Light-Induced Macroscopic Peeling of Single Crystal Driven by Photoisomeric Nano-Optical Switching

Single-crystal optical actuators are emerging as a prospective material form for nano-optical mechanical switching, sensing, or transduction device applications in nanotechnology and quantum technology. Crystal-lattice strain effects lie at the molecular origins of their macroscopic optical behavior, and linkage photoisomerization is an attractive source of optical actuation, if only suitably functioning materials of this ilk could be found. We discover η1-SO2 to η1-OSO single-crystal linkage photoisomerization in [Ru­(NH3)4(SO2)­(3-phenylpyridine)]­Cl2·H2O, which behaves macroscopically as a single-crystal optical actuator, whereby the crystal peels in response to light-induction at 100 K. It thermally recovers, whereupon the crystal exhibits remarkable restorative properties. We apply photocrystallography alongside concerted optical microscopy and optical absorption spectroscopy to reveal how the molecular origins of photoisomerization induce crystal-lattice strain that engenders this macroscopic crystal peeling effect. Linking structure and function across molecular and macroscopic length scales showcases a means by which single-crystal optically actuating materials could be systematically designed.