Photomechanical Effects in Photochromic Crystals

Quantification of photoinduced bending of dynamic molecular crystals: from macroscopic strain to kinetic constants and activation energies

“…When some molecular crystals undergo physical or chemical transformation, they respond to the stresses and strains generated in their interior by bending, twisting, jumping, creeping, or other types of deformation or motion. 1 – 4 The research into these mechanical effects and the related solids, recently termed dynamic crystals, is rapidly evolving from the plethora of reports on serendipitous observations to an emerging research direction in materials science. The interest in these materials, however, extends beyond the mere academic curiosity and their visual appeal; there are now attempts to assess and even to gear the properties of dynamic crystals towards specific applications, such as in microactuators controlled by light, 5 heat or humidity, as macroscopic equivalents of the molecular machines within the realm of supramolecular actuation 6 – 22 and similar to the polymer actuators.…”

Determining the quantum yield of photochemical reactions in crystals from simultaneous effects of photothermal and photochemical bending of needle-shaped crystals

“…In the last decade, interest has grown in the study of dynamic crystal phenomena, which include various dynamic effects like bending, twisting, rapid displacements, and spontaneous destruction caused by phase or chemical transformations initiated by various stimuli such as heating or irradiation of crystals. [1][2][3][4][5][6][7][8] All such phenomena are associated with the occurrence of inhomogeneous strains due to inhomogeneous development of transformations in crystals. [9][10][11][12] Photomechanical effects, like bending of thin crystals caused by photoisomerization of the constituent molecules, are the most actively considered phenomena in this field as they can be used to create microactuators controlled by light.…”

Solid-State Structural Transformation in Zn(II) Metal–Organic Frameworks in a Single-Crystal-to-Single-Crystal Fashion

“…These structural changes in MOFs/CPs often generate strain in the framework and cause the loss of single crystallinity. In a few cases, this also leads to the violent mechanical motions of single crystals, especially those driven by photoreactions [ 23 , 35 , 36 , 37 ].…”