title: Photoinduced Ratchet-Like Rotational Motion of Branched Molecular Crystals.
abstract: Photomechanical molecular crystals can undergo a variety of light-induced motions, including expansion, bending, twisting, and jumping. The use of more complex crystal shapes may provide ways to turn these motions into useful work. To generate such shapes, pH-driven reprecipitation has been used to grow branched microcrystals of the anthracene derivative 4-fluoroanthracenecarboxylic acid. When these microcrystals are illuminated with light of λ=405 nm, an intermolecular [4+4] photodimerization reaction drives twisting and bending of the individual branches. These deformations drive a rotation of the overall crystal that can be repeated over multiple exposures to light. The magnitude and direction of this rotation vary because of differences in the crystal shape, but a typical branched crystal undergoes a 50° net rotation after 25 consecutive irradiations for 1 s. The ability of these crystals to undergo ratchet-like rotation is attributed to their chiral shape.
authors.affiliation: Department of Chemistry, University of California, Riverside, 501 Big Springs Road, Riverside, CA, 92521, USA.
authors.forename: Lingyan
authors.initials: L
authors.lastname: Zhu
authors.affiliation: College of Science and Health Professions-3124, King Saud bin Abdulaziz University for Health Sciences.|King Abdullah International Medical Research Center, Ministry of National Guard Health Affairs, Riyadh, 11426, Kingdom of Saudi Arabia.
authors.forename: Rabih O
authors.initials: RO
authors.lastname: Al-Kaysi
authors.affiliation: Department of Chemistry, University of California, Riverside, 501 Big Springs Road, Riverside, CA, 92521, USA. christopher.bardeen@ucr.edu.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Bardeen
keywords: crystal engineering; crystal growth; energy conversion; materials science