Piezochromic Luminescence of Cyano Substituted E/Z Isomeric Derivatives: Different Responses to External Stimuli

Abstract As an important class of stimuli‐responsive material, piezochromic organic materials have been widely investigated in recent years. To promote their further applications as pressure sensors, realizing a high sensitivity and big color contrast, especially under high external pressure, is of great importance. Herein, two pure cis/trans isomers, E‐ANTCN and Z‐ANTCN, based on anthracene and cyano substituted double bond are achieved. The molecular structures are determined by nuclear Overhauser effect spectroscopy, correlation spectroscopy, and X‐ray diffraction. At ambient conditions, both of them show typical mechanochromic characteristics under grinding−heating or grinding−fuming treatments. E‐ANTCN displays a sensitivity of 0.83 nm GPa −1 and a color contrast of 5 nm in a high‐pressure experiment, while Z‐ANTCN shows a much enhanced sensitivity of 22.64 nm GPa −1 and bigger color contrast of 110 nm, indicating the potential as a good colorimetric sensor for external pressure. The two cyano groups in the same side of double bond in Z‐ANTCN induce more intense intermolecular interactions with a resultant spatial packing mode being mainly responsive for its good sensing performance. This study fills the gap for a piezochromic property and high‐pressure experiment of E/Z isomers and provides useful information for the investigation of molecular structural changes under isotropic and anisotropic treatments.