Tomoki Ogoshi

Stereogenic carbon loses its stereochemistry when it is converted into planar carbocation. Retention of the chirality is difficult unless static reference chirality is introduced within reactant to change the reactions diastereoselective. Herein we report a rare reaction in which a stereogenic alcohol gives a chiral twisted tricyclic skeleton by acid-mediated dehydrative cyclization. The intermediates are carbocations without any stereogenic centers, and their non-stereogenic conformational features relay the chiral information to the product. The chiral twist is computed to be flexible in the alcohol reactant and initial carbocation intermediate, but it is induced through the reaction steps to acquire thermal robustness. This chirality relay also provides an effective synthetic method for each enantiomer of the product, which is a valuable intrinsically chiral building block.

Topochemical polymerization enables precise control over polymer structure by confining reactive sites within a preorganized crystal packing. However, accessing a different product generally requires redesign of the monomer. Here, we report a host–guest strategy that regulates the outcome of a photoinduced topochemical reaction without altering the monomer structure. We synthesized a macrocyclic pillar[5]arene monomer bearing polymerizable 1,3-diene groups. In the crystalline state, this monomer formed one-dimensional columns, and its packing mode was found to vary depending on the length of the encapsulated guest molecules. When 1,2-dichloroethane was encapsulated in the monomer cavity, its short length allowed the reactive 1,3-diene groups to align closely within the column. As a result, topochemical polymerization proceeded through a single-crystal-to-single-crystal transformation, affording a covalently linked one-dimensional polymer. By contrast, when the monomer cavity was occupied by the longer guest adiponitrile, the packing mode was altered, leading to preferential intercolumn dimerization. These results demonstrate that host–guest chemistry provides a distinct strategy for controlling the products of topochemical reactions.

Achieving high‐density single‐atom catalysts (SACs) remains a fundamental challenge, particularly for precious metals such as Ru that readily aggregate under synthetic and catalytic conditions. Here, we report a rational precursor design strategy for fabricating high‐density Ru SACs via direct carbonization, yielding ordered carbonaceous frameworks (Ru‐OCFs) with high Ru loadings of up to 11.0 wt%. By expanding the scope of precursors for OCF synthesis beyond conventional macrocyclic coordination motifs to coordinatively flexible polypyridyl ligands, we show that Ru‐terpyridine crystals with thermally polymerizable ethynyl units serve as effective precursors for immobilizing single‐atomic Ru species within three‐dimensional porous carbon frameworks, without metal aggregation or post‐synthetic treatments. The resulting Ru‐OCFs retain the ordered structure and coordination environment of the precursor crystals while simultaneously developing microporosity with high specific surface areas of up to 670 m ² g ⁻¹ . As a proof of concept, the high‐density isolated Ru sites in Ru‐OCFs enable enhanced catalytic activity in liquid‐phase CO ₂ hydrogenation, achieving a high formic acid productivity of up to 19 mmol g _cat ⁻¹ h ⁻¹ , outperforming representative nanoparticle catalysts.

Achieving high‐density single‐atom catalysts (SACs) remains a fundamental challenge, particularly for precious metals such as Ru that readily aggregate under synthetic and catalytic conditions. Here, we report a rational precursor design strategy for fabricating high‐density Ru SACs via direct carbonization, yielding ordered carbonaceous frameworks (Ru‐OCFs) with high Ru loadings of up to 11.0 wt%. By expanding the scope of precursors for OCF synthesis beyond conventional macrocyclic coordination motifs to coordinatively flexible polypyridyl ligands, we show that Ru‐terpyridine crystals with thermally polymerizable ethynyl units serve as effective precursors for immobilizing single‐atomic Ru species within three‐dimensional porous carbon frameworks, without metal aggregation or post‐synthetic treatments. The resulting Ru‐OCFs retain the ordered structure and coordination environment of the precursor crystals while simultaneously developing microporosity with high specific surface areas of up to 670 m ² g ⁻¹ . As a proof of concept, the high‐density isolated Ru sites in Ru‐OCFs enable enhanced catalytic activity in liquid‐phase CO ₂ hydrogenation, achieving a high formic acid productivity of up to 19 mmol g _cat ⁻¹ h ⁻¹ , outperforming representative nanoparticle catalysts.

Host–guest chemistry of an alkylated molecular liquid with a cyclic host realized a vapor-induced miscibility switching system, exhibiting macroscopic solid–liquid phase separation and turn-on room-temperature phosphorescence.

Carbonization of organic precursors is widely used to produce carbon materials. However, the morphology and properties of the resulting carbons remain difficult to predict and control owing to complex pyrolytic reactions. Here, by using pillar[5]arenes as a structurally defined macrocyclic platform, we show that their peripheral functionality regulates carbonization in three distinct pathways, early‐stage fixation, progressive coalescence, and melt‐assisted reconstruction, providing microporous frameworks and fused lamellar carbons. Modulating the precursor aggregation further tunes the morphology at the micrometer scale. These pathway‐defined architectures result in distinct functions, with microporous carbons favoring gas adsorption and lamellar carbons enabling electrical transport in exfoliated sheets. This work links the macrocyclic structure to the carbonization pathway and resulting properties, providing design guidance for converting molecular precursors into functional carbon materials.

