Photo-triggered phase transition of a crystal

Abstract

Structural phase transitions induced by external stimuli such as temperature, pressure, electromagnetic fields, and light play crucial roles in controlling the functions of solid-state materials. Here we report a new phase transition, referred to as the photo-triggered phase transition, of a photochromic chiral salicylideneamine crystal. The crystal, which exhibits a thermal single-crystal-to-single-crystal phase transition which is reversible upon heating and cooling, transforms to the identical phase upon light irradiation at temperatures lower than the thermal transition temperature. The photo-triggered phase transition originates from the strain of trans-keto molecules produced by enol-keto photoisomerization owing to the small energy barrier associated with changes in the crystal structure. The photo-triggered phase is metastable and returns to the initial stable phase via back isomerization from the trans-keto to enol form.

Photoinduced swing of a diarylethene thin broad sword shaped crystal: a study on the detailed mechanism

“…28 Also, such photoinduced phenomena accompanied by phase transition of a salicylideneaniline derivative were reported. 29 Aer the publication of our rst paper concerning the bending phenomena of diarylethene crystals, 30 we observed the swinging motions under constant irradiation with UV light on the single crystals of a diarylethene derivative 1oRR (Fig. 1a) with the thin broad sword shaped one prepared by sublimation.…”

“…(i) The photogenerated closed-ring isomer has a rigid sixmembered-ring in its molecular structure, 32 and its original unit cell is different from the open-ring isomer, and therefore the photogenerated closed-ring isomers themselves induce a strain to the surrounding unit cells of 1oRR, which works as a kind of pressure to induce the phase transition. 28,29 (ii) During the rst bending by expansion of the photo-irradiated side, the opposite side of the crystal suffers a compression to induce phase transition. However, the SCSC phase transition was also observed for rod-shaped crystals without bending.…”

Photomechanical Azobenzene Crystals

“…The mechanical function of the structural phase transition can be combined with the photomechanical response of photochromic crystals. Combining the structural phase transition with photoisomerization has resulted in multiple mechanical motions of crystals [51,52].…”

Conformational Polymorphism in Organic Crystals: Structural and Functional aspects - A Review

“…BIOVIA Material studio [34,42] is a computer simulation and modeling software that is useful for predicting potential polymorphs of a compound directly from its molecular structure. Users have a visual image to fully understand and compare polymorphic structures.…”

“…In response to external stimuli crystal structure rearranges in different forms exhibiting characteristics such as walking, bending, rolling, etc. This characteristic also allows molecular interaction to undergo reverse phase transition: the same locomotion on the opposite form or direction [5,42]. Size of crystals can also affect the movement: Thicker crystals exhibit slow bending and straightening while thinner crystals are able to exhibit these changes at a faster rate.…”