Circularly polarised luminescence from excimer emission of anthracene derivatives complexed with γ-cyclodextrin in the solid state.

In this study, we report circularly polarised luminescence (CPL)-active molecules that exhibit high fluorescence quantum yields in the solid state. We developed anthracene derivatives with substituents at the 9 and 10 positions, such as ethyl(anthracene-9-carbonyl)glycinate (9AnGlyEt), N-butylanthracene-9-carboxamide (9AnB), N-benzylanthracene-9-carboxamide (9AnPh), and N 9,N 10-dibutylanthracene-9,10-dicarboxamide (9,10AnB). These compounds were complexed with γ-cyclodextrin (γ-CD) in the solid state by grinding, and the fluorescence properties of the resulting γ-CD complexes were investigated. The fluorescence quantum yields were enhanced after γ-CD complexation. Among the prepared γ-CD complexes, 9AnGlyEt/γ-CD had the highest fluorescence quantum yield (Φ f = 0.35), which was enhanced up to 5.8 times after γ-CD complexation. This was probably due to the interaction between the two anthracene molecules in the γ-CD cavity, which prevented fluorescence quenching caused by aggregation of the compounds. Positive CPL of g CPL = 1.3 × 10-3 was observed for 9AnGlyEt/γ-CD based on its excimer emission.

Charge-Segregated Stacking Structure with Anisotropic Electric Conductivity in NIR-Absorbing and Emitting Positively Charged π-Electronic Systems.

Squarylium-based π-electronic cation with an augmented dipole was synthesized by methylation of zwitterionic squarylium. The cation formed various ion pairs in combination with anions, and the ion pairs exhibited distinct photophysical properties in the dispersed state, ascribed to the formation of J- and H-aggregates. The ion pairs provided solid-state assemblies based on cation stacking. It is noteworthy that complete segregation of cations and anions was observed in a pseudo-polymorph of the ion pair with pentacyanocyclopentadienide as a π-electronic anion. In the crystalline state, the ion pairs exhibited photophysical properties and electric conductivity derived from cation stacking. In particular, the charge-segregated ion-pairing assembly induces an electric conductive pathway along the stacking axis. The charge-segregated mode and fascinating properties were derived from the reduced electrostatic repulsion between adjacent π-electronic cations via dipole-dipole interactions.