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.

A Zn(II) based one-dimensional (1D) coordination polymer (CP), [Zn(cis-1,4-chdc)(4-nvp)] (1) {cis-1,4-H2chdc = cis-1,4-cyclohexanedicarboxylic acid and 4-nvp = 4-(1-naphthylvinyl)pyridine} undergoes solid-state photochemical [2+2] cycloaddition reaction acompanied by mechanical motion, wherein crystals...

Single crystals of coordination complexes showing mechanical motion under the influence of external stimuli are of great interest due to their applications. Especially light-driven systems such as photoactuators, switches, and...

Six molecular salts of 2,6-naphthalene dicarboxylic acid (ndc-H2) and 4-carboxycinnamic acid (cca-H2) with 4-aminopyridine (4apy), 2-aminobenzimidazole (2abi) and 2-aminopyridine (2apy) have been synthesized. In the crystal structures of molecular salts...