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A well-oriented single-crystal membrane with high permeance is prepared by using a flexible single crystal of [[Cu.sub.2][(bza).sub.4](pyz)].sub.n] possessing one-dimensional (1D) penetration channels, where the membrane has displayed anisotropic gas permeation through the 1D channels with high permselectivity for [H.sub.2] and C[O.sub.2]. The studies have provided a new way of developing gas permeation membranes as sophisticated crystal devices for gas purification methods.

A novel molecular crystal membrane [Cu(ii)2(9-AC)4(pyz)]n (9-AC: 9-anthracenecarboxylate, pyz: pyrazine) shows high permselectivity for H2/CO (79.0), H2/CH4 (137), and H2/CO2 (12.1) due to the high rate of H2 permeation (3820 Barrer) while inhibiting the permeation of such a large gaseous particle even in its wider channel than the Lennard-Jones diameter of each gas. [ABSTRACT FROM AUTHOR]

Ferroelasticity has been reported for several types of molecular crystals, which show mechanical-stress-induced shape change under twinning and/or spontaneous formation of strain. Aiming to create materials that exhibit both ferroelasticity and light-emission characteristics, we discovered the first examples of ferroelastic luminescent organometallic crystals. Crystals of arylgold(I)(N-heterocyclic carbene)(NHC) complexes bend upon exposure to anisotropic mechanical stress. X-ray diffraction analyses and stress-strain measurements on these ferroelastic crystals confirmed typical ferroelastic behavior, mechanical twinning, and the spontaneous build-up of strain. A comparison with single-crystal structures of related gold-NHC complexes that do not show ferroelasticity shed light on the structural origins of the ferroelastic behavior., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Mechanical twinning changes atomic, molecular, and crystal orientations along with directions of the anisotropic properties of the crystalline materials while maintaining single crystallinity in each domain. However, such deformability has been less studied in brittle organic crystals despite their remarkable anisotropic functions. Herein we demonstrate a direction-dependent mechanical twinning that shows superelasticity in one direction and ferroelasticity in two other directions in a single crystal of 1,3-bis(4-methoxyphenyl)urea. The crystal can undergo stepwise twinning and ferroelastically forms various shapes with multiple domains oriented in different directions, thereby affording a crystal that shows superelasticity in multiple directions. This adaptability and shape recoverability in a ferroelastic and superelastic single crystal under ambient conditions are of great importance in future applications of organic crystals as mechanical materials, such as in soft robotics., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Ferroelasticity has been relatively well-studied in mechanically robust inorganic atomic solids but poorly investigated in organic crystals, which are typically inherently fragile. The absence of precise methods for the mechanical analysis of small crystals has, no doubt, impeded research on organic ferroelasticity. The first example of ferroelasticity in an organic molecular crystal of 5-chloro-2-nitroaniline is presented, with thorough characterization by macro- and microscopic methods. The observed cyclic stress-strain curve satisfies the requirements of ferroelasticity. Single-crystal X-ray structure analysis provides insight into lattice correspondence at the twining interface, which enables substantial crystal bending by a large molecular orientational shift. This deformation represents the highest maximum strain (115.9 %) among reported twinning materials, and the associated dissipated energy density of 216 kJ m -3 is relatively large, which suggests that this material is potentially useful as a mechanical damping agent., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Generally, superelastic behavior cannot be expected in mechanically twinned crystals because there is essentially no strain on the interface that is a driving force for spontaneous shape recovery. However, we found that single crystals of 3,5-difluorobenzoic acid are superelastic organic crystals under mechanical twinning. The unexpected shape recovery can be explained by molecular distortion on the twinning interface, which suggests a new mechanism for superelasticity in molecular materials., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)