Hexaamide Molecule Annexed with Pyrenes for Selective Detection of Phosphate and Pyrophosphate Ions by Ratiometric Fluorescence Changes

Abstract

AbstractN,N′‐bis{3,5‐di[(1‐pyrenylmethyl)carbamoyl]benzyl}pyridine‐2,6‐dicarbamide (compound 1) provides a pseudo‐tetrahedron cleft and multiple hydrogen bondings to form a 1:1 complex with phosphate (or pyrophosphate) ion in a highly selective manner, in comparison with other anions (F−, Cl−, Br−, SCN−, AcO−, NO3−, and ClO4−). Compound 1 bears four pyrene rings as the sensitive fluorescent readout unit for phosphate and pyrophosphate ions. The binding strength can be inferred from the emission intensity ratio of the pyrene monomer (λmax = 377 nm) to the excimer (λmax ˜ 480 nm). The enhanced multiple hydrogen bondings and ratiometric sensing mechanism render an opportunity for sensing pyrophosphate ion at micromolar concentration, even in water‐containing solution. The binding model is supported by fluorescence and 1H NMR studies.