A Boryl‐Substituted Diphosphene: Synthesis,Structure, and Reaction with n‐Butyllithium To Form a Stabilized Adduct by pπ‐pπ Interaction

A boryl‐substituted diphosphene was synthesized through the nucleophilic borylation of PCl₃ with a borylzinc reagent, followed by a reduction with Mg. A combined analysis of the resulting diboryldiphosphene by single‐crystal X‐ray diffraction, DFT calculations, and UV/Vis spectroscopy revealed a σ‐electron‐donating effect for the boryl substituent that was slightly weaker than that of the 2,4,6‐tri‐tert‐butylphenyl (Mes*) ligand. The reaction of this diboryldiphosphene with ⁿBuLi afforded a boryl‐substituted phosphinophosphide that was, in comparison with the thermally unstable Mes*‐substituted diaryldiphosphene, stabilized by a π‐electron‐accepting effect of the boryl substituent.     

Formation, sintering, and electrical conductivity of perovskite Sm(Cr1−xMgx)O3 (0?x?0.23) prepared by the hydrazine method

The presence of SmCrO₄ is experimentally established. In Mg²⁺-substituted SmCrO₃, single-phase perovskite Sm(Cr_1−xMg_x)O₃, where x=0-0.23, are formed at ∼830°C by decomposition of Sm(Cr_1−xMg_x)O₄ which crystallizes at 530-570°C from amorphous materials prepared by the hydrazine method. Sm(Cr_1−xMg_x)O₃ solid solution powders consisting of submicrometer-size particles are sinterable; dense materials can be fabricated by sintering for 2 h at 1700°C in air. The relative densities, grain sizes, and electrical conductivities increase with increased Mg²⁺ content. Sm(Cr_0.77Mg_0.23)O₃ materials exhibit an excellent direct current electrical conductivity of 2.2×10³ S m⁻¹ at 1000°C.     

Polycyclic N-hetero compounds. XXXIII. Syntheses of 4-substituted 6,7-dihydro-5H-benzo[6,7]-cyclohepta[1,2-d]pyrimidines and their inhibitory activities on platelet aggregation and on reserpine-induced hypothermia

Various 4-substituted 6,7-dihydro-5H-benzo[6,7]cyclohepta[1,2-d]pyrimidines were synthesized by the reaction of 4-chloro-6,7-dihydro-5H-benzo[6,7]cyclohepta[1,2-d]pyrimidine with amines. Their inhibitory activities against collagen-induced platelet aggregation and also against reserpine-induced hypothermia in mice were investigated.     

Spontaneous copolymerization of 4-methylene-1,3-dioxolanes with maleic anhydride

The copolymerization of methylenedioxolanes, such as 4-methylene-1,3-dioxolane (I) and 2,2-dimethyl-4-methylene-1,3-dioxolane (II), with maleic anhydride (Manh) gives rise spontaneously to the alternating copolymers by the participation of charge-transfer (CT) complexes. The formation of CT complexes I-Manh and II-Manh was ascertained by UV and NMR spectroscopies. The equilibrium constants (K) could not be determined but were assumed to be small (K ? 1). For comparison with these systems an investigation of I-dimethyl maleate (DMM) and II-DMM systems was carried out to estimate K values 0.115 and 0.157 L/mol, respectively. To clarify the copolymerization mechanism I-Manh-acryronitrile was terpolymerized. Consequently it was concluded that the spontaneous copolymerization of I-Manh and II-Manh systems is effected by the CT complex monomer mechanism.     

Single-crystalline platinum nanosheets from nonionic surfactant 2-D self-assemblies at solid/aqueous solution interfaces

Single-crystalline platinum nanosheets have been prepared via a new methodology based on the chemical reduction of a platinum salt (H2PtCl6) with hydrazine at a graphite/solution interface, using polyoxyethylene (20) sorbitan monostearate (Tween 60) based self-assembly (hemicylindrical micelle) templates. The platinum nanosheets with a uniform thickness of as thin as 3.5 +/- 1 nm are surface-smooth and continuous over relatively large length scales of micrometer sizes. In striking contrast to the Tween 60 based system, no Pt nanosheets are obtained with nonaethylene glycol monododecyl ether (C12EO9) and polyoxyethylene (23) dodecyl ether (C12EO23). No Pt nanosheets are also obtainable with a laterally homogeneous layer of Tween 60 formed at the silica/solution interface. These results indicate that surfactant Tween 60 molecules with a triple polyoxyethylene structure, as well as their hemicylindrical micelle templates, play an essential role for the formation of the Pt nanosheets. It is also suggested that the interfacially directed growth of Pt metals within the aqueous shells of the Tween 60 hemicylindrical micelles induces the thin Pt crystals as thick as the aqueous shells. The present approach could be extended to prepare a wide range of novel nanostructures of noble metals, using various micelle-like self-assemblies at interfaces.     

