Versatile responses beyond photomechanical behavior based on dynamic molecular crystals

Abstract

Photoresponsive dynamic molecular crystals, which can exhibit mechanical movements, have garnered growing interest due to their potential applications in photoactuators, switches, optical information storage, and soft robotics. The long-range, anisotropic molecular stacking structure, facilitated by weak intermolecular interactions in the crystal lattice, enables adaptive photomechanical responses to light, offering high-resolution wireless control at multiple scales. Recently, research interests have emerged in achieving multiple responsive behaviors accompanied by a photomechanical response, such as responses induced by a thermal effect, elastic deformation upon external stress, acidochromism, and fluorescence transformations. However, synergistically integrating different responsive properties within the same crystal system requires rational molecular design, modification of functional units, precise prediction of responsive properties, and consideration of molecular packing effects, which can lead to trade-offs. Moreover, delicate crystal engineering strategies are also necessary to balance intermolecular interactions and trigger multiple responses. This highlight paper focuses on recent progress in multiple-stimulus response in photomechanical molecular crystals, aiming to aid in the creation of new dynamic crystalline materials with more versatile responses.