Capturing the Progressive Conformational Evolutions of Sterically-Congested Dihydrophenazines via Crystallization

Area of Science:

• Materials Science
• Organic Chemistry
• Crystallography

Background:

• N,N'-diphenyl-dihydrodibenzo[a,c]phenazine (DPAC) luminophores are known for their excited-state structural evolutions.
• Understanding these sequential multistep transformations is crucial for designing advanced materials.

Purpose of the Study:

• To investigate the conformational dynamics of DPAC derivatives.
• To explore the impact of cyano (CN) substitution on DPAC's crystalline behavior and structural diversity.
• To develop novel dynamic crystal materials.

Main Methods:

• Synthesis of cyano-substituted DPAC derivatives (DPAC-nCN, n=1-4).
• Single-crystal X-ray diffractometry to capture distinct molecular conformations.
• Crystallization techniques to induce conformational polymorphism.

Main Results:

• Cyano substitution facilitated access to diverse crystalline forms and conformational polymorphism in DPAC derivatives.
• DPAC-nCN derivatives showed increased conformational diversity with higher numbers of CN groups.
• DPAC-4CN exhibited multi-colored crystals (blue to red) with varying ring folding angles (~130° to ~172°).
• DPAC-4CN's planar red crystals demonstrated stimuli-responsive "jumping" behavior.

Conclusions:

• Cyano substitution is an effective strategy to control conformational evolution and induce polymorphism in DPAC systems.
• The study provides fundamental insights into the conformational dynamics of dihydrophenazines.
• DPAC-4CN represents a promising candidate for developing dynamic crystal materials with tunable optical properties.