Of eleven possible isomers for neutral S4, rectangular S4 has been proposed theoretically as one of the most stable forms. There has, however, been no consensus as to the S4 ground-state geometric structure despite much effort over recent years, because of the lack of direct structural information from experimental work due to lack of preparation in a pure state. The principal question is whether the ground-state geometry is rectangular D2h or open planar C2v. Our group found first rectangular S4 in coordination compounds of Rh and Ir tetranuclear complexes as a ligand and disclosed mysterious rectangular S4 by X-ray analysis and theoretical studies. Here, the newly developed chemistry of rectangular S4 complexes together with the related tetrasulfur species is introduced both from experimental and theoretical view points. In addition, more accurate argument of the principal question mentioned above is also described using results obtained from recent high-level theoretical calculations.
Mysterious rectangular S4 complexes as well as the related tetrasulfur species are disclosed both from experimental and theoretical view points.
A nickel-catalyzed heteroannulation has been developed where o-haloanilines react with alkynes to afford 2,3-disubstituted indoles. IPr (1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) was found to be an effective ligand for the reaction.
Super hard Ni–B/diamond composite coatings were prepared by electrodeposition. Such extreme hardness (ca. 2500 Hv) was ascribed to a large content of diamond particles and hardness of Ni–B matrix. Thermal treatment of the coatings resulted in the formation of Ni–B alloys, which led to increase in film hardness. This method is much simpler than previously reported methods for preparing hard coatings.
As a simulacrum of random copolymer poly(acrylamide-co-acrylic acid), partially hydrolyzed polyacrylamide (HPAM) self-assembled into polymeric micelles in pure aqueous solution in pH response. Spherical nanoparticles (D = 150 nm) were generated at pH 12, and giant semihexagonal nanoplates (450 nm × 250 nm × 50 nm) were obtained at pH 1.3, but no visible micelles were observed in pH 3–10. This is important for drug release considering the pH environment in human stomach and intestines. The giant semihexagonal micelles obtained at pH 1.3 are hierarchical multivesicular vesicles with the structure of (hydrophilic inner vesicle)@(hydrophobic continuous cyst wall)@(hydrophilic shell). These multivesicular vesicles were formed because the random copolymer has a random distribution of the hydrophilic units in the hydrophobic core. In addition, a new contrast enhancing strategy by in situ reduction gold doping that we established was efficient at illuminating the nanostructure of polymeric micelles with low contrast, and this strategy came with a way to obtain polymer nanoparticles smaller than 20 nm.
Highly polar ammonium ylide intermediates derived from α-halocarbonyl compounds were successfully trapped by cycloalkane phase-tagged activated alkenes via a cycloalkane-based thermomorphic (CBT) process, which allows for facile product isolation using a single liquid–liquid extraction step to effectively generate cyclopropane libraries in the cyclohexane phase.
Deformylflustrabromine, a marine indole alkaloid, was synthesized from 6-bromotryptamine, a plausible biosynthetic precursor, without protection of the amino group by a two-step reverse prenylation involving the Nicholas reaction and reductive decomplexation of the resulting acetylene dicobalt hexacarbonyl complex.
A novel easily available chemosensor 1 based on bis(N-salicylidene)ethylenediamine was reported, which exhibits highly selective and sensitive recognition toward Mn2+ in pure aqueous solution over a wide range of tested metal ions with a clear naked eye color change from colorless to red. This represents the first reported colorimetric chemosensor capable of detecting Mn2+ in aqueous solution.
Amorphous calcium phosphate nanoparticles were synthesized by mixing aqueous solutions of Ca(NO3)2 and (NH4)2HPO4. Then the particles were matured with sodium bis(2-ethylhexyl) sulfosuccinate (AOT) at various temperatures. Rod-shaped hydroxyapatite (HAp) nanoparticles were formed at maturation temperature ≥40 °C. These results indicate that addition of AOT not during the particles synthesis but during the maturation at more equal critical temperature is a key to form the rod-shaped HAp nanoparticles using AOT.
LiFe0.9V0.1(PO4)0.95F0.15/C was prepared via solid-state carbothermal reaction (CTR). F and V codoping did not alter the olivine structure of LiFePO4 but reduced the particle size and improved the Li+ diffusion coefficient. The cells based on this material showed higher discharge capacity, working voltage, rate capability, and better cyclic performance than that of undoped and F-doped materials.
A series of anthracene derivatives, 9,10-bis(bipyridyl, pyridylphenyl, phenylpyridyl, and biphenyl)anthracenes, were synthesized. They exhibited properties of small electron injection barrier from cathode in electron-only devices, high electron mobility from time-of-flight measurement, and high efficiency and stability of OLEDs.
