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.

X-Seed 4: updates to a program for small-molecule supramolecular crystallography

X-Seed is a native Microsoft Windows program with three primary functions: (i) to serve as a graphical user interface to the SHELX suite of programs, (ii) to facilitate exploration of crystal packing and intermolecular interactions, and (iii) to generate high-quality molecular graphics artwork suitable for publication and presentation. Development of X-Seed Version 1.0 began in 1998, when point-and-click crystallographic software was still limited in scope and power. Considerable enhancements have been implemented within X-Seed over the past two decades. Of particular importance are support for the SHELX2019 programs (SHELXS, SHELXD, SHELXT and SHELXL) for structure solution and refinement, and MSRoll for rendering void spaces in crystal structures. The current version (i.e. Version 4) of X-Seed has a new interface designed to be more interactive and user friendly, and the software can be downloaded and used free of charge.

Covalent post-synthetic modification of switchable iron-based coordination polymers by volatile organic compounds: a versatile strategy for selective sensor development

A covalent post-synthetic modification is applied in one of the most relevant polymers to obtain unprecedented switchable spin crossover (SCO) materials. We also demonstrate that this material can be used as a selective chemo-sensor for VOCs (particularly, formaldehyde) thanks to solid/vapor reactions occurring between the polymer and the corresponding vapor.

Large negative linear compressibility of a porous molecular co-crystal

Flexible and transformable molecules, particularly those responding to external stimuli, are needed for designing sensors and porous compounds capable of storing or separating gases and liquids. Under normal conditions the photochromic compound, 1,2-bis[2-methyl-5-(pyridyl)-3thienyl]cyclopentene (BTCP) forms a porous co-crystal with 1,4-diiodotetrafluorobenzene (dItFB). It traps acetone (Ac) molecules in the pores. Owing to a unique system of pores in the polar framework, the crystal is sensitive to the humidity in the air and to the chosen liquid environment. When compressed in non-penetrating media, the crystal displays a strong negative linear compressibility (NLC) along [100].

Inclusion of a dithiadiazolyl radical in a seemingly non-porous solid

Incorporation of a dithiadiazolyl radical into a dynamic paramagnetic metallocycle yields an unusual paramagnetic hybrid material with exchange coupling between host and guest.