Strategies to Diversification of the Mechanical Properties of Organic Crystals

• Published in: Angewandte Chemie Vol. 136; no. 24
• Main Authors: Dai, Shuting, Zhong, Jiangbin, Yang, Xiqiao, Chen, Chao, Zhou, Liping, Liu, Xinyu, Sun, Jingbo, Ye, Kaiqi, Zhang, Hongyu, Li, Liang, Naumov, Panče, Lu, Ran
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 10.06.2024
• Subjects: [2+2] cycloaddition; actuators; Crystals; Fluorination; Gliding; Halogenation; Mechanical properties; Modulus of elasticity; molecular crystals; Organic crystals; photochemical reactions; Photochemicals; photomechanical effect; Robust design; Shape memory
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.202320223

Structurally ordered soft materials that respond to complementary stimuli are susceptible to control over their spatial and temporal morphostructural configurations by intersectional or combined effects such as gating, feedback, shape‐memory, or programming. In the absence of general and robust design and prediction strategies for their mechanical properties, at present, combined chemical and crystal engineering approaches could provide useful guidelines to identify effectors that determine both the magnitude and time of their response. Here, we capitalize on the purported ability of soft intermolecular interactions to instigate mechanical compliance by using halogenation to elicit both mechanical and photochemical activity of organic crystals. Starting from (E)‐1,4‐diphenylbut‐2‐ene‐1,4‐dione, whose crystals are brittle and photoinert, we use double and quadruple halogenation to introduce halogen‐bonded planes that become interfaces for molecular gliding, rendering the material mechanically and photochemically plastic. Fluorination diversifies the mechanical effects further, and crystals of the tetrafluoro derivative are not only elastic but also motile, displaying the rare photosalient effect. This study demonstrates the effects of halogenation on the mechanical and photomechanical behavior of organic crystals. Starting with (E)‐1,4‐diphenylbut‐2‐ene‐1,4‐dione, the brittle photoinert crystals evolve into mechanically flexible, photochemically reactive crystals via double and quadruple halogenation, an approach that advocates for combined chemical and crystal engineering strategies to determine the key factors determining the solid‐state response dynamics.