We successfully synthesized Au–Pt bimetallic core–shell nanoparticles by simultaneous reduction covered with a perfluorinated sulfonic acid ionomer (PFSA) in an aqueous solution. The core–shell structure was confirmed by energy-dispersive X-ray spectrometry line analysis. Electrocatalytic activity of the Au–Pt nanoparticles for oxygen reduction reaction was higher than those of PFSA-covered Pt nanoparticles and a conventional carbon-supported Pt catalyst.
The dielectric constant (ε) of “water chains” incorporated in the channel of porous coordination polymer crystal [Cu(C6H4NO2)2] was small at low temperatures (ε ≈ 10) but became as large as 250 at 370 K. These dielectric behaviors were consistent with the results of molecular dynamics simulation and indicated that a melting of hydrogen-bonded water chains occurred above 300 K.
Pure perovskite-type LaTaON2 crystal powders with high crystallinity were synthesized in supercritical ammonia using sodium amide as a flux. The synthesis temperature for this new method is 873 K, approximately 300 K lower than that for previous methods. The obtained powders have a pseudocubic lattice with a lattice constant of a = 0.4049 nm, which is in good agreement with the reported value.
Asymmetric perfluoroamides with Li+ and Rb+ exhibited unusual phase transition behaviors such as very slow crystallization and a large shift in melting point of the melt-crystallized salts, which have not been reported in alkali metal salts so far. Considering that corresponding symmetric amides do not exhibit such unique phenomena, the structural asymmetry in anions serves an important role in these phase-transition behaviors.
We have prepared TiO2 nanotubes by anodization in HF or HF/H3PO4 mixed electrolyte. The morphologies and photocatalytic properties of the nanotubes were changed by electrolytes. The nanotubes prepared in HF/H3PO4 mixed electrolyte showed higher performance to decompose acetaldehyde by photocatalysis than those prepared in pure HF.
We demonstrated an efficient improvement of activity of Ni catalysts by combining with Mo and Mg elements, by which massive growth of multiwalled carbon nanotubes (MWNTs) with straight and double helical structures have been achieved from polypropylene (PP) by means of a one-step combustion method. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA) are applied to characterize the morphology and the purity of products.
Cyclic bis(3′–5′)diadenylic acid (c-di-AMP) (Chart 1), recently identified as a second messenger monitoring DNA integrity during sporulation in the soil bacterium Bacillus subtilis, was synthesized on an 80 µmol scale by a combination of the phosphoramidite and phosphotriester methods using a commercially available adenosine phosphoramidite as starting material. An artificial analog 2′-bis(tert-butyldimethylsilyl)-c-di-AMP was also obtained by our procedure.
Although alkyl sulfonates are commonly used for alkylating agents, there are very few reports on phase-transfer-catalyzed asymmetric alkylation with alkyl sulfonates. Herein, we report that the asymmetric reaction using glycine Schiff base 1 and optically pure epoxy triflates op-2 proceeded smoothly in the presence of phase-transfer catalyst (S,S)-4a to furnish γ,δ-epoxy-α-amino acids 3 in good yield with high enantioselectivity.
Uptake of Cs+ on poorly crystalline layered manganese oxide (Na birnessite) is reported. Distribution coefficients (Kd) showed significant uptake of Cs+ under acidic (pH 2.4) or basic conditions (pH 10.2). The uptake of Cs+ takes place with release of Na+ into the solution confirming ion exchange. The maximum uptake of Cs+ was 2.0 mmol g−1 at pH 10.2.
We have attempted to modify the surface of boron nitride (BN) nanoparticles by decylphosphonic acid and have characterized the surface layer of BN nanoparticles by means of high-resolution solid-state 31P NMR. The surface of BN nanoparticles was successfully modified, and the 31P NMR spectra showed two types of bonding states for the organic modifier. They are tentatively assigned to P–B and P–N bonding states from consideration of the residual line broadening due to interaction with quadrupole nuclei.
Exciplex-induced isomerization played a key role in highly efficient photoisomerization of stilbene-cored poly(benzyl ether) dendrimers tethering two alkoxycarbonyl surface functional groups at the meta position of each terminating phenyl group. This is the first report on the control of photochemical behavior of dendrimers using intramolecular exciplex formation.
An intermediate-frequency furnace was used for continuous production of hexagonal boron nitride (h-BN) by heating a mixture of C3N6H6 and H3BO3 in a flowing nitrogen gas at 1800–1950 °C. The products were examined by XRD, Raman, FTIR, and SEM. The results indicate the as-synthesized products are h-BN flakes with a purity of 98.73 wt %. A possible reaction mechanism is discussed.
