Carbon-isotope chirality generated only by the substitution of carbon-13/carbon-12 can be amplified to enantioenriched 5-pyrimidyl alkanol by asymmetric autocatalysis, in which an extremely low enantiomeric excess (ca. 0.00005% ee) can automultiply during three consecutive reactions to >99.5% ee. Chiral carbon-isotopomers can act as a chiral trigger in the reaction between pyrimidine-5-carbaldehyde and diisopropylzinc to induce a small enantioselectivity in the resulting asymmetric autocatalyst, whose enantiomeric excess can be enhanced significantly by the subsequent asymmetric autocatalysis. Asymmetric autocatalysis has the enormous power to recognize the isotope chirality arising from the small difference between carbon (13C/12C) and hydrogen (D/H) isotopes. The tiny chiral influence in the hydrogen isotopically chiral amino acids such as glycine can be recognized and amplified by asymmetric autocatalysis. Furthermore, asymmetric autocatalysis can be applied to the highly sensitive chiral discrimination of cryptochiral compounds such as saturated quaternary hydrocarbon and isotactic polystyrene. Circularly polarized light, which is considered a possible candidate for the origin of chirality, acts as the chiral initiator in asymmetric autocatalysis, affording highly enantioenriched products with the absolute configuration correlated to the helicity of CPL. In addition, chiral crystals formed from achiral organic compounds can act as chiral initiators of asymmetric autocatalytic amplification of ee to afford enantioenriched (S)- and (R)-5-pyrimidyl alkanols corresponding to the solid-state chirality in chiral crystals.
Chiral carbon and hydrogen isotopomer, cryptochiral hydrocarbon, CPL, and chiral organic crystals can act as a chiral trigger of asymmetric autocatalysis with amplification of ee. Asymmetric autocatalysis of pyrimidyl alkanol has enormous power to recognize and amplify these small chiral influences.
Organic/inorganic nanohybrid materials composed of terthiophenes and imogolite were prepared by means of specific surface interaction between a phosphonic acid group in terthiophene derivatives and aluminol groups on the surface of imogolite. The new materials were investigated by FTIR, UV–vis absorption, fluorescence spectroscopy, TEM observation, nitrogen adsorption–desorption, and I–V measurement. Addition of terthiophene of phosphonic acid derivatives into imogolite brought some changes in absorption and photoluminescence spectra, suggesting the formation of H-type aggregate on imogolite surface. The analysis of UV–vis spectra and nitrogen adsorption–desorption data provided insight into the effect of molecular structure of terthiophenes on the adsorption and aggregation behaviors on the imogolite surface. In addition, a significant enhanced current flow was observed through imogolite film when imogolite was chemisorbed by electron-withdrawing terthiophenes. In contrast, current flow decreased as the electron-donating terthiophene was chemisorbed on imogolite. A possible mechanism for such phenomena is discussed.
Organic/inorganic nanohybrid materials composed of terthiophenes and imogolite were prepared by means of specific surface interaction between a phosphonic acid group in terthiophene derivative and aluminol groups on the surface of imogolite.
We have investigated the cation-exchange behavior of element 104, rutherfordium (Rf), together with its lighter group-4 homologs Zr and Hf, and the tetravalent pseudo-homolog Th in HF/HNO3 mixed solution. The results, obtained on a one-atom-at-a-time scale, demonstrate that distribution coefficients (Kd) of Rf in HF/0.10 M HNO3 decrease with increasing concentration of the fluoride ion [F−]. This resembles the behavior of the homologs, indicating the consecutive formation of fluorido complexes of Rf. We also measured the Kd values of Rf and the homologs as a function of the hydrogen ion concentration [H+] in the range of [F−] = 5.29 × 10−7–3.17 × 10−6 M. The log Kd values decrease linearly with an increase of log[H+] with slopes between −2.1 and −2.5. This indicates that these elements are likely to form the same chemical compounds: mixture of [MF]3+ and [MF2]2+ (M = Rf, Zr, Hf, and Th) in the studied solution. It is also ascertained that the fluorido complex formation of Rf is significantly weaker than that of Zr and Hf, but it is stronger than that of Th.
