Geminiarene‐Based Charge‐Transfer Cocrystals with Dichromatic Variants and Stimuli‐Responsive Structural Interconversion

The construction of stimuli-responsive charge-transfer (CT) cocrystals is a challenging frontier in organic crystal engineering. Here, we introduce a gemini CT cocrystal system with dichromatic stimuli-responsiveness by utilizing the unique dual/gemini conformational feature of geminiarene. Geminiarene binds with the electron-deficient guest 1,2,4,5-tetracyanobenzene through exo-wall interactions to form two types of gemini CT cocrystals with distinct colors. Single-crystal structures, along with theoretical calculations and spectral analyses, reveal that the color differences are primarily due to the dual molecular conformations of geminiarene and their distinct electronic properties. Notably, the gemini CT cocrystal system can be used to develop a novel dichromatic sensing material capable of distinguishing commonly used organic solvents. Moreover, the stimuli-responsive interconversion between the two conformations of geminiarene enables a loop-locked structural transition in the cocrystal system. This work expands CT cocrystal engineering and offers a new strategy for designing intelligent responsive materials for sensing and adsorption applications.