Photoinduced Puffing with Large Volume Expansion and Photomechanical Motions induced by Topochemical [4+4] Reactions in Molecular Crystal Solvates

Abstract

AbstractIn this work, we report the first example of two crystal solvates of an anthracene‐benzhydrazide based molecule (Ant) that display very distinct photo‐responsive behaviour when 365 or 405 nm or visible light is illuminated. For the first time, the crystal hydrate that has water molecule in the lattice (hereafter named as Ant−H2O) display fascinating puffing behavior with large volume expansion upto 50 % accompanied with surface modulation when illuminated with 405 nm light, a phenomenon very much similar to the rice or popcorn puffing by thermal treatment. Utilizing the properties of photoconverted Ant−H2O crystals, we have demonstrated their application in photoinduced enhanced liquid absorption using various liquids/solutions. The other crystal solvate having DMF in the crystal lattice (hereafter named as Ant−DMF) responds to 405 nm light by bending, twisting, chopping, jumping or splitting etc. The chopping of Ant−DMF crystal was also observed under ambient/white light but at a slower rate compared to 405 nm light. Single crystal X‐ray diffraction study reveals that the photoinduced puffing and photomechanical effects of these materials are rooted to the topochemical [4+4] cycloaddition reaction between the anthracene moieties that facilitate molecular packing change assisted by the reconfiguration of intermolecular non‐covalent interactions involving lattice trapped solvent molecules.