There is alimited number of reports on mechanically responsive molecular crystals,i ncluding thermo-responsive and light-responsive crystals.Rigid ordered molecular crystals with aclose-packing structure are less able to accept distortion, which hampers the development of such molecular crystals. The thermosalient effect, or "crystal jumping", refers to athermo-responsive system that converts heat into mechanical force by thermally induced phase transition. While they have recently attracted attention as potential highly efficient molecular actuators,less than two dozens of thermosalient molecular crystals have been reported to date,a nd the design of such molecules as well as how they assemble to express at hermosalient effect are unknown. Herein, we demonstrate how the cooperative molecular motion of twisted p units could serve to develop at hermo-responsive jumping molecular crystal with ah ydrogen-bonded organic framework (HOF) of tetra-[2,3]thienylene tetracarboxylic acid (1). The cooperative change in the molecular structure triggered by the desolvation of THF in the channel of the HOF structure induced not only ac hangei nt he structure of HOF but also mechanical force. Hydrogen bonding interactions contributed significant thermal stability to maintain the HOF assembly even with ad ynamic structural change.

There is alimited number of reports on mechanically responsive molecular crystals,i ncluding thermo-responsive and light-responsive crystals.Rigid ordered molecular crystals with aclose-packing structure are less able to accept distortion, which hampers the development of such molecular crystals. The thermosalient effect, or "crystal jumping", refers to athermo-responsive system that converts heat into mechanical force by thermally induced phase transition. While they have recently attracted attention as potential highly efficient molecular actuators,less than two dozens of thermosalient molecular crystals have been reported to date,a nd the design of such molecules as well as how they assemble to express at hermosalient effect are unknown. Herein, we demonstrate how the cooperative molecular motion of twisted p units could serve to develop at hermo-responsive jumping molecular crystal with ah ydrogen-bonded organic framework (HOF) of tetra-[2,3]thienylene tetracarboxylic acid (1). The cooperative change in the molecular structure triggered by the desolvation of THF in the channel of the HOF structure induced not only ac hangei nt he structure of HOF but also mechanical force. Hydrogen bonding interactions contributed significant thermal stability to maintain the HOF assembly even with ad ynamic structural change.

We demonstrated versatile hydrogen-bonded assemblies of a twisted π system with newly synthesized tetra­[3,4]­thienylene tetracarboxylic acid ThTCA. Due to its twisted saddle-shaped central π aromatic unit with an anisotropic arrangement of carboxyl units, a variety of dimensional solvate molecular crystals could be obtained, in contrast to typical aromatic carboxylic acid derivatives with low-dimensional assemblies. The versatile molecular assemblies could be converged to ThTCA desol by desolvation with a simple annealing technique. ThTCA desol showed selective solvent sorption behavior, which was governed by the solvent association energy and saturated vapor pressure. Especially, ThTCA desol showed the selective sorption of EtOH, among primary alcohols.

Crystal jumping behavior of a hydrogen‐bonded organic framework (HOF) is induced by collective molecular motion. In their Research Article on page 10345, T. Takeda et al. show a HOF composed of a twisted π framework of tetra[2,3]thienylene tetracarboxylic acid, which forms unique six‐fold interpenetrated diamondoid assemblies. Desolvation of the guest THF molecule in the channel of the HOF structure induces collective fluctuation of the twisted π framework, resulting in the crystal jumping behavior. The mechanism is schematically presented in the picture.

Molecular assemblies of twisted π molecules of tetraphenylene with long alkoxy chains (1) and tetra­[2,3]­thienylene with long alkylamide chains (2) or long alkoxy chains (3) and their dielectric properties were investigated. Different degrees of intermolecular interaction of 1–3 afforded different molecular assemblies, including an ordered columnar structure, disordered columnar, and lamellar structures. The introduction of long alkyl chains enabled us to create thermally stable liquid crystalline or liquid states. Temperature-dependent dielectric measurement revealed that the dynamic flipping motion of the tetra­[2,3]­thienylene core of 3 induced a temperature- and frequency-dependent dielectric anomaly in the neat liquid phase. This flipping motion of the central tetra­[2,3]­thienylene π core occurred relatively easily in the liquid state with a high degree of freedom of molecular motion.