Mechanical Motion in Crystals Triggered by Solid State Photochemical [2+2] Cycloaddition Reaction

Abstract

Some special crystals respond to light by jumping, scattering or bursting just like popping of popcorn kernels on a hot surface. This rare phenomenon is called the photosalient (PS) effect. Molecular level control over the arrangement of light-responsive molecules in microscopic crystals for macroscale deformation or mechanical motion offers the possibility of using light to control smart material structures across the length scales. Photochemical [2 + 2] cycloaddition has recently emerged as a promising route to obtain photo-switchable structures and a wide variety of frameworks, but such reaction in crystals leading to macroscopic mechanical motion is relatively less explored. Study of chemistry of such novel soft crystals for the generation of smart materials is an imperative task. This minireview highlights recent advances in solid-state [2 + 2] cycloaddition in crystals to induce macroscale mechanical motion and thereby transduction of light into kinetic energy.

Sunlight‐Induced In Situ Isomerization of Both Ligands in a Mixed‐Ligand Coordination Polymer: From Photosalient to Photoinert Crystals

“…Photoactuating molecular systems exhibiting conformational switching, movement, popping or some other mechanical effect may possess potential applications in remotely controlled devices, sensors, optical recording, defense field devices, storage devices and drug delivery process [4–7] . Ideally, such photoactuators would function without being any physical contact with the controlling system and reveal visually appealing mechanical effect i. e. photosalient effect [8–12] . These noncontact actuators have a prospect of converting light energy to mechanical energy.…”

“…[4][5][6][7] Ideally, such photoactuators would function without being any physical contact with the controlling system and reveal visually appealing mechanical effect i. e. photosalient effect. [8][9][10][11][12] These noncontact actuators have a prospect of converting light energy to mechanical energy. In view of present energy crisis situation and environmental issues, this process may have excellent donation towards future research on smart materials and laboratory to land applications.…”

“…There is a high possibility of photoinduced [2 + 2] cycloaddition reaction to show such phenomenon, where topochemical reaction occurs accompanied by reduction or increase in volume. 12 Thus, to investigate the plausible cause of the photosalient effect, we attempted to obtain single crystal of dimerized product. However, our several attempts have been failed due to fast reaction leading to disintegration of crystals.…”

Photoreactive Crystals Exhibiting [2 + 2] Photocycloaddition Reaction and Dynamic Effects

“…Photoreaction has traversed from simple structural transformations to the development of actuating materials, generating much research interest. 8,10 It is therefore necessary to understand the conceptual design principles for the development of stimuli responsive advanced materials. In this Account, we present some of our strategies and related investigations on solid-state structural transformation of olefinic compounds, summarize their applications, and point out the needs for future developments.…”

Photomechanical behavior triggered by [2 + 2] cycloaddition and photochromism of a pyridinium-functionalized coordination complex

“…S23, ESI †). At present, in the construction of photomechanical materials, 19 reducing structural complexity and enhancing non-covalent interaction forces have become a common strategy to ensure that the complex has the ductility to withstand deformation. In particular, the non-covalent bond interactions among these layers, serving as buffer layers, are weakened and probably even broken and re-formed in the bending process to relieve stress, whereby the overall crystal integrity is preserved.…”