Synthesis of a Cocrystal Hydrate by Sublimation and Reversible Polymorphic Transformation through Single-Crystal to Single-Crystal Fashion

Cocrystal hydrates are generally prepared by a solvent-mediated crystallization. Here we report for the first time the growth of crystals of a cocrystal hydrate by sublimation. Furthermore, the cocrystal hydrate exhibits polymorphism in which the polymorphs are interconvertible reversibly through a single-crystal to single-crystal fashion. During polymorphic transformation, the number of crystallographically nonequivalent molecules (Z″) increases in the asymmetric unit with decreasing temperature, which is an unusual phenomenon.