Macrocycle-Based Crystalline Sponge that Stabilizes and Lights Up Cationic Aggregation-Caused Quenching Dyes

Solid-state fluorescent materials play a critical role in the manufacture of light-emitting diodes, laser dyes, storage materials, and fluorescence sensors. However, it remains challenging to produce solid-state fluorescent materials using traditional organic dyes since most are subject to aggregation-caused quenching (ACQ) in the solid state. Here, a macrocycle-derived crystalline framework is reported that captures various cationic test-ACQ dyes (e.g., Basic Red 2 (BR2)) and stabilizes them in a fluorescent form. Cyclo[3](1,3-benzene)[3](4,6-benzene)(1,3-dicarboxylic acid), CA-3, is used as the core macrocyclic building block. When allowed to coordinate with Zn(NO3)(2)center dot 6H(2)O or Cd(NO3)(2)center dot 4H(2)O, crystalline sponge (CS-Zn or CS-Cd) is obtained. In the case of CS-Zn, nano-sized cavities are observed in the solid state that serve as containers to capture the cationic ACQ dye BR2 with loading yields up to 14.6 wt% and emission enhancements up to 41x of those seen for solid BR2. The resulting dye-containing material, CS-Zn@BR2, displays high stability in water or selected organic solvents at room temperature or under reflux, or when heated at 300 degrees C for 1 h open to the air, or in the presence of sodium hypochlorite solution (3.0 mm). This study highlights a new strategy for rendering fluorescent ACQ dyes in the solid state.

Automated summary

This study presents a new method for producing solid-state fluorescent materials by capturing and stabilizing cationic test-ACQ dyes using a macrocycle-derived crystalline framework. By coordinating CA-3 with metal ions to form a crystalline sponge, BR2 dye can be captured and stabilized, resulting in enhanced fluorescence intensity.