Guest encapsulation and self-assembly of a cavitand-based coordination capsule

The synthesis and spectroscopic characterization of a cavitand-based coordination capsule 14 BF4 of nanometer dimensions is described. Encapsulation studies of large aromatic guests as well as aliphatic guests were performed by using 1H NMR spectroscopy in [D1]chloroform. In addition to the computational analysis of the shape and geometry of the capsule, an experimental approach to estimate the interior size of the cavity is discussed. The cavity provides a highly rigid binding space in which molecules with lengths of approximately 14 A can be selectively accommodated. The rigid cavity distinguished slight structural differences in the flexible alkyl-chain guests as well as the rigid aromatic guests. The detailed thermodynamic studies revealed that not only CH-pi interactions between the methyl groups on the guest termini and the aromatic cavity walls, but also desolvation of the inner cavity play a key role in the guest encapsulation. The cavity preferentially selected the hydrogen-bonded heterodimers of a mixture of two or three carboxylic acids 18-20. The chiral capsule encapsulated a chiral guest to show diastereoselection.     

Synthesis of photoreactive isopropyl-substituted poly(phenylene ether ether ketone)

Isopropyl substituted poly(phenylene ether ether ketone) with a high molecular weight was prepared by nucleophilic substitution reaction of isopropyl-substituted difluoro diaryl ether with hydroquinone. This polymer was amorphous and soluble in common organic solvents, such as THF, chloroform, and cyclohexanone. Thermogravimetry of the polymer showed good thermal stability, indicating that a 10% weight loss of the polymer was observed at 470°C in nitrogen. The glass transition temperature of the polymer was 145°C. The polymer had a broad UV absorption band over 250–380 nm. The polymer acted as a photosensitive resist of negative type for UV radiation. The resist had a sensitivity of 40 mJ/cm² and a contrast of 2.8, when it was developed with DMF at room temperature. © 1997 John Wiley & Sons, Inc.     

Conductive Nanoscopic Fibrous Assemblies Containing Helical Tetrathiafulvalene Stacks

Tetrathiafulvalenes (TTF) S‐TTF and R‐TTF having four chiral amide end groups self‐organize into helical nanofibers in the presence of 2,3,5,6‐tetrafluoro‐7,7′,8,8′‐tetracyano‐p‐quinodimethane (F₄TCNQ). The intermolecular hydrogen bonding among chiral amide end groups and the formation of charge‐transfer complexes results in a long one‐dimensional supramolecular stacking, and the chirality of the end groups affects the molecular orientation of TTF cores within the stacks. Electronic conductivity of a single helical nanoscopic fiber made of S‐TTF and F₄TCNQ is determined to be (7.0±3.0)×10^?4 S cm^?1 by point‐contact current‐imaging (PCI) AFM measurement. Nonwoven fabric composed of helical nanofibers shows a semiconducting temperature dependence with an activation energy of 0.18 eV.     

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).     

Estimated detection distance of a baiji's (Chinese river dolphin, Lipotes vexillifer) whistles using a passive acoustic survey method

Source levels and phonation intervals of whistles produced by a free-ranging baiji (Chinese river dolphin) were measured in the seminatural reserve of Shishou in Hubei, China. A total of 43 whistles were recorded over 12 recording sessions. The mean dominant frequency (the frequency at the highest energy) was 5.7 kHz (s.d. = 0.67). The calculated source level was 143.2 dB rms re 1 microPa (s.d. = 5.8). Most phonation intervals were shorter than 460 s, and the average interval was 205 s (s.d. = 254). Theoretical detection range of baiji's whistle was 6600 m at the present study site, but it could reduce a couple of hundred meters in practical noisy situation in the Yangtze River. Sporadic phonation (205 s interval on average) with relatively faint signal of baiji was considered to be difficult to be detected by a towing hydrophone system. Stationed monitoring or slow speed towing of hydrophones along the river current is recommended.     

Existence of homogeneous ideals fitting into long Bourbaki sequences

For any finitely generated torsion-free graded module over a polynomial ring, there exists a homogeneous ideal fitting into an exact sequence similar to a Bourbaki sequence even though its height is not restricted to two.

     

Molecular Transformation to Pyrroles,Pentafulvenes, and Pyrrolopyridines by [2+2] Cycloaddition of Propargylamines with Tetracyanoethylene

In this paper, we describe an efficient and atom-economical synthesis of highly functionalized pyrroles, pentafulvenes, and pyrrolopyridines by [2+2] cycloaddition–retroelectrocyclization of N-substituted propargylamines with tetracyanoethylene, followed by the treatment of the resulting tetracyanobutadiene derivatives with silica gel. In this reaction, silica gel plays an important role to promote the intramolecular cyclization to afford the heterocyclic products from the tetracyanobutadiene intermediates. The products were obtained selectively depending on the substituent on the nitrogen atom of the starting propargylamines.     

Aqueous synthesis of sialylglycopeptide-grafted glycopolymers with high affinity for the lectin and the influenza virus hemagglutinin

Glycopolymers with pendant complex-type sialyl N-glycans containing heptapeptides, that is, sialylglycopeptides (SGPs), were synthesized using a water soluble polymer backbone bearing N-hydroxysulfosuccinimidyl esters by post-polymerization modification in water. Although SGP has three amino groups on the peptide chain, the substitution reaction occurs preferentially at the N-terminus α-amino group in the lysine residue onto the polymer side chain because the reactivity of such α-amino group is higher than that of the ε-amino group in the lysine residue under mild acidic aqueous condition. The resulting SGP-grafted glycopolymers exhibited strong interaction with the lectin Sambucus sieboldiana agglutinin and the human influenza A virus hemagglutinin, with higher binding associate constant values than those of free saccharide according to quartz crystal microbalance analysis. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 548–556