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排序方式: 共有252条查询结果,搜索用时 15 毫秒
111.
112.
Yamashita M Ono T Matsunaga S Sasaki M Takaishi S Iwahori F Miyasaka H Sugiura KI Kishida H Okamoto H Tanaka H Hasegawa Y Marumoto K Ito H Kuroda S Kimura N 《Inorganic chemistry》2003,42(24):7692-7694
This communication will describe the electron doping effect into Ni(III) complexes by Cu(II) ions, [Ni(1-x)Cu(x)(chxn)(2)Br]Br(2-x) (x = 0.038 and 0.101) by using an electrochemical oxidation method. A drastic increase of electrical conductivity as well as a new absorption band around 0.5 eV in single crystal reflectance spectra was observed by doping Cu(II) ions, indicating the electron doping was successfully made. An ESR result shows unpaired electrons locate in the d(x2-y2) orbitals of Cu(II) and have almost no interaction with those of other ions. 相似文献
113.
Crystal structure parameters were determined for the delafossite type compound CuAlO2 at 295, 450, 600, 750, 900, and 1200 K with single crystal high temperature X-ray diffraction technique. Anisotropic refinements result in conventional R values of 0.021, 0.027, 0.029, 0.030, 0.032, and 0.036 at respective temperatures. Crystals of CuAlO2 have the rhombohedral space group with a = 2.8584(7), c = 16.958(3) Å and Z = 3 at 295 K. The mean thermal expansion coefficient for the dimension a is 11.0 × 10?6 K?1 about three times larger than 4.1 × 10?6 K?1 for c. In the structure, the AlO6 octahedra are linked by their OO edges and form AlO2 layers perpendicular to the c axis with the thickness corresponding to the height of an octahedron. With increasing temperature, the AlO6 octahedra expand along the directions of the basal plane, while expansion scarcely occurs along the c axis. The Cu atom lying between the AlO2 layers shows a large anisotropic behavior in the thermal vibration. The temperature factor for Cu atom in the basal plane becomes very large (0.044 Å2) at 1200 K, but the ratio of the temperature factor perpendicular to c to that parallel to c does not change appreciably with increasing temperature. 相似文献
114.
Kawasaki T Sato M Ishiguro S Saito T Morishita Y Sato I Nishino H Inoue Y Soai K 《Journal of the American Chemical Society》2005,127(10):3274-3275
Right- and left-handed circularly polarized light (CPL) has been proposed as one of the origins of homochirality of biomolecules. However, the enantiomeric excess induced by CPL has been only very low (<2% ee). We found the unprecedented example of asymmetric autocatalysis triggered directly by a chiral physical factor, that is, right- and left-handed CPL, leading to a near enantiopure compound. Asymmetric photolysis of racemic pyrimidyl alkanol by r-CPL irradiation followed by asymmetric autocatalysis affords (R)-pyrimidyl alkanol with >99.5% ee. On the other hand, irradiation with l-CPL affords (S)-pyrimidyl alkanol with >99.5% ee. Thus, chiral physical power, such as CPL, in conjunction with asymmetric autocatalysis, provides a highly enantioenriched compound. 相似文献
115.
116.
H. Kodama T. Miyajima M. Mori M. Takahashi H. Nishimura S. Ishiguro 《Colloid and polymer science》1997,275(10):938-945
The influence of added sodium chloride concentration levels on the acid-dissociation equilibria of a weakly acidic linear
polyelectrolyte and a conjugate acid of weakly basic linear polyelectrolyte has been investigated potentiometrically by use
of polyacrylic acid (PAA) and poly(N-vinylimidazole) (PVIm) as examples of polyelectrolytes. Both equilibria are strongly
influenced by the degree of dissociation of the polyacids as well as the concentration levels of sodium chloride due to an
electrostatic effect originating from the negatively or positively charged polymer surfaces. These have been analyzed in a
unified manner by taking accounts of two-phase properties of the charged linear polyions. Distribution of counterions and
coions between a polyelectrolyte phase formed around the polymer skeleton and a bulk solution phase has been rationalized
by a Donnan’s relation. Introduction of a volume term for the polyelectrolyte phase permits definition of averaged concentrations
of mobile ions in the vicinity of the polyion molecules, which enables us to define hypothetical intrinsic acid-dissociation
constants in the polyion domain. The intrinsic constants estimated by extrapolation of apparent acid-dissociation constants
at zero-charge state are in good agreement with the acid-dissociation constants of the monomer analogs of the polymers, i.e.,
acetic acid for PAA and imidazole for PVIm, respectively. The difference between the apparent and intrinsic acid-dissociation
constants for PVIm was much higher than that for PAA at defined degree of dissociation of the polyacids, even though the separations
of the functionalities fixed on the linear polymers are approximately equal to each other.
Received: 4 February 1997 Accepted: 26 May 1997 相似文献
117.
