with salicylaldehyde or 4-hydroxybenzaldehyde. Both receptors show colorimetric and fluorescent response to F⁻ over other anions in organic solvent. In addition, a strong intramolecular N⋯H–O hydrogen bond was found in 1, which is attributed to its weaker binding ability to F⁻ than that of 2, and an Excited-State Intramolecular Proton Transfer (ESIPT) emission quenching process.