N-p-Vinylbenzyl-6-D-glucaramic acid (VB-6-D-GlcaH, 1) and its corresponding polymer, P(VB-6-D-GlcaH-co-AAm) (2), were found to inhibit β-glucuronidase activity more efficiently than D-glucaro-6,3-lactone, while the inhibition ability of N-butyl-6-D-glucaramic acid (Butyl-6-D-GlcaH, 3) on the enzyme activity was seriously lower than that of the lactone. The π–π stacking interaction between the styryl part of 1 and Trp587 of β-glucuronidase was confirmed by the blue shift detected on fluorescence spectrophotometry and the observation of the 3D motif for the active site with the glycomonomer, which must enhance the inhibition ability of the enzyme. In the case of 2, however, such a shift was not observed, which indicated that the effective inhibition of 2 was induced not by the π–π stacking interaction but a polymeric effect. Based on these results and our previous work, plausible conformations of 1 and 2 fitting in β-glucuronidase were proposed.
The complexation behavior of cyclodextrins (CDs) with a dumbbell molecule possessing ferrocene (Fc) moieties at both the ends (FcC10Fc) was investigated by 1H NMR, two-dimensional rotating frame Overhauser spectroscopy, circular dichroism spectroscopy, and cyclic voltammetry. α-CD includes the cyclopentadienyl rings of the Fc moiety shallowly from the wider side but not the decamethylene (C10) moiety, whereas β-CD and γ-CD include not only the Fc moiety but also the C10 moiety. These observations indicate that the Fc moiety can pass through β-CD and γ-CD cavities but not the α-CD cavity.
A series of perovskite halide solid solutions was synthesized and characterized by DTA and X-ray diffraction. The solid solution CH3NH3SnBr3−xClx (x = 0–3) changes its color from red, orange, yellow to a colorless state with increasing x. Although each highest temperature phase belongs to a cubic system, a slight trigonal distortion was observed above x = 1.0 at room temperature. Similar continuous solid solutions with black colors were confirmed for CH3NH3SnBr3−xIx (x = 0, 1, 2, and 3) keeping a cubic perovskite structure over the whole x region. On the other hand, continuous solid solutions CH3NH3SnI3−xClx could not be confirmed. The solid-state static 1H NMR suggested that the isotropic reorientation of the cation does not freeze even at 150 K for the perovskite having a large anionic sublattice. The characteristic changes of the color and the electric structure for these perovskites were discussed analytically on the basis of the tight-binding approach. This simple one-dimensional expression predicts that the tin(II) perovskite halide is a direct band gap semiconductor with tailorable properties.
Reaction profiles for catalytic urethanation are analyzed by DFT calculations. A well-known basic catalyst 1,4-diazabicyclo[2.2.2]octane (DABCO) activates alcohol molecules and accelerates the direct addition toward isocyanates. Self-catalysis by alcohols is also characterized as an accelerated direct addition.
A 2D iron(II) spin-crossover (SCO) complex, [FeII(HLH,Me)2](CF3SO3)2, was synthesized, where HLH,Me: 8-(imidazol-4-ylmethylideneamino)-2-methylquinoline, and its structures and magnetic properties were investigated. The complex [FeII(HLH,Me)2](CF3SO3)2 has no crystal solvent and has structure isomorphous to the complex [FeII(HLH,Me)2](ClO4)2·1.5MeCN, and shows a gradual and reversible one-step SCO between the HS (S = 2) and LS (S = 0) states at T1/2 = 215 K without hysteresis. The T1/2 value is higher than that of corresponding desolvated ClO4− compound, [FeII(HLH,Me)2](ClO4)2, about 35 K, although the spin transition is more gradual than that of ClO4− compound and the hysteresis is absent, which is observed in ClO4− compound. The crystal structures were determined at 296 (HS state) and 100 K (LS state), where the crystal system and space group showed no change between these temperatures. The structures at both temperatures have the same 2D layered structure, which is constructed of both the bifurcated NH···O− hydrogen bonds between two CF3SO3− ions and two neighboring imidazole NH groups of the [FeII(HLH,Me)2]2+ cations and the π–π interactions between the two quinolyl rings of the two adjacent cations. This network structure is the same as that of ClO4− compound. 600 nm light irradiation at 10 K induced the LIESST effect.
