Photo‐ and Stress‐induced Bending of (E)‐1,2‐Bis(pyridinium‐4‐yl)ethene Dinitrate Crystals

We report on the elastic and photodynamic properties of (E)‐1,2‐bis(pyridinium‐4‐yl)ethene dinitrate [H₂Ebpe](NO₃)₂, whose needle‐like crystals can be reversibly deformed by applying external mechanical stress. The macro‐scale mechanical properties of [H₂Ebpe](NO₃)₂ crystals were quantified by a three‐point bending test, which gave a stress‐strain curve with an elastic modulus of 1.18 GPa, and its values are lower than those of other flexible elastic organic crystals. It can also be reversibly bent through the [2+2] cycloaddition reaction of the olefin moiety, depending on the direction of UV irradiation.