Tunable DynamicCoformer Enabling Diverse PhotoresponseBehaviors in Molecular Cocrystal Systems

Abstract

Abstract Recent progress in understanding the structure–photoresponse property relationship in molecular crystals has opened up many new opportunities in materials science. Although this structure–property correlation is well-known, utilizing a single target molecular system as a platform to unambiguously isolate the role of supramolecular structure in photoresponse performance, which is crucial in the development of engineering desired photoresponse behaviors, remains poorly explored. Herein, we report a hydrogen-bonding-regulated multiphotoresponse behavior based on a single target molecule, a pyridine-substituted cyanostilbene derivative (MPA), and a dynamic coformer acetic acid (HAc). Detailed analysis reveals that adjusting the proportion of HAc alters the hydrogen-bonding interactions between MPA and HAc, inducing a packing rearrangement of MPA and enabling a [2 + 2] cycloaddition reaction. This causes the originally photostable MPA crystals to transform into MPA-0.5HAc cocrystals and finally into the photoactive MPA-HAc cocrystals, thereby realizing a photoinduced twisting behavior. Furthermore, the hydrogen-bonding interactions in MPA-HAc cocrystals have been in situ regulated for a wide range of temperatures (from liquid-nitrogen temperature to 363 K); the rate of the [2 + 2] cycloaddition reaction and the deformation amplitude of the cocrystals can be affected, thereby facilitating a photoinduced cracking effect. Overall, the correlation among supramolecular packing, reaction kinetics, and macroscopic mechanical outputs is investigated, offering valuable insights into the rational design of responsive crystalline materials.