Chemical Storage of Ammonia through Dynamic Structural Transformation of a Hybrid Perovskite Compound.

Toward renewable energy for global leveling, compounds that can store ammonia (NH3), a carbon-free energy carrier of hydrogen, will be of great value. Here, we report an organic-inorganic halide perovskite compound that can chemically store NH3 through dynamic structural transformation. Upon NH3 uptake, a chemical structure change occurs from a one-dimensional columnar structure to a two-dimensional layered structure by addition reaction. NH3 uptake is estimated to be 10.2 mmol g-1 at 1 bar and 25 °C. In addition, NH3 extraction can be performed by a condensation reaction at 50 °C under vacuum. X-ray diffraction analysis reveals that reversible NH3 uptake/extraction originates from a cation/anion exchange reaction. This structural transformation shows the potential to integrate efficient uptake and extraction in a hybrid perovskite compound through chemical reaction. These findings will pave the way for further exploration of dynamic, reversible, and functionally useful compounds for chemical storage of NH3.

Supramolecular Architecture of an Amphiphilic Amino Alcohol as a Versatile Chiral Environment for Stereocontrolled Photoreaction of Various Anthracenes.

The photocyclodimerization of 2-anthracenecarboxylic acid has been extensively studied as a model reaction of asymmetric photochemistry. So far, numerous chiral environments have been employed to control this photoreaction, while the scope of photoreactants has been limited only to 2-anthracenecarboxylic acid and its simple esters and amides. Here, we developed a systematic series of photoreactants (2 a-d) by introducing various substituents to 2-anthracenecarboxylic acid, which showed different reactivities and selectivities depending on the substituents. By using the photoreactants 2 a-d, we evaluated the performance of a chiral environment composed of an amphiphilic amino alcohol (1), where the photocyclodimerization of 2 a-d generally proceeded in excellent regio- and enantioselectivities (71-98 % regio ratio, 76-86 % ee). Furthermore, by reacting 2 a and 2 b together in the chiral environment of 1, we succeeded in the first stereocontrolled cross-photocyclodimerization between two prochiral anthracenes (58 % chemo ratio, 83 % regio ratio, 90 % ee).

Functional Ionic Liquid Crystals.

Ionic liquid crystals have emerged as a new class of functional soft materials in the last two decades, and they exhibit synergistic characteristics of ionic liquids and liquid crystals such as macroscopic orientability, miscibility with various species, phase stability, nanostructural tunability, and polar nanochannel formation. Owing to these characteristics, the structures, properties, and functions of ionic liquid crystals have been a hot topic in materials chemistry, finding various applications including host frameworks for guest binding, separation membranes, ion-/proton-conducting membranes, reaction media, and optoelectronic materials. Although several excellent review articles of ionic liquid crystals have been published recently, they mainly focused on the fundamental aspects, structures, and specific properties of ionic liquid crystals, while these applications of ionic liquid crystals have not yet been discussed at one time. The aim of this feature article is to provide an overview of the applications of ionic liquid crystals in a comprehensive manner.

Helical supramolecular polymers with rationally designed binding sites for chiral guest recognition.

Since various helical supramolecular polymers became available, their application to molecular chirality recognition have been anticipated but not extensively studied. So far, only a few examples of chiral reactions have been reported, but none for chiral separation. Here, we report the application of a helical supramolecular polymer to the enantio-separation of chiral guest molecules. The monomer of this supramolecular polymer is the salt-pair of a dendritic carboxylic acid with an enantiopure amino alcohol. In an apolar solvent, this salt-pair stacks via hydrogen bonds to form a helical polymer. In conjunction with this carboxylic acid, various amino alcohols afford supramolecular polymers, whose helical handedness is determined by the stereochemistry of the amino alcohols. When two salts with the same chirality are mixed, they undergo copolymerization, while those with opposite chirality do not. Owing to this stereoselective copolymerizability, the helical supramolecular polymer could bias the enantiomeric composition of chiral amino alcohols.

Noncovalent Modification of Single-Walled Carbon Nanotubes Using Thermally Cleavable Polythiophenes for Solution-Processed Thermoelectric Films.

Four thermally cleavable polythiophene derivatives containing carbonate and solubilizing groups were synthesized for noncovalent modification of single-walled carbon nanotubes (SWCNTs). A well-dispersed polythiophene/SWCNTs composite was obtained by adsorption of the polymer at the SWCNT surface. The solution-processed composite film exhibited solid-state thermal cleavage of the insulating solubilizing group through decarboxylation, producing an insoluble composite film. The thermally cleavable composite film was evaluated for potential application as a thermoelectric (TE) material. The electrical conductivity (σ) of the thermally treated composite film was up to 250 times higher than that of the as-prepared composite film. The increased σ contributed to an increase in the power factor (PF). The ethanol-processed composite film could be applicable for green processing of a TE material using the less-toxic solvent. The substrate-free polythiophene/SWCNTs composite film prepared by simple solvent evaporation yielded a figure-of-merit of 3.1 × 10-2 with a PF of 28.8 µW m-1 K-2 at 25 °C. This solution-processed methodology is beneficial for the development of a flexible TE material.

Thiophene-Conjugated Ligand Probe for Nonenzymatic Turn-On Electrochemical Protein Detection.

A new type of turn-on electrochemical protein detection is developed using an electropolymerizable molecular probe. To detect trypsin, a benzamidine ligand is conjugated with a thiophene moiety. Encapsulation of the probe in the trypsin pocket prevents electropolymerization, leading to efficient electron transfer from the electrolyte to the electrode. In contrast, unbound probes can become electropolymerized, yielding a polythiophene layer on the electrode. The polythiophene formed this way suppressed electron transfer. The detection limit of trypsin using this electrochemical strategy is 50 nM. The method is shown to be useful for nonenzymatic turn-on electrochemical detection.

Shape-directed compartmentalized delivery of a nanoparticle-conjugated small-molecule activator of an epigenetic enzyme in the brain.

Targeted drug delivery to specific subcellular compartments of brain cells is challenging despite their importance in the treatment of several brain-related diseases. Herein, we report on shape-directed intracellular compartmentalization of nanoparticles in brain cells and their ability to deliver therapeutic molecules to specific organelles. Iron oxide (Fe3O4) nanoparticles with different morphologies (spheres, spindles, biconcaves, and nanotubes) were synthesized and coated with a fluorescent carbon layer derived from glucose (Fe3O4@C). In vivo studies showed that the Fe3O4@C nanoparticles with biconcave geometry localized predominantly in the nuclei of the brain cells, whereas those with nanotube geometry were contained mostly in the cytoplasm. Remarkably, a small-molecule activator of histone acetyltransferases delivered into the nuclei of the brain cells using nanoparticles with biconcave geometry showed enhancement in enzymatic activity by a factor of three and resulted in specific gene expression (transcription) compared with that of the molecule delivered to the cytoplasm using nanotube geometry.

Glucose- and pH-responsive charge-reversal surfaces.

We have shown a pH- and glucose-responsive charge reversal on silica surface through heterogeneous functionalization utilizing amines and boronic acid moieties. The dual responsiveness of the charge reversal has been unambiguously demonstrated through the desorption of charged chromophores. Interestingly, we observed a concentration-dependent desorption response to glucose at physiologically relevant levels.