Detection of Amine Vapors using Luminescent Xerogels from Supramolecular Metal-Containing Gelator

Supramolecular fluorescent gelators containing a tris(β-diketonato) complex are synthesized by using gelation-driving chelates, and their gelation abilities are studied with 15 solvents. Thin-layer films are prepared on quartz plates from the solutions and they are studied as chemosensors for amines. Fluorescence-quenching of the thin-layer films upon exposure to saturated primary and secondary amine vapors is monitored to evaluate the abilities of the chemosensors to detect amines. The morphologies of the thin-layer films are observed by transmission electron microscopy (TEM) and discussed in relation to their fluorescence-quenching. The fluorescence-quenching efficiencies upon exposure to saturated primary and secondary amines depend on the basicity and bulkiness of the amines rather than the vapor pressure. The fluorescence-quenching is caused by decomposition of a complex through nucleophilic addition of primary or secondary amines to its carbonyl group. The detection of tertiary amines is performed by monitoring the fluorescence emission from the thin-layer films, which are composed of a ligand and EuCl3. The emergence of fluorescence originates from the formation of fluorescent Eu3+-containing gelator, in which dehydrochloric acid by tertiary amines is a trigger for the complexation.