Size of elementary clusters and process period in silver nanoparticle formation

The time dependence of small-angle X-ray scattering (SAXS) curves for silver nanoparticle formation was followed in situ at a time resolution of 0.18 ms, which is 3 orders of magnitude higher than that used in previous reports (ca. 100 ms). The starting materials were silver nitrate solutions that were reacted with reducing solutions containing trisodium citrate. The SAXS analyses showed that silver nanoparticles were formed in three distinct periods from a peak diameter of ca. 0.7 nm (corresponding to the size of a Ag(13) cluster) during the nucleation and the early growth period. The Ag(13) clusters are most likely elementary clusters that agglomerate to form silver nanoparticles.     

Novel methodology to control the adsorption structure of cationic porphyrins on the clay surface using the "size-matching rule"

Saponite-type clays that have different cation exchange capacities were successfully synthesized by hydrothermal synthesis. The structure and properties were analyzed by X-ray diffraction, X-ray fluorescence, (27)Al NMR, FT-IR, thermogravimetric and differential thermal analysis, atomic force microscopy, and cation exchange capacity measurement. The intercharge distances on the synthetic saponite (SS) surfaces were calculated to be 0.8-1.9 nm on the basis of a hexagonal array. The complex formation behavior between SS and cationic porphyrins was examined. It turns out that the average intermolecular distance between porphyrin molecules on the SS surface can be controlled, depending on the charge density of the SS. In the case of tetrakis(1-methylpyridinium-4-yl)porphyrin (H(2)TMPyP(4+)), the average intermolecular distances on the SS surface can be controlled from 2.3 to 3.0 nm on the basis of a hexagonal array. It was also found that absorption maxima of porphyrins depend on the charge density of the SS. The adsorption behavior of porphyrin on the SS surface can be rationally understood by the previously reported "size-matching rule". This methodology using host-guest interaction can realize a unique adsorption structure control of the porphyrin molecule on the SS surface, where the gap distance between guest porphyrin molecules is rather large. These findings will be highly valuable to construct photochemical reaction systems such as energy transfer in the complexes.     

A spectroscopic investigation of incompletely condensed polyhedral oligomeric silsesquioxanes (POSS-mono-ol, POSS-diol and POSS-triol): Hydrogen-bonded interaction and host-guest complex

¹H NMR dilution experiment and FTIR were used to investigate the hydrogen bonded interaction in three different types of incompletely condensed silsesquioxanes (POSS-mono-ol, POSS-diol and POSS-triol). For POSS-triol, there existed a dynamic equilibrium between single molecule and hydrogen-bonded dimer, and the dimerization constants (K_dim) of POSS-triol in different solvents were determined by ¹H NMR dilution experiment. In addition, based on hydroxy group which acted as hydrogen bond donors, the possibility of three POSS silanols as anion receptors to form host-guest complexes was also explored in this paper.     

One-pot synthesis of large FePt nanoparticles from metal salts and their thermal stability

One-pot synthesis of FePt nanoparticles larger than 5 nm with controlled composition has been developed by the polyol reduction of platinum acetylacetonate and iron acetylacetonate in excess ligands. The obtained large FePt nanoparticles (6.1 +/- 0.6 nm Fe36Pt64, 5.8 +/- 0.7 nm Fe44Pt56, and 5.1 +/- 0.7 nm Fe49Pt51 nanoparticles) were thermally more stable than the small ones and were hard to coalesce in the in-plane direction for their 2D superlattice.     

One-dimensional ion-conductive polymer films: alignment and fixation of ionic channels formed by self-organization of polymerizable columnar liquid crystals

We have prepared two types of one-dimensional ion-conductive polymer films containing ion nanochannels that are both perpendicular and parallel to the film surface. These films have been obtained by photopolymerization of aligned columnar liquid crystals of a fan-shaped imidazolium salt having acrylate groups at the periphery. In the columnar structure, the ionic part self-assembles into the inner part of the column. The column is oriented macroscopically in two directions by different methods: orientation perpendicular to the modified surfaces of glass and indium tin oxide with 3-(aminopropyl)triethoxysilane and orientation parallel to a glass surface by mechanical shearing. Ionic conductivities have been measured for the films with columnar orientation vertical and parallel to the surface. Anisotropic ionic conductivities are observed for the oriented films fixed by photopolymerization. The ionic conductivities parallel to the columnar axis are higher than those perpendicular to the columnar axis because the lipophilic part functions as an ion-insulating part. The film with the columns oriented vertically to the surface shows an anisotropy of ionic conductivities higher than that of the film with the columns aligned parallel to the surface.