Strategies to Diversification of the Mechanical Properties of Organic Crystals

Abstract

Structurally ordered soft materials that respond to complementary stimuli are susceptible to control over their spatial and temporal morphostructural configurations via intersectional or combined effects such as gating, feedback, shape‐memory, or programming. In 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 also elastic but also motile, displaying the rare photosalient effect.

Crystal Engineering-Driven Sunlight Responsiveness and Flexible Waveguide Transmission

“…Driven by various mechanisms such as [2+2] cycloaddition, [4+4] cycloaddition, cis–trans isomerization, electrocyclization, and tautomerization, molecular crystals exhibit diverse properties, including bending, jumping, curling, fracturing, and twisting, − showcasing immense potential in fields like artificial muscles, micromechanics, light switches, actuators, and oscillators. − However, the currently reported light-driven actuators typically require artificial light sources [e.g., lasers, light-emitting diodes (LEDs), or xenon lamps] and manual control of the light direction to achieve crystal deformation, increasing the complexity of the driving system and limiting material miniaturization and intelligence. In contrast, the importance of sunlight, with its advantages of contactless operation, simple control, safety, and infinite resources, is undeniable.…”