Pd(II)-catalyzed formal O–H insertion reaction of diazonaphthoquinones to acetic acid proceeded to afford 1,2-naphthalenediol monoacetates. In the presence of lithium halides, halonaphthols were obtained under the reaction conditions.
Chemoselective polycondensation of 2-amino-4,6-dichloro-1,3,5-triazine (ADCT) was investigated with various aromatic diamines such as 4,4′-oxydianiline (ODA), 9,9-bis(4-aminophenyl)fluorene (BAFL), 4,4′-(hexafluoropropane-2,2-diyl)dianiline (BisAF), and bis(4-aminophenyl)sulfone (SODA) in the presence of potassium carbonate as a base. High-molecular weight perfectly linear polyguanamines (Mn ≈ 46000) were successfully obtained for the polycondensation of ADCT with BisAF, while the polycondensation of ADCT with BAFL afforded branched polyguanamines with a degree of branching of from 0.02 to 0.17.
The optical characteristics of polymer/metal composite films having metal nanoparticles periodically aligned in rows were explored. They were prepared by irradiating ultraviolet light on the polymer films containing metal complex spin-coated on a reflective surface. The films were found to exhibit band-selective mirror characteristics. The wavelength of maximum reflection can be controlled by changing the incident angle of the irradiating light.
A nickel-catalyzed cycloaddition of aromatic (O-benzyl)ketoximes with alkynes to afford 3,4-disubstituted isoquinoline derivatives has been developed. The reaction involves oxidative addition of N–O bond of O-benzylketoxime to Ni(0) and subsequent intermolecular C–H bond activation via elimination of benzyl alcohol. It was also found that ketoximes participate in the nickel-catalyzed reaction with alkynes to furnish isoquinoline N-oxide derivatives.
Cyclo(L-aspartyl-L-phenylalanyl)-containing poly(dimethylsiloxane) was synthesized through a simple procedure. This compound had a good organogelation or thickener ability in many organic solvents. X-ray diffraction showed that the gelator forms amorphous structure due to the presence of poly(dimethylsiloxane). Furthermore, some organogels were thixotropic in that reversible gel-to-sol transition was induced by mechanical stress.
The reaction of bis(dithiolene)sulfidotungsten(IV) complex with elemental sulfur yielded bis(dithiolene)(tetrasulfido)tungsten(IV) complex. A labeling experiment using 34S has indicated that the reaction is reversible and a sulfido(trisulfido)tungsten(VI) species is involved as an intermediate. The reaction represents a model reaction of polysulfide reductase of molybdoenzymes.
A simple and mild one-pot procedure for the synthesis of carbamoyl azides from acyl chlorides utilizing a combination of tetrachlorosilane and sodium azide in acetonitrile at ambient temperature is reported. Under gentle heating, 1-aryltetrazolin-5-ones were also obtained in one-pot process presumably via a [3 + 2] cycloaddition step.
A molecular valve, consisting of a poly(acrylic acid) gel-coated Au mesh and a Au mesh working electrode, allowed electrochemically control of a concentration where the valve opens. At open circuit and when +0.9 V vs. Ag/AgCl was applied to the Au mesh electrode, the valve opened at concentration higher than 3–4 × 10−4 M. At −0.7 V it increased to 9 × 10−4 M. On the other hand, it remained virtually constant for Ca2+ at those potentials.
The use of two-dimensional templates like clay, in the synthesis of graphitic carbon nitrides, make it feasible to form exfoliated layer like structures by polymerization of the precursors in the clay galleries. We have used clay linked with aminopropyl groups, aminoclay, to template the carbon nitride into mesolamellar structures. By virtue of its aminopropyl groups, aminoclay is further capable of reacting along with the intercalated precursors to enrich the carbon content of the resulting carbon nitrides.
Infrared spectra of protected amino acids, N-benzoxycarbonyl-L-proline and N-benzoxycarbonyl-L-isoleucine were measured in the gas phase from 10 to 3 µm. 4 and 3 conformers were found, respectively. The spectra in the 3 µm region reveal the carboxylic OH and amide NH bonds do not participate in hydrogen bonding with neighboring amide groups despite the highest acidity in the molecule. The spectra in the 10–5 µm region imply the main chain structure is the same among the conformers.
Improving the hydrogen permeation flux, while maintaining high hydrogen selectivity, is important for reducing membrane areas and enhancing membrane reactor (MR) performance. We have attempted to enhance the hydrogen permeation through the addition of nickel, which will improve both hydrogen adsorption and pore size control. The silica layer was deposited with high selectivity, using an extended counter-diffusion CVD method.
TiO2–WO3 composite fibers were prepared by electrospinning. The fibers have an average diameter of 1.0 µm. The XRD pattern of the TiO2–WO3 composite fibers indicates the presence of anatase and rutile phases of TiO2 and an orthorhombic phase of WO3. The photocatalytic degradation of acetaldehyde under visible light was achieved with the TiO2–WO3 composite fibers.
A new chelating diaryloxadiazole probe, oxazid displayed emission red shift and 16-fold emission enhancement upon binding with Zn2+ in buffered condition, while competing Cd2+, Ca2+, Mg2+, and several potentially quenching metal ions posed no significant optical interferences. Experimental evidences indicated 1:1 complexation, and the computational work revealed formation of a stable octahedral geometry.
Direct alkenylation of 1-phenylpyrazoles with alkenes such as acrylates accompanied by regioselective C–H bond cleavage proceeds efficiently under ruthenium catalysis in the presence of a copper oxidant. The procedure is also applicable to 2-phenylbenzothiazole and benzanilide.
A series of cyanamido-bridged di- and tetraruthenium complexes with η6-C6Me6 ligands have been synthesized, and their interconversion reactions have been investigated. Facile interconversion between the μ2-κN,κN and μ2-κN,κN′ coordination modes of NCNH ligands at a dimetallic core has been observed for the first time.
Highly anisotropic thin molecular films have been successfully prepared by depositing a bisazomethine dye under vacuum through evaporation on friction-transferred (FT) poly(tetrafluoroethylene) (PTFE) layers. The layers induce the high orientational degrees showing high dichroic ratios over 20 in their polarized UV–visible absorption spectra. Moreover, by modifying FT layers with the further PTFE evaporated and rubbing, the ratios are improved to remarkable values up to 44.
Crystalline hexagonal boron nitride (h-BN) hexagonal nanoplates were synthesized by the reaction of B2O3, NH4F, and metallic Na at 700 °C. The edge sizes of the hexagonal nanoplates are 400 nm, and the average thickness is 100 nm. As the reaction temperature was set at 500 °C, rhombohedral boron nitride (r-BN) triangular nanoplates nearly 200 nm across and about 20 nm thick were obtained. TGA analysis results reveal that thermal stability of h-BN hexagonal nanoplates was better than that of r-BN triangular nanoplates in air.
Trimethylsilyl triflate and tetrabutylammonium iodide (TBAI) effectively mediate the Prins cyclization of homoallylic alcohols and aldehydes to give 4-iodotetrahydropyrans with axial selectivity and good yields.
The effect of the protein environment on the short-lived compound I state of cytochrome P450cam was analyzed in detail by decomposing the ONIOM(B3LYP:AMBER) interaction energy between the active site and the surrounding protein environment into electrostatic, van der Waals (vdW), and polarization terms. The electrostatic effect was the largest in magnitude, followed by the vdW effect, and then by the polarization effect. The contributions of individual residues to the environmental effect were also evaluated.
We report the unidirectional transport of ionic dyes by new soft matter ratchets, which are made of melamine foam with non-centrosymmetric triangular shapes and driven by an AC electric field. The time evolution of the distributions of the ions in the ratchet has been analyzed to reveal that the ratchets can transport the ions preferentially in one direction with an asymmetric transport ratio of more than 7.
A novel mixed-valence Cu(I)–Cu(II) coordination polymer with an infinite one-dimensional (1-D) structure, [CuI4CuIII4(Mor-dtc)2(CH3CN)2]n (Mor-dtc−: morpholine dithiocarbamate), was prepared and structurally characterized by X-ray diffraction. This complex consists of a mononuclear copper(II) unit of [CuII(Mor-dtc)2] and a tetranuclear Cu(I) unit of [Cu4I4(CH3CN)2]. It also shows semiconductive behaviors with a relatively small activation energy, which was revealed by impedance analysis.
Diffusion coefficients (D) of arsenite and arsenate at various pH, or degrees of dissociation, were reported by diffusion cell, some values of which are newly reported in this letter. Systematic decrease of D depending on the dissociation of arsenite and arsenate shows that D is closely related to the size of the hydrated ions.
NHC-catalyzed generation of difluorocarbene from trimethylsilyl 2,2-difluoro-2-(fluorosulfonyl)acetate (TFDA) enables the synthesis of enol difluoromethyl ethers starting from cyclohexenones and tetralones. The resultant enol difluoromethyl ethers were successively dehydrogenated with DDQ to furnish aryl difluoromethyl ethers in good to high yield.