Integration of dynamic helical polymers with supramolecular polymerization offers a promising strategy for constructing adaptive hierarchical chiral materials. However, the transformation of molecular‐level conformational changes in dynamic helical polymers into structural transformations at the supramolecular level remains unexplored. This study demonstrated the synthesis of supramolecular polymers composed of poly(phenylacetylene) (PPA) chains bearing a pillar[5]arene host unit at one chain end and complementary guest unit at the other. The telechelic PPAs were synthesized using a living polymerization method that enables precise end‐functionalization and subsequently assembled into supramolecular polymers through intermolecular host–guest interactions. To impart stimuli‐responsive behavior, alanine‐derived pendants, capable of forming intramolecular hydrogen bonds, were incorporated into the PPA chains. The resulting supramolecular polymers formed stable assemblies that persisted even after dilution below the concentration required for their initial formation. Solvent‐dependent switching of intramolecular hydrogen bonding induced simultaneous helicity inversion and modulation of the backbone rigidity, leading to pronounced morphological transformations of the supramolecular polymers between cyclic and rigid‐rod architectures, exhibiting viscosities up to 2000 times higher than the control polymer. These results demonstrate that molecular‐level conformational changes in dynamic helical polymers can be translated into higher‐order supramolecular structural transformations, providing a general strategy for designing adaptive hierarchical chiral materials.

Integration of dynamic helical polymers with supramolecular polymerization offers a promising strategy for constructing adaptive hierarchical chiral materials. However, the transformation of molecular‐level conformational changes in dynamic helical polymers into structural transformations at the supramolecular level remains unexplored. This study demonstrated the synthesis of supramolecular polymers composed of poly(phenylacetylene) (PPA) chains bearing a pillar[5]arene host unit at one chain end and complementary guest unit at the other. The telechelic PPAs were synthesized using a living polymerization method that enables precise end‐functionalization and subsequently assembled into supramolecular polymers through intermolecular host–guest interactions. To impart stimuli‐responsive behavior, alanine‐derived pendants, capable of forming intramolecular hydrogen bonds, were incorporated into the PPA chains. The resulting supramolecular polymers formed stable assemblies that persisted even after dilution below the concentration required for their initial formation. Solvent‐dependent switching of intramolecular hydrogen bonding induced simultaneous helicity inversion and modulation of the backbone rigidity, leading to pronounced morphological transformations of the supramolecular polymers between cyclic and rigid‐rod architectures, exhibiting viscosities up to 2000 times higher than the control polymer. These results demonstrate that molecular‐level conformational changes in dynamic helical polymers can be translated into higher‐order supramolecular structural transformations, providing a general strategy for designing adaptive hierarchical chiral materials.

Artificial water channels (AWCs) are synthetic systems biomimicking natural aquaporins (AQPs) that selectively transport water while rejecting ions. Amphiphilic rim-differentiated pillar[5]arenes and pillar[6]arenes, featuring cationic methylammonium and alkyl substituents on opposite rims, spontaneously assemble into two-dimensional channels with tunable pore sizes and channel lengths. Herein, we considered the alkyl chains (butyl-C4 and decatyl-C10) of these channels in relation to membrane partitioning and investigated the potential structure–activity relationships within the lipid bilayer. A synergistic effect of a large pore and favorable lipophilicity led to the highest water permeation (∼1 × 108 water molecules per channel per second) for AP-P6A-C10, as well as ion rejection. The present channels may be regarded as a rare biomimetic example of artificial channels that preferentially transport water while presenting low proton or ion transport activity.

A rapid method for quantifying the niacin metabolite 1-methylnicotinamide (1-MNA) in human blood is required to address the limitations of existing low-throughput techniques such as mass spectrometry. In previous studies, we demonstrated that supramolecular pillar[6]arenes (P6As) bearing either carboxylate groups (P6AC) or sulfonate groups (P6AS) functioned as "turn-off" fluorescent sensors for 1-MNA detection in urine by photoinduced electron transfer (PET). However, because the concentration of 1-MNA in blood is very low, PET-based detection in aqueous solutions was insufficient for reliable quantification on its own. Here, we report that phosphonate-functionalized P6A (P6AP) in 90% acetonitrile formed aggregates with columnar morphology, which was associated with markedly enhanced detection sensitivity for 1-MNA. Under these conditions, aggregation-induced emission (AIE) resulted in increases in the fluorescence intensity, photoluminescence quantum yield, and photoluminescence lifetime. The addition of 1-MNA suppressed the formation of columnar aggregates of P6AP, and this was accompanied by decreases in the fluorescence intensity, photoluminescence quantum yield, and photoluminescence lifetime. This solvation-dependent fluorescence response substantially improved the detection sensitivity for 1-MNA, enabling its detection in human blood. By contrast, in 80% acetonitrile, P6AP showed AIE but did not exhibit similar columnar aggregates or increase the sensitivity. Overall, the aggregation-state-associated enhancement of the fluorescence response provides a functional framework that enhances fluorescence-based detection and represents a promising platform for extension to a broad range of biologically relevant analytes.