Ln3+-mediated formation of luminescent ionogels

Abstract

A new organic salt consisting of aromatic carboxylic acid that can coordinate to and sensitize lanthanide ions such as Eu³⁺ and Tb³⁺ ions has been synthesized. Heating the mixture of organic salt and Eu³⁺ (or Tb³⁺) ions in MeOH, EtOH or DMF results in a homogenous solution. Luminescent ionogels are obtained by slowly evaporating the solvents. However, ionogels cannot be obtained when lanthanide ions are absent or if the aromatic carboxylic acid is deprotonated during the preparation of the ionogels. The amount of entrapped EtOH in the ionogels is 17% and 22%, respectively, for europium(III)-containing ionogels and Tb(III)-containing ionogels, respectively. The obtained ionogels exhibit intense emission lines upon UV light irradiation, owing to intramolecular energy transfer from the organic salt to lanthanide ions.