A tubular macrocycle from covalently linked anthracenes and meta-phenylene spacers

A novel tubular macrocycle containing four anthracene panels covalently linked by meta-phenylene spacers was synthesized. The tube is approximately 1 nm long with anthracene panels delimiting a columnar cavity with a diameter of ~1 nm and exhibits strong blue fluorescence.     

A Peanut‐Shaped Polyaromatic Capsule: Solvent‐Dependent Transformation and Electronic Properties of a Non‐Contacted Fullerene Dimer

Synthesis of molecular containers capable of incorporating multiple fullerenes remains challenging. Reported here is that room‐temperature mixing of metal ions with W‐shaped bispyridine ligands featuring polyaromatic panels results in the quantitative formation of a peanut‐shaped M₂L₄ capsule. The capsule reversibly converts into two molecules of an ML₂ double tube in response to changes in the solvent. Notably, the capsule allows the incorporation of two fullerene molecules into the connected two spherical cavities at room temperature. The close proximity yet non‐contact of the encapsulated C₆₀ molecules, with a separation of 6.4 Å, was revealed by X‐ray crystallographic analysis. The resultant, unusual fullerene dimer undergoes sequential reduction within the capsule to generate (C₆₀^.?)₂, C₆₀^.??C₆₀^2?, and (C₆₀^2?)₂ species. Furthermore, temperature‐controlled stepwise incorporation of two C₆₀ molecules into the capsule is demonstrated.     

A new nondestructive approach to chemical analysis of potsherds using an X‐ray fluorescence microscope: Case study about the past pottery manufacture in the Yaeyama Islands

In archeology, pottery represents an important class of artifacts giving information on the past human activity, the ecology, and ancient cultural groups. Some chemical analytic methods, including X‐ray fluorescent analysis, were adopted for the archeological study of pottery. However, these techniques also involve problems, including the destructive analysis of materials, and cannot analyze the original clay condition of pottery. To address this, we carried out nondestructive chemical analysis of 13 potsherds excavated from the Yaeyama Islands in the southern Japan archipelagos using X‐ray fluorescence microscopy. Two analytic methods were used, elemental mapping and multipoint spectral measurement, making it possible to obtain a visualized elemental distribution on potsherd surface and a detailed multipoint elemental composition of the same sample for the multivariate statistical analysis. In this study, the visualized images suggested that calcium particles were mixed to temper the materials, and their size and quantity differed between potsherds, whereas the uniformity of clay substrate, including the quantities of iron and silicon on multipoint measurement, was a characteristic of each potsherd. Therefore, principal component analysis and nonmetric multidimensional scaling analysis of the potsherds suggest that the differences between the Yaeyama Islands in terms of pottery manufacturing technology are due to chronological factors in this case. Our method represents an effective new approach to the pottery study for technological change.     

Tunable high-energy ion source via oblique laser pulse incident on a double-layer target

The laser-driven acceleration of high quality proton beams from a double-layer target, comprised of a high-Z ion layer and a thin disk of hydrogen, is investigated with three-dimensional particle-in-cell simulations for an obliquely incident laser pulse. The proton beam energy reaches its maximum at a certain incidence angle, where it can be much greater than the energy at normal incidence. The proton beam propagates at some angle with respect to the target surface normal and with some tilt around the target surface, as determined by the proton energy and the incidence angle.     

Microstructure of Highly Syndiotactic “Living” Poly(propylene)s Produced from a Titanium Complex with Chelating Fluorine‐Containing Phenoxyimine Ligands (an FI Catalyst)

Highly syndiotactic “living” poly(propylene)s were synthesized at 25°C using a bis[N‐(3‐tert‐butylsalicylidene)‐2,3,4,5,6‐pentafluoroanilinato]titanium (IV) dichloride/MAO catalyst system, and microstructures of the polymer were analyzed by means of ¹³C NMR spectroscopy. The syndiotactic poly(propylene) contains isobutyl, isopentyl and propyl end groups, suggesting that the living polymerization of propylene was initiated via 1,2‐insertion, followed by 2,1‐insertion as the principal mode of polymerization. Pentad distribution analysis revealed that the syndiospecific polymerization proceeds under chain‐end control.     

A Quantile General Index Derived from the Maximum Entropy Principle

We propose a linear separation method of multivariate quantitative data in such a way that the average of each variable in the positive group is larger than that of the negative group. Here, the coefficients of the separating hyperplane are restricted to be positive. Our method is derived from the maximum entropy principle. The composite score obtained as a result is called the quantile general index. The method is applied to the problem of determining the top 10 countries in the world based on the 17 scores of the Sustainable Development Goals (SDGs).     

Electronic effects on enantioselectivity in epoxidation catalyzed by D4-symmetric chiral porphyrins

Asymmetric epoxidation of various aromatic olefins was examined with our D₄-symmetric chiral porphyrin. The enantioselectivity was greatly improved upon when the substrates contained electron-deficient groups. Moreover, examination of electronic effects in the porphyrin catalyst revealed that electron-deficient groups lowered and electron-donating groups raised the enantioselectivity. Hammett plot analysis suggested that these electronic effects could be interpreted in terms of the Hammond postulate.     

Study on retention behavior of cyclic siloxanes by high resolution pyrolysis-gas chromatography with a fused silica capillary column

The general gas chromatographic retention behavior of cyclic methylsiloxanes partially substituted with phenyl or 2-cyanoethyl groups has been systematically studied, with pyrolysis-gas chromatography being utilized to form the cyclic siloxanes from the corresponding polysiloxanes at a temperature of 600°C. Kovats retention indices (KI) were determined for the cyclic siloxanes by use of the retention data of the pyrolyzates from polyethylene as standards. The effect of phenyl and 2-cyanoethyl substituents in the cyclic siloxanes on retention behavior has also been considered.