Organic Molecular Crystal Exhibiting Superelastochromic Luminescence

Abstract

Despite lots of studies on mechanochromic luminescence to date, the number of reversibly controllable systems by varying the magnitude of stress are still limited. Here, we report so called "superelastochromism," a luminescence chromism of a crystal of an ESIPT compound based on superelasticity combined with the environmentally sensitive polymorph-dependent luminescence. Loading stress gradually onto a yellow-green luminescent crystal (7Cl-YG) of 7-chloro HPIP (7Cl) induced deformation with crystal-crystal phase transition, which resulted in formation of an orange-luminescent crystalline phase (7Cl-YO). The 7Cl-YO phase returned to the original 7Cl-YG phase spontaneously just by unloading stress. Superelastochromism provides real-time and continuous control of the ratio of biphasic emission colors by controlling the value of a single stimulus, namely the force stress.