Spiro-fused bicyclo[3,2,2] octatriene-cored triptycene: synthesis, molecular packing, and functional aggregates

Abstract

Aggregate science has led to the existence of functional properties at the aggregate level that significantly differs from those of corresponding single-molecule species, leading to a number of novel conceptual materials with state-dependent functionality. For developing such materials, new molecular scaffolds that allow modulating the structural and functional properties of aggregates in a controlled manner could be extremely helpful. In this study, we report a class of spiro-fused bicyclo[3,2,2] octatriene triptycene derivatives with a unique 3D molecular scaffolding structure that displays aggregation-induced emission (AIE) activity with bright solid-state blue luminescence. The core scaffold features a Y-shaped bicyclo[3,2,2]octatriene backbone and a vertical crossover arrangement of adjacent spiro-conjugated rings. Unlike classic bicyclo[2,2,2]octatrienes with high rigidity, this stereoscopic bicyclo[3,2,2]octatriene containing a seven-membered ring allows retaining certain flexibility in the molecular scaffold, which results in a weak fluorescence in dilute solutions (Φ F < 10%). However, the corresponding molecular aggregates emit intense fluorescence (Φ F = 50%-75%) and show prominent AIE activity because of the restriction of intramolecular scaffold motions. Moreover, in principle, these stereoscopic scaffold constructions with partially restricted flexibility facilitate the assembly of multiple different crystalline packing structures in both porous and nonporous forms depending on the growth conditions of crystalline aggregates. The obtained crystals with regular voids (12.85 × 6.89 Å each) show reversible luminescence in response to the adsorption/desorption of iodine vapor. These materials based on an unusual 3D scaffold exhibit a high degree of structural modulation at the aggregate level and demonstrate potential applications in chemical sensing and flexible optoelectronics, which may open up the exploration of highly stereoscopic molecular building blocks for developing functional aggregates.

Photoelectromagnetic Responsive Adaptive Porous Frameworks through Dynamic Covalent Chemistry of Tetraarylethylene‐backboned Aryldicyanomethyl Radicals

“…As shown in Figure 4, crystal 2 A displays continuous space voids with a complex tunnelling structure. The void volume value, as estimated by PLATON, [15] reached as high as 34.6 % for crystal 2 A and 35.4 % for crystal 2 B . It is clear that these non‐planar conformations of TPE building block contributed significantly to these unusual 3D tunnels.…”

A Photoelectromagnetic 3D Metal‐Organic Framework from Flexible Tetraarylethylene‐Backboned Ligand and Dynamic Copper‐Based Coordination Chemistry

“…If guest molecules are not considered, the total accessible void volume of HNU‐1 is estimated to be 59%, as calculated by the PLATON/SQUEEZE program (Figure 2G). [ 14 ] However, probably due to the unexpected structural collapse in the measurement, the activated HNU‐1 crystalline sample showed only a low Brunauer–Emmett–Teller surface area of 26.55 m 2 g −1 , and a maximum N 2 uptake value of 27.23 cm 3 g −1 N 2 isotherm at 77 K (Figure S3, Supporting Information). The corresponding CO 2 sorption at 1 atm was estimated to be 3.95 cm 3 g −1 at 273 K, and 1.92 cm 3 g −1 at 298 K (Figure S4, Supporting Information).…”

Aggregation-Induced Synthesis (AIS): Asymmetric Synthesis via Chiral Aggregates

“…Since THF and EtOH are typical cosolvents consisting of nonprotonic/less polar and protonic/more polar components for aggregation-induced emission (AIE) [18,37,38], we measured AIE of chiral Nphosphonyl imine (1a) in these solvents to support the formation of aggregates. After carefully adjusting the irradiation power (900 V) and wavelength (λex = 400 nm), as shown in Figure 3, this compound displayed an obvious AIE indicating an efficient formation of aggregates in THF/EtOH systems.…”