Light-induced mechanical effects on crystals: from soft to catastrophic Tristan H. Borchers , Christopher J. Barrett, and Tomislav Friščić McGill University, Canada The past decade has seen an increased interest in photo-responsive and optical materials, namely materials which engage with light to produce desired, predictable responses. Polymers and liquid crystalline optical materials have been well-studied over the past 30 years, revealing materials that exhibit significant photo- mechanical effect, i.e., mechanical bending upon irradiation by visible or ultraviolet (UV) light. Our interest lies in the study and design of crystalline materials exhibiting photo-mechanical behavior and this presentation will outline the light-responsive behavior of organic single- and multi-component crystals (co-crystals) involving azobenzene dyes. Specifically, we will outline how the use of trans - and cis - isomers of a fluorinated azobenzene capable of acting as a halogen bond donor can lead to a wide diversity of new photo-responsive materials, exhibiting behavior that can be mild, such as changes in colour, or more profound, such as mechanical bending, 1,2,3 or even leading to crystal disintegration that can be used to enable micrometer-precision machining. 4 In particular, we will present a novel cocrystal material that can exhibit all three types of photo-responsive behavior depending on the density of applied visible laser radiation. References 1. Bushuyev, O. S., Tomberg, A., Friščić, T. & Barrett, C. J. Shaping Crystals with Light: Crystal-to-Crystal Isomerization and Photomechanical Effect in Fluorinated Azobenzenes. Journal of the American Chemical Society 135 , 12556-12559, doi:10.1021/ja4063019 (2013). 2. Bushuyev, O. S., Singleton, T. A. & Barrett, C. J. Fast, Reversible, and General Photomechanical Motion in Single Crystals of Various Azo Compounds Using Visible Light. Advanced Materials 25 , 1796-1800, doi:10.1002/adma.201204831 (2013). 3. Bushuyev, O. S., Corkery, T. C., Barrett, C. J. & Friščić, T. Photo-mechanical azobenzene cocrystals and in situ X-ray diffraction monitoring of their optically-induced crystal-to-crystal isomerisation. Chem. Sci. 5 , 3158-3164, doi:10.1039/ c4sc00987h (2014). 4. Borchers, T. H. et al. Cold photo-carving of halogen-bonded co-crystals of a dye and a volatile co-former using visible light. Nature Chemistry 14 , 574-581, doi:10.1038/s41557-022-00909-0 (2022).
P07
© The Author(s), 2022
Made with FlippingBook Learn more on our blog