Umebayashi Y Shin M Kanzaki R Ishiguro Si 《Journal of colloid and interface science》2001,237(2):167-173
Formation of cobalt(II)-thiocyanato complexes in nonionic surfactant solutions of poly(ethylene oxide) type with varying poly(ethylene oxide) chain lengths of 7.5 (Triton X-114), 30 (Triton X-305), and 40 (Triton X-405) has been studied by titration spectrophotometry and calorimetry at 298 K. Data were analyzed by assuming formation of a series of ternary complexes Co(NCS)(n)Y(m)((2-n)+) (Y=surfactant) with an overall formation constant beta(nm). In all the surfactant systems examined, data obtained can be explained well in terms of formation of Co(NCS)(+) and Co(NCS)(2) in an aqueous phase (aq), and Co(NCS)(4)Y(2-) in micelles, and their formation constants, enthalpies, and entropies have been determined. The beta(41)/beta(20) ratio increases and the corresponding enthalpy becomes significantly less negative with an increasing number of ethylene oxide groups. This suggests that micelles of these nonionic surfactants have a heterogeneous inner structure consisting of ethylene oxide and octylphenyl moieties. Indeed, on the basis of molar volumes of ethylene oxide and octylphenyl groups, intrinsic thermodynamic parameters have been extracted for the reaction Co(NCS)(2)(aq)+2NCS(-)(aq)=Co(NCS)(4)Y(2-) (Delta(r)G degrees, Delta(r)H degrees, and Delta(r)S degrees ) at each moiety. The Delta(r)G degrees, Delta(r)H degrees, and Delta(r)S degrees values are -16 kJ mol(-1), -15 kJ mol(-1), and 3 J K(-1) mol(-1), respectively, for the ethylene oxide moiety, and -15 kJ mol(-1), -70 kJ mol(-1), and -183 J K(-1) mol(-1) for octylphenyl. Significantly less negative Delta(r)H degrees and Delta(r)S degrees values for ethylene oxide imply that the hydrogen-bonded network structure of water is extensively formed at the ethylene oxide moiety, and the structure is thus broken around the Co(NCS)(4)(2-) complex with weak hydrogen-bonding ability. Copyright 2001 Academic Press. 相似文献
118.
K. Fujii Y. Matsumoto Y. Kaieda D. Kobayashi Y. Umebayashi S. Ishiguro 《Journal of Thermal Analysis and Calorimetry》2006,85(3):567-573
Cobalt(II)
chloro complexation has been studied by titration calorimetry and spectrophotometry
in solvent mixtures of N-methylformamide
(NMF) and N,N-dimethylformamide
(DMF). It revealed that a series of mononuclear CoClnn
(2–n)+
(n=1–4) complexes are formed in the
mixtures of NMF mole fraction x
NMF=0.05
and 0.25, and the CoCl+, CoCl3
–
and CoCl4
2– complexes
in the mixture of x
NMF=0.5,
and their formation constants, enthalpies and entropies were obtained. As
compared with DMF, the complexation is markedly suppressed in the mixtures,
as well as in NMF. The decreasing formation constant of CoCl+
with the NMF content is mainly ascribed to the decreasing formation entropy.
DMF is aprotic and thus less-structured, whereas NMF is protic to form hydrogen-
bonded clusters. In DMF-NMF mixtures, solvent clusters in neat NMF are ruptured
to yield new clusters involving DMF, the structure of which depends on the
solvent composition. The entropy of formation of CoCl+
will be discussed in relation to the liquid structure of DMF, NMF and their
mixtures. 相似文献
119.
Summary A highly sensitive and selective Spectrophotometric method has been developed for the determination of yttrium in aluminium base alloys. The method is based on the red water-insoluble complex formed when yttrium and 1-[(5-methyl-2-pyridyl)azo]-2-naphthol (5-Me--PAN) react in a pH 9.5–11.2 solution. This complex could be extracted into ether (absorption maximum, 530 nm). Beer's law is obeyed up to 1 p. p. m. of yttrium and the molar absorptivity is 6.4 · 104 l · mole–1 · cm–1 at 530 nm.
Zusammenfassung Eine hochempfindliche und selektive spektrophotometrische Methode zur Bestimmung von Yttrium in Aluminiumlegierungen wurde ausgearbeitet. Sie beruht auf der Bildung der roten, wasserlöslichen Komplexverbindung des Yttriums mit 1-[(5-Methyl-2-pyridyl)azo]-2-naphthol(5-Me--PAN) bei pH 9,5–11,2. Diese Verbindung läßt sich mit Äther extrahieren und hat ein Absorptionsmaximum bei 530 nm. Das Beersche Gesetz ist bis zu 1 ppm Yttrium erfüllt. Die molare Extinktion beträgt 6,4 · 104 1 · Mol–1 cm–1 bei 530 nm.相似文献
120.
To clarify the mechanism of oral toxicity of ricin, the interaction of ricin with the epithelial cells isolated from rat small intestine was compared in vitro with those of other plant lectins by two different determinations, i.e., viability and cytotoxicity. After incubation of the cells for 1 h at 37 degrees C with ricin, B-chain, castor bean hemagglutinin (CBH), soybean agglutinin (SBA), wheat germ agglutinin (WGA), concanavalin A (Con A), and peanut agglutinin (PNA), respectively, followed by staining with trypan blue, ricin and ricin B-chain as well as CBH and SBA were found to have effectively reduced the number of viable cells. On the contrary, only ricin inhibited protein synthesis in the cells and the effect was blocked by D-galactose. Additional experiments employing [125I]-labeled ricin strongly suggested that ricin was first bound via its B-chain to the galactosyl residues on the cell surface followed by internalization into cells as the whole 62 kDa molecule. These results infer first that ricin, as well as other lectins mentioned above, was able to reduce viability of the epithelial cells of rat small intestine by direct binding to the cell surface. The second effect, specific to ricin, was the inhibition of cellular protein synthesis. 相似文献