Phototriggered Guest Release from a Nonporous Organic Crystal: Remarkable Single-Crystal-to-Single-Crystal Transformation of a Binary Cocrystal Solvate to a Ternary Cocrystal

The
development of organic solids for applications in materials
science requires a fundamental understanding of how close packing
of molecules can affect structure and function. We report here nonporous
organic crystals that release entrapped guest molecules upon application
of UV light. We show components of binary cocrystal solvates to undergo
an intermolecular photoreaction to generate ternary cocrystals that
results in release of entrapped solvent molecules. The phototriggered
guest release occurs in a single-crystal-to-single-crystal transformation
that is in the absence pores and channels in the solid. The cocrystals
are composed of a tetratopic hydrogen-bond-acceptor molecule synthesized
in the solid state. The UV-light results in [2 + 2] photodimerization
of an isocoumarin to generate a ternary cocrystal with cyclobutane
molecules that support guest release.