First aggregation-induced emission of a Tb(III) luminophore based on modulation of ligand–ligand charge transfer bands

Herein the aggregation-induced emission (AIE) of a Tb(III) complex is reported for the first time. The Tb(III) complex is composed of three anionic ligands (acac: acetylacetonate) and one large hetero-π-conjugated neutral ligand (dpq: dipyrido[3,2-f:2′,3′-h]quinoxaline). The formation of a crystalline J-aggregate of the Tb(III) complex (CJ-Tb(III)) was characterized by X-ray crystal structure analysis and absorption spectra. A crystalline H-aggregate (CH-Tb(III)) was also prepared using the ligand steric effect (tmh: 2,2,6,6-tetramethyl-3,5-heptanedionate). The emission and AIE properties of CJ-Tb(III) were evaluated using emission spectra, lifetime, and quantum yields, whereas CH-Tb(III) did not emit photons. Density functional theory calculations predict that the AIE originates from the modulation of ligand-to-ligand charge transfer bands through J-aggregation.