Size‐ and Orientation‐Selective Encapsulation of C70 by Cycloparaphenylenes

The size‐ and orientation‐selective formation of the shortest‐possible C₇₀ peapod in solution and in the solid state by using the shortest structural unit of an “armchair” carbon nanotube (CNT), cycloparaphenylene (CPP), has been studied. [10]CPP and [11]CPP exothermically formed 1:1 complexes with C₇₀, thereby giving the resulting peapods. A van′t Hoff plot analysis revealed that the formation of these complexes in 1,2‐dichlorobenzene was mainly driven by entropy, whereas the theoretical calculations suggested that the formation of the complex in the gas phase was predominantly driven by enthalpy. C₇₀ was found to exist in two distinct orientations inside the CPP cavity, namely “lying” and “standing”, depending on the specific size of the CPP. The theoretical calculations and the X‐ray crystallographic analysis revealed that the interactions between [10]CPP and the short axis of C₇₀ in its lying orientation were isotropic and similar to those observed between [10]CPP and C₆₀. However, the interactions between [11]CPP and C₇₀ in its standing orientation were anisotropic, thereby involving the radial deformation of [11]CPP into an ellipsoidal shape. This “induced fit” maximized the van der Waals interactions with the long axis of C₇₀. Theoretical calculations revealed that the deformation occurred readily with low energy loss, thus suggesting that CPPs are highly radially elastic molecules. These results also indicate that the same type of radial deformation should occur in CNT peapods that encapsulate anisotropic fullerenes.     

Hazard Evaluation Support System (HESS) for predicting repeated dose toxicity using toxicological categories

Repeated dose toxicity (RDT) is one of the most important hazard endpoints in the risk assessment of chemicals. However, due to the complexity of the endpoints associated with whole body assessment, it is difficult to build up a mechanistically transparent structure–activity model. The category approach, based on mechanism information, is considered to be an effective approach for data gap filling for RDT by read-across. Therefore, a library of toxicological categories was developed using experimental RDT data for 500 chemicals and mechanistic knowledge of the effects of these chemicals on different organs. As a result, 33 categories were defined for 14 types of toxicity, such as hepatotoxicity, hemolytic anemia, etc. This category library was then incorporated in the Hazard Evaluation Support System (HESS) integrated computational platform to provide mechanistically reasonable predictions of RDT values for untested chemicals. This article describes the establishment of a category library and the associated HESS functions used to facilitate the mechanistically reasonable grouping of chemicals and their subsequent read-across.     

Core Assembly Mechanism of Quinocarcin/SF-1739: Bimodular Complex Nonribosomal Peptide Synthetases for Sequential Mannich-type Reactions

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High-Energy Phosphonium Compounds and Their Application to Polymer Synthesis

High-energy phosphonium compounds, the N-phosphonium salts of pyridines, were prepared by the oxidation of phosphorous acid and its esters with mercuric salts or halogens in pyridines, or by a hydrolysis-dehydration reaction of diphenyl and triaryl phosphites or phosphonites. These salts are very reactive to nucleophiles, activating carboxyl, amino, or hydroxyl compounds via the corresponding N-phosphonium salts to yield carboxylic amides and esters in high yields on further aminolysis, alcoholysis, and acidolysis. These reactions, especially the hydrolysis-dehydration reactions with phosphites, were successfully extended to the direct polycondensation reaction of dicarboxylic acids with diamines, of free α-amino acids or dipeptides, and of carbon dioxide and disulfide with diamines under mild conditions, yielding linear polymers of high molecular weight (polyamides, polypeptides, polyureas, and polythioureas).     

Identification of the inclusion complexation between phenyl β-d-(13C6)glucopyranoside and α-cyclodextrin using 2D 1H or 13C DOSY spectrum

This study describes the 2D ¹H and ¹³C diffusion-ordered NMR spectroscopy (DOSY) experiments using the mixed sample of α-cyclodextrin (α-CyD) and phenyl β-d-(¹³C₆)glucopyranoside (1). Both the 2D ¹H and ¹³C DOSY spectra showed the component with a diffusion coefficient different from those of α-CyD and 1, which suggested the inclusion complexation of α-CyD with 1.     

Versatile Reactions of Organoboron Polymers Prepared by Hydroboration Polymerization

Hydroboration polymerization of dienes and thexylborane produces organoboron polymers, which can be regarded as a polymer homolog of trialkylboranes. In other words, the organoboron polymers obtained can be expected to be a novel type of reactive polymer. The present paper describes versatile reactions of organoboron polymers prepared by hydroboration polymerization. For example, reactions with carbon monoxide or with KCN were followed by oxidative treatment to produce the corresponding poly(alcohol)s or poly(ketone)s, respectively. The organoboron polymers were also reacted with bromopyridyl anion or with furyl anion to form cyano- or hydroxyl-containing polymers via ring-opening of pyridine or furan, respectively. Reductive treatment of the organoboron polymer gave the corresponding polymer after reductive cleavage of carbon—boron bonds.     

