More than Restriction of Twisted Intramolecular Charge Transfer: Three-Dimensional Expanded #-Shaped Cross-Molecular Packing for Emission Enhancement in Aggregates

This study developed a new solid-state, highly emissive phenylbenzoxazole-based organic compound, N-(4-(benzo[d]oxazol-2-yl)phenyl)-4-tert-butylbenzamide, which exhibited a distinct aggregation-induced enhanced emission. The solid fluorescence efficiency of the newly developed compound was 50.3%, whereas that in THF solution was only 0.22%. The single-crystal analyses revealed that a specific three-dimensional #-shaped cross stacking between molecules was observed in the solid/aggregated state, driven by specific C-H center dot center dot center dot pi interaction and various hydrogen bonds. The expansion of the cross-dipole stacking into the three-dimensional network was believed to be the dominant factor for the emission enhancement in the solids/aggregates, with respect to the assistant effect of the photoinduced twisted intramolecular charge transfer restriction.