Ordered array and motion of water molecules and ions at the interface between KBr(c)/NaCl(c) and water

The atomic-resolution images at the terrace of KBr(c)/NaCl(c) surface covered with water have been observed using an atomic-force microscope. The direct observation of the vertical motion of cations as well as the water-molecules ordered array at the interface was for the first time demonstrated in the atomic-resolution AFM image. The observed water molecules bridge each bromide ion-pair and are sandwiched between the potassium ions at the higher level right on the underlying bromide ions.     

Cyclodextrin-Based [c2]Daisy Chain Rotaxane Insulating Two Diarylacetylene Cores

A [c2]daisy chain rotaxane with two diarylacetylene cores was efficiently synthesized in 53 % yield by capping a C₂-symmetric pseudo[2]rotaxane composed of two diarylacetylene-substituted permethylated α-cyclodextrins (PM α-CDs) with aniline stoppers. The maximum absorption wavelength of the [c2]daisy chain rotaxane remained almost unchanged in various solvents, unlike that of the stoppered monomer, indicating that the two independent diarylacetylene cores were insulated from the external environment by the PM α-CDs. Furthermore, the [c2]daisy chain rotaxane exhibited fluorescence emission derived from both diarylacetylene monomers and the excimer, which implies that the [c2]daisy chain structure can undergo contraction and extension. This is the first demonstration of a system in which excimer formation between two π-conjugated molecules within an isolated space can be controlled by the unique motion of a [c2]daisy chain rotaxane.     

A Mixed-Anion System Consisting of a Germyl Anion and Anions Delocalized on Conjugated Carbon Ring Skeletons

A trianion consisting of one germyl anion and two anions delocalized on conjugated carbon ring skeletons was synthesized by trimerization of the germanium analogue of the anthryl anion, which exhibits high germylene character. In addition, the generation of the putative intermediate of this reaction, the radical anion of 9-germaanthracene, was confirmed by the formation of the corresponding dimeric dianion. The isolated trianion and dianion were characterized by X-ray crystallographic analysis together with NMR spectroscopy and theoretical calculations.     

Highly selective encaging of carbon dioxide molecules in the mixed carbon dioxide and nitrogen hydrate at low temperatures

The structural identification and guest compositions of the mixed CO(2) and N(2) hydrates at low temperature conditions were investigated by both theoretical predictions and experimental measurements. From the model calculations, at very low temperatures, the highly CO(2)-concentrated hydrates over 95 mol % CO(2) on the basis of water-free concentration could coexist with the gas mixtures of low CO(2) concentrations in equilibrium. X-ray diffraction measurements of the hydrates formed with the gas mixture of 3.16 mol % CO(2) and balanced N(2) indicate that the formed hydrates at all conditions considered in this study were identified as structure I, whereas the model predicts a structural transition to structure II around 220 K. However, it was also found that the formed hydrate samples contain a considerable amount of hexagonal ice resulting from incomplete conversion of ice to the hydrates. The compositional analysis suggests that a favorable encaging of CO(2) in the mixed hydrate can be obtained by the hydrate formation at low temperatures and relative amount of CO(2) molecules in the mixed hydrates increases with a decrease of temperature.     

Transmetalation in a Ce(III)‐phosphoester Crystalline Coordination Polymer with an Exceptionally High Selectivity for Yb(III) and Lu(III)

A novel crystalline coordination polymer containing Ce³⁺ and bis(4‐nitrophenyl) phosphate (L), CeL₃, was synthesized and its unique transmetalation selectivities toward Yb³⁺ and Lu³⁺ in the lanthanide series were evaluated. The relatively large difference in transmetalation selectivity between the neighboring Tm³⁺ and Yb³⁺ species is noteworthy because the reactivities of heavy lanthanides are generally considerably similar. The structural strain of the polymeric framework is likely responsible for this unusual trend. Powder X‐ray diffraction analysis indicated that, in the cases of only Yb³⁺ and Lu³⁺, large differences in their ionic sizes compared to that of Ce³⁺ in the parent framework may induce a structural strain after solid solution formation, while cleavage of the relatively weak Ce?O bond allows the formation of new Yb?O and Lu?O bonds with the incoming Yb³⁺ and Lu³⁺, respectively. Structural phase transitions likely caused by the heterogeneous nucleation of the Yb‐ (or Lu‐) type phase were also observed.     

Preparation, structure, and magnetic interaction of a Mn(hfac)2-bridged [2-(3-pyridyl)(nitronyl nitroxide)-Mn(hfac)2]2 chain complex

A new one-dimensional chain complex, Mn(hfac)(2)-bridged [2-(3-pyridyl)(nitronyl nitroxide)Mn(hfac)(2)](2), was prepared and its structure and magnetic properties were elucidated; the complex exhibited a large antiferromagnetic interaction of J(1)=-185 K between the three Mn(ii) atoms and the two nitronyl nitroxides to give S=13/2 spin units and a small ferromagnetic interaction of J(3)'=+0.02 K between these spin units at low temperatures (50-1.9 K), compatible with the theoretical analysis for model compounds.     

Mesoporous aluminosilicate-catalyzed Mukaiyama aldol reaction of aldehydes and acetals

A mesoporous aluminosilicate (Al-MCM-41) was found to be an effective heterogeneous catalyst for the reaction of both aldehydes and acetals with silyl enol ethers or ketene silyl acetals to give the corresponding aldol adducts in moderate to high yields. The remarkable high catalytic activity of Al-MCM-41 over amorphous silica-alumina and aluminum-free mesoporous silicate was observed in the reaction. The solid acid catalyst could be recovered easily by filtration and the recovered catalyst was reusable in the same reactions without a significant loss of catalytic activity.     

Self-disproportionation of enantiomers of non-racemic chiral amine derivatives through achiral chromatography

Efficient self-disproportionation of enantiomers of several non-racemic chiral amines was achieved through conversion to N-acetamides and subsequent MPLC using an achiral column. The MPLC of these non-racemic N-acetamide derivatives gave the chart having a clear boundary between two fractions. Thus, in the less polar fraction, remarkable enantiomer enrichment was observed (>99%ee), while the ee of more polar fraction was considerably reduced. The magnitude of the enantiomer enrichments and depletions strongly depended on substituent on the amino group.