Self‐Organized Nanocomposite of Gold Nanoparticles and π‐Electron Organic Molecules

Aggregates of gold nanoparticles were formed by simple addition of a dithiafulvene derivative (DF) to an acetonitrile solution containing gold ions. The discrete gold nanoparticles in the aggregates were separated by monolayers of oxidized DF. No aggregation was observed with the addition of poly(vinylpyrrolidone) (PVP), which acted as a strong stabilizer and inhibited self‐assembly of the gold nanoparticles. DF acted as a reducing agent for gold ions, a stabilizer, and a tether for the resulting gold nanoparticles. Intermolecular S···S interaction and Au–S bonds might be the driving force for the self‐assembly of the gold nanoparticles.     

A one‐dimensional platinum mixed‐valence complex with bridging thiocyanate S atoms: [[PtII(en)2](μ‐SCN)[PtIV(en)2](μ‐SCN)](ClO4)4 (en is ethane‐1,2‐diamine)

A new one‐dimensional platinum mixed‐valence complex with nonhalogen bridging ligands, namely catena‐poly[[[bis(ethane‐1,2‐diamine‐κ²N,N′)platinum(II)]‐μ‐thiocyanato‐κ²S:S‐[bis(ethane‐1,2‐diamine‐κ²N,N′)platinum(IV)]‐μ‐thiocyanato‐κ²S:S] tetrakis(perchlorate)], {[Pt₂(SCN)₂(C₂H₈N₂)₄](ClO₄)₄}_n, has been isolated. The Pt^II and Pt^IV atoms are located on centres of inversion and are stacked alternately, linked by the S atoms of the thiocyanate ligands, forming an infinite one‐dimensional chain. The Pt^IV—S and Pt^II...S distances are 2.3933 (10) and 3.4705 (10) Å, respectively, and the Pt^IV—S...Pt^II angle is 171.97 (4)°. The introduction of nonhalogen atoms as bridging ligands in this complex extends the chemical modifications possible for controlling the amplitude of the charge‐density wave (CDW) state in one‐dimensional mixed‐valence complexes. The structure of a discrete Pt^IV thiocyanate compound, bis(ethane‐1,2‐diamine‐κ²N,N′)bis(thiocyanato‐κS)platinum(IV) bis(perchlorate) 1.5‐hydrate, [Pt(SCN)₂(C₄H₈N₂)₂](ClO₄)₂·1.5H₂O, has monoclinic (C2) symmetry. Two S‐bound thiocyanate ligands are located in trans positions, with an S—Pt—S angle of 177.56 (3)°.     

Use of whole‐body cryosectioning and desorption electrospray ionization mass spectrometry imaging to visualize alkaloid distribution in poison frogs

Ambient mass spectrometry is useful for analyzing compounds that would be affected by other chemical procedures. Poison frogs are known to sequester alkaloids from their diet, but the sequestration pathway is unknown. Here, we describe methods for whole‐body cryosectioning of frogs and use desorption electrospray ionization mass spectrometry imaging (DESI‐MSI) to map the orally administered alkaloid histrionicotoxin 235A in a whole‐body section of the poison frog Dendrobates tinctorius. Our results show that whole‐body cryosectioning coupled with histochemical staining and DESI‐MSI is an effective technique to visualize alkaloid distribution and help elucidate the mechanisms involved in alkaloid sequestration in poison frogs.     

Analysis of Nitrification in Agricultural Soil and Improvement of Nitrogen Circulation with Autotrophic Ammonia-Oxidizing Bacteria

Accumulations of inorganic nitrogen (NH₄ ⁺, NO₂ ^?, and NO₃ ^?) were analyzed to evaluate the nitrogen circulation activity in 76 agricultural soils. Accumulation of NH₄ ⁺ was observed, and the reaction of NH₄ ⁺?→?NO₂ ^? appeared to be slower than that of NO₂ ^??→?NO₃ ^? in agricultural soil. Two autotrophic and five heterotrophic ammonia-oxidizing bacteria (AOB) were isolated and identified from the soils, and the ammonia-oxidizing activities of the autotrophic AOB were 1.0?×?10³–1.0?×?10⁶ times higher than those of heterotrophic AOB. The relationship between AOB number, soil bacterial number, and ammonia-oxidizing activity was investigated with 30 agricultural soils. The ratio of autotrophic AOB number was 0.00032–0.26 % of the total soil bacterial number. The soil samples rich in autotrophic AOB (>1.0?×?10⁴ cells/g soil) had a high nitrogen circulation activity, and additionally, the nitrogen circulation in the agricultural soil was improved by controlling the autotrophic AOBs.