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 [H 2 Ebpe](NO 3 ) 2 , whose needle-like crystals can be reversibly deformed by applying external mechanical stress. The macro-scale mechanical properties of [H 2 Ebpe](NO 3 ) 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.