Light-fueled rapid macroscopic motion of a green fluorescent organic crystal

Abstract

We report here a new green fluorescent organic crystal of an amide functionalized acrylonitrile derivative (E-ArF₂) that displays various types of macroscopic response when illuminated with UV light (390 nm). The shape deformation and actuation of the E-ArF₂ crystal can be controlled on-demand by shining UV-light on the specific parts of the crystal and reversing the direction of light illumination. When UV light is shone on the (001) face of a straight crystal, it rapidly bends away from the light source and can be bent to the opposite direction by reversing the illumination direction on the other face (00−1). With the aid of various analytical techniques, NMR, IR, UV-vis and X-ray diffraction, we established that the light fueled macroscopic actuation of the E-ArF₂ crystal is rooted to the combined effect of E- to Z-isomerization and the [2 + 2] cycloaddition reaction in the solid state. Based on the above experimental facts, a general mechanistic model of the actuation is also proposed.