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151.
We have investigated the photon-stimulated ion-desorption from deuterated formic acid (DCOOD) monolayer chemisorbed on Si(100) crystal by applying a photoion-photoion-coincidence technique. The true-coincidence yields of an ion pair C+---D+ are given in the photon energy range (275–400 eV) above the C 1s absorption edge. The partial ion yields and Auger electron yields re presented for comparison. It was found that the multielectron (shake-off) excitation promotes the multiple bond-breaking of the adsorbate and the ion pair C+–D+ desorption events. 相似文献
152.
Dr. Meicheng Wen Dr. Kohsuke Mori Dr. Yasutaka Kuwahara Prof. Taicheng An Prof. Hiromi Yamashita 《化学:亚洲杂志》2018,13(14):1767-1779
Single‐site photocatalysts generally display excellent photocatalytic activity and considerably high stability compared with homogeneous catalytic systems. A rational structural design of single‐site photocatalysts with isolated, uniform, and spatially separated active sites in a given solid is of prime importance to achieve high photocatalytic activity. Intense attention has been focused on the design and fabrication of single‐site photocatalysts by using porous materials as a platform. Metal–organic frameworks (MOFs) have great potential in the design and fabrication of single‐site photocatalysts due to their remarkable porosity, ultrahigh surface area, extraordinary tailorability, and significant diversity. MOFs can provide an abundant number of binding sites to anchor active sites, which results in a significant enhancement in photocatalytic performance. In this focus review, the development of single‐site MOF photocatalysts that perform important and challenging chemical redox reactions, such as photocatalytic H2 production, photocatalytic CO2 conversion, and organic transformations, is summarized thoroughly. Successful strategies for the construction of single‐site MOF photocatalysts are summarized and major challenges in their practical applications are noted. 相似文献
153.
Treatment of Mn(CO)5SiTolp2H (2) with an excess of LiAlH4, NaBH4, or NaBH3(CN) in THF at room temperature gave hydrosilane H---SiTolp2H in high yield together with Mn2(CO)10. No reduction of CO ligands was observed. On the other hand, treatment of 2 with an excess of Red-Al (=Na[(CH3OCH2CH2O)2AlH2]) in toluene and subsequent addition of aqueous acidic solution afforded alkylsilanols (CH3)SiTolp2(OH) and (C2H5)SiTolp2(OH). Treatment of the reaction mixture of 2 and Red-Al with LiAlH4 in diethyl ether instead of hydrolysis gave alkylhydrosilanes (CH3)SiTolp2H and (C2H5)SiTolp2H. The methyl and ethyl groups on silicon originate from the CO ligands in 2. These products clearly demonstrate that not only the Si---C coupling, but also C---C coupling occurs efficiently in this reaction. 相似文献
154.
Hiromi Kitano Hiroshi Endo Makoto Gemmei-Ide Mayumi Kyogoku 《Journal of inclusion phenomena and macrocyclic chemistry》2003,47(1-2):83-90
Complexation of various kinds of bisphenols (BPs) with cycloheptaamylose(β-cyclodextrin, β-CD) derivatives (β-CD, hydroxyethyl-β-CD (HE-β-CD), 2,6-di-O-methyl-β-CD (DM-β-CD) and polymerised β-CD (L-Poly-β-CD)) was examined fluorimetrically using2-anilinonaphthalene-6-sulfonic acid (2,6-ANS) as a probe. From the inhibitory effectof BPs on the inclusion of 2,6-ANS by the β-CD derivatives, the associationconstants (Kass) of BPs with the β-CD derivatives were determined.The Kass values for bisphenol B (BPB) with β-cyclodextrin derivatives except for L-Poly-β-CD were always larger than those for other BPs including bisphenol A (BPA), due to the interaction between the non-polar cavity and hydrophobic BPB. Thermodynamic parameters indicated that the entropy change was always largely negative (-90~ -120 J/mol...K in the β-CD system, for example), and the inclusion of bisphenols into the CD cavity was completely enthalpy-driven. The very largely negative entropy change might be mainly due to the tight fixation of guest molecules in the CD cavity, resulting in the loss of freedom of both CD and guest molecules. The effect of the structure of guest and host molecules on the association was also examined. 相似文献
155.
Sunatsuki Y Ohta H Kojima M Ikuta Y Goto Y Matsumoto N Iijima S Akashi H Kaizaki S Dahan F Tuchagues JP 《Inorganic chemistry》2004,43(14):4154-4171
The [Fe(II)(H(3)L)](BF(4))(2).3H(2)O (1) complex was synthesized, where H(3)L (tris[[2-[(imidazole-4-yl)methylidene]amino]ethyl]amine) is a tripodal ligand obtained by condensation of tris(2-aminoethyl)amine and 4-formylimidazole (fim) in a 1:3 molar ratio. Starting from 1, a series of complexes, [Fe(II)(H(1.5)L)](BF(4))(0.5) (2) (=[Fe(II)(H(3)L)][Fe(II)(L)]BF(4)), [Fe(H(1.5)L)]BF(4) (3) (=[Fe(II)(H(3)L)][Fe(III)(L)](BF(4))(2)), [Fe(III)(H(3)L)](BF(4))(3).fim.H(2)O (4), and [Fe(III)(L)].2.5H(2)O (5), has been synthesized and characterized. The single-crystal X-ray structure of each complex has been determined. The Fe(II) compound, 2, and a mixed valence Fe(II)-Fe(III) compound, 3, involve formally hemi-deprotonated ligands, H(1.5)L. The structure of 3 consists of a homochiral two-dimensional assembled sheet, arising from the intermolecular hydrogen bonds between [Fe(II)(H(3)L)](2+) and [Fe(III)(L)](0) (3). All but 5 exhibit spin crossover between low-spin (LS) and high-spin (HS) states. This is a rare case where both Fe(II) and Fe(III) complexes containing the same ligand exhibit spin-crossover behavior. Magnetic susceptibility and M?ssbauer studies showed that 3 has three accessible electronic states: LS Fe(II)-LS Fe(III), HS Fe(II)-LS Fe(III), and HS Fe(II)-HS Fe(III). Compounds 1-3 show the light-induced excited spin-state trapping effect at the Fe(II) sites upon irradiation with green light. The solution magnetic properties, electronic spectra, and electrochemical properties of 1, 4, and 5 were also studied. 相似文献
156.
Kazuyoshi Tanaka Hiromi Kobayashi Mayumi Okada Masahiro Kobashi Tokio Yamabe 《International journal of quantum chemistry》1992,42