Macrocycle‐Conjugated Anthracenes Enable Thermochromic, Mechanochromic, and Supramolecular Polymorphic Properties in Organic Crystals

Abstract Macrocyclic arenes with robust architectures and captivating host‐guest properties are competitive supramolecular building blocks with highly adjustable intermolecular interactions and electron cloud distributions, enabling powerful control over intermolecular stacking modes to achieve supramolecular polymorphism. Herein, anthracene‐conjugated pillar[5]arene ( An‐P5 ) and leaning pillar[6]arene ( An‐LP6 ) are constructed as molecular models to investigate the regulation of thermochromic and mechanochromic behaviors stemming from the different aggregation patterns caused by different macrocyclic backbones. The flexible cavity of An‐LP6 promotes the formation of loosely packed H ‐aggregates, endowing its crystals with exceptional thermochromic and mechanochromic behaviors, which are distinct from the mixed stacking mode of An‐P5 and the herringbone‐shaped stacking of the planar anthracene analog without the macrocycle ( An‐Ph ). Moreover, host‐guest interactions between the macrocycles and appropriate guest molecules can further manipulate the aggregation states through synergistic effects of steric hindrance and electron cloud polarization, as validated by density functional theory (DFT) and X‐ray crystallographic analyses. In all, this work underscores how macrocycle‐mediated supramolecular polymorphism enables precise modulation of photophysical characteristics in organic crystals through structural confinement and guest tuning, paving new avenues for adaptive optoelectronic materials.