A colorimetric chemosensor for the rapid detection of acetate anion and neutral molecules in water

Molecular recognition of anions or neutral molecules in water by artificial probes remains a challenging yet vibrant area in supramolecular chemistry. Herein, we report a novel colorimetric probe based on a phenolphthalein scaffold. This probe exhibits excellent sensitivity toward acetate and various organic solvents in pure water, with a distinct colorimetric response. UV–vis titration experiments revealed a high binding affinity for acetate (β2 ≈ 3.3 × 106 M-2) and weaker affinities for solvents (0.1–1159 M-2). Notably, a correlation between solvent binding strength and lipophilicity (logP) is observed for the first time: for solvents with negative logP, the affinity increases as lipophilicity decreases. Mechanistic studies suggest a hydrogen bond induced proton transfer (HBPT) process, wherein an intramolecular O···H–N hydrogen bond and the tautomeric properties of the phenolphthalein moiety play key roles. This work introduces a new design strategy for artificial probes capable of rapid and selective detection of both charged and neutral species in aqueous media.