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The ability to make large changes in properties against small external stimuli is one of the key factors in sensing materials. Molecular domino transformation, i.e., polymorphic transformation starting at a stimulated point and extending to the whole crystal, is an attractive phenomenon from this viewpoint. We recently found such a transformation for the first time in an organic crystal of 4-nitro-N-salicylideneaniline as one of the Schiff bases. In this study, quantitative evaluations were conducted on the mechanical stimulus and emission properties in the transformation of the crystal. Our results demonstrate the potential applicability of the crystal to the detection of even less than a few μN mechanical stimuli as an emission color change. A molecular level transformation mechanism revealed by microcrystal electron diffraction also contributes to the future development of the transformation-based materials. [ABSTRACT FROM AUTHOR]

Described are two experimental findings: (1) selective CO2 uptake by dipeptide-based molecular crystals of Boc- L -methionyl- L -alanine methyl ester 1 with seemingly nonporous crystal architecture and (2) its CO2 sorption state successfully visualized at the atomic level by means of in situ X-ray crystallographic analysis. More important was the latter, from which intermolecular interactions between CO2 and the surrounding molecules of 1 in the crystal were analyzed by ab initio calculations, indicating that attraction between them was mainly composed of a dispersion force. In addition, a comparison study of the crystal structure of 1 with those of analogous dipeptide crystals (isomorphous with 1) demonstrated that the thermal fluctuations of the dipeptide molecules in the solid state triggered CO2 permeation into the isolated voids present in the crystal lattice of 1. [ABSTRACT FROM AUTHOR]

Some rodlike organic molecules exhibit exceptionally high layered crystallinity when composed of a link between π‐conjugated backbone (head) and alkyl chain (tail). These molecules are aligned side‐by‐side unidirectionally to form self‐organized polar monomolecular layers, providing promising 2D materials and devices. However, their interlayer stacking arrangements have never been tunable, preventing the unidirectional arrangements of molecules in whole crystals. Here, it is demonstrated that polar/antipolar interlayer stacking can be systematically controlled by the alkyl carbon number n, when the molecules are designed to involve effectively weakened head‐to‐head affinity. They exhibit remarkable odd–even effect in the interlayer stacking: alternating head‐to‐head and tail‐to‐tail (antipolar) arrangement in odd‐n crystals, and uniform head‐to‐tail (polar) arrangement in even‐n crystals. The films show excellent field‐effect transistor characteristics presenting unique polar/antipolar dependence and considerably improved subthreshold swing in the polar films. Additionally, the polar films present enhanced second‐order nonlinear optical response along normal to the film plane. These findings are key for creating polarity‐controlled optoelectronic materials and devices. [ABSTRACT FROM AUTHOR]

Solvate ionic liquids (SILs) composed of glymes and Li salts are potential electrolyte materials for Li ion batteries. Safety and durability of SIL‐based batteries can be realized by competing characters of solvate cations. Solvate structure of Li+ should be stable in the bulk to be nonvolatile, and its desolvation should occur rapidly on electrode surfaces which is considered as a rate‐limiting step in charging or discharging. To investigate such characters, potential‐dependent interfacial structure of [Li(G4)][TFSA], equimolar mixture of tetraglyme and lithium bis(trifluoromethanesulfonyl)amide, on an Au electrode has been investigated at the molecular scale by using surface‐enhanced infrared absorption spectroscopy. Despite discrete solvate ion [Li(G4)]+ is stable in the bulk, partial desolvation of Li+ on the electrode was observed at around the potential of zero charge, much more positive than Li+ reduction reactions. The driving force of the partial desolvation can be ascribed to the breaking of isotropic dielectric environment in the vicinity of the electrode, where image charge induced on the electrode surface stabilizes the partially desolvated structure enabling shorter Li+‐electrode distance. [ABSTRACT FROM AUTHOR]