Reversibly Stretching Cocrystals by the Application of a Magnetic Field

Careful control of the noncovalent supramolecular interactions for the preparation of organic cocrystal materials with tailored properties is a challenging task. Herein, we report the reversible stretching of the distances between coformers (18-Crown-6/4,5-dicyanoimidazole (cocrystal 1) and (18-Crown-6/1,2,4-triazole (cocrystal 2) in the solution state, by the application of an external magnetic field with various strengths (0.0, 0.5, 1.0, and 1.5 T). As a consequence, the physical/chemical properties of the stretched cocrystals 1-0.5T, 1-1.0T, and 2-0.5T have been remarkably altered to close to the individual coformers, and finally, cocrystals 1 and 2 can be broken under 1.5 and 1.0 T, respectively. Thus, the stretching mechanism of a magnetic field can be proposed. This stretching effect, however, may therefore be of great interest in functional organic cocrystal materials that are tuned by noncovalent supramolecular interactions.