Naked-Eye Detection of C1–C4 Alcohols Based on Ground-State Intramolecular Proton Transfer

Previous reports of fluorescent sensors for alcohols based on charge-transfer character of their excited state are based on mono-, di-, and tetra-phosphonate cavitands, which are capable of selecting analytes through shape/size selection and various specific H-bonding, CH−π, and cation–dipole interactions. To contrast, color changes based on absorption properties of the ground state are more suitable for direct observation with the naked eye. Three sensitive and selective colorimetric sensors for C1–C4 alcohols have been developed on the basis of alcohol-mediated ground-state intramolecular proton transfer. Reverse proton transfer induced by water achieves a fully reversible reaction. In addition, the solvent color indicates alcohol concentration.