Four new pregnane steroids, ceratosteroid A (1), B (2), C (3), and D (4), were isolated from the Formosan red alga Ceratodictyon spongiosum and symbiotic sponge Sigmadocia symbiotica. The structures were elucidated by 1D and 2D NMR spectral analyses. Compounds 2 and 4 showed cytotoxicity against P-388 cell line.
The preparation of gold nanoparticles using silver-salt photographic materials and a method of gold-deposition development are investigated. Although gold rapidly precipitated in the gold-deposition developer when ascorbic acid was added, gold atoms were deposited only on the exposed areas of the photographic plate when the plate was immersed in the solution. While the deposition proceeds slowly via the disproportionation reaction of gold(I) ions in the absence of ascorbic acid, the addition of ascorbic acid accelerates the deposition rate significantly and increases the photosensitivity of the photographic plate. The gold deposition is catalyzed by photolytic silver specks, called latent image specks, on silver halide grains. Absorption spectra and TEM observations suggest a broadening of the particle size distribution, and this indicates that the difference in the catalytic activities of the photolytic silver specks between the two reactions is due to the difference in the critical size of the silver specks for triggering the deposition. Because the catalysts were prepared using light, light-based control of the catalytic properties may be possible.
An eco-friendly and efficient procedure for synthesis of 2-methylquinoline derivatives from nitroarenes has been developed by a simple one-pot reaction on the surface of platinum-loaded TiO2 with neat ethanol under UV irradiation without any harsh reagent according to green chemistry. TiO2 catalysts with various amounts of Pt loadings were prepared by photodeposition using chloroplatinic acid solution and characterized by XRD, BET, AFM, HR-TEM, XPS, and DRS. XRD patterns showed that the crystal structure of Pt–TiO2 still remained as anatase phase. The UV–vis spectra indicated that Pt promoted the absorption of visible light. The XPS measurements reveal that platinum particles are present mainly in metallic form. AFM and HR-TEM analysis revealed the presence of nonspherical shaped platinum nanoparticles of the diameter 3–12 nm. Pt–TiO2 on irradiation induces a combined redox reaction with nitroarene and alcohol and this is followed by condensation–cyclization of aniline and oxidation products to give 2-methylquinolines.
The cesium salts supported on γ-Al2O3 were highly active catalysts for the Michael addition of diethyl malonate (1) to methyl acrylate (2) in toluene as solvent. The use of a limited amount of 2 gave diethyl [2-(methoxycarbonyl)ethyl]malonate (3), however the formation of diethyl bis[2-(methoxycarbonyl)ethyl]malonate (4) was enhanced by the increase in amounts of 2. Catalytic activities were easily recovered by the calcination of used catalysts. IR and XRD observations indicate that the active catalytic species are Cs2CO3 on Al2O3. The use of malononitrile enhanced the formation of the diadduct as principal products by addition to methyl acrylate. Other methyl acrylates, such as methyl methacrylate and methyl crotonate, gave low yield of the products.
Layered silicate RUB-51 with half-sodalite cages was silylated with dichlorodimethylsilane and trichloromethylsilane. RUB-51, which possesses two confronting Si–O−/Si–OH groups on the interlayer surface, was reacted with bi/tri-functional silylating agents to induce bidentate silylation. RUB-51 silylated with dichlorodimethylsilane was delaminated through ultrasonication in cyclohexane. Layered octosilicate, which also possesses two confronting Si–O−/Si–OH groups to form a bidentate state, was reacted with the same silylating reagents. The comparison of these silylated products derived from two different layered silicates reveals that the structures of silylated interlayer surfaces are varied by the arrangement of the two Si–O−/Si–OH groups. Silylated RUB-51 possesses zigzag grooves on the layer surfaces which will be useful for silicate-based nanomaterials design.
A single bacterium in an aqueous Ag nitrate solution was optically trapped by focusing a near-infrared laser beam, and then Ag nanoaggregates were formed on the bacterium by focusing a green laser beam at the bacterium. We obtained surface-enhanced Raman scattering signals from a focal area on a single bacterium.
Small Pt nanoparticles were deposited on bifunctional CeO2/ZSM-5 support combining noble metal stabilizing ability and adsorptive enrichment of organic molecules. The highly efficient thermal catalytic decomposition of methanol as a model compound of VOC can be achieved under mild conditions by Pt/CeO2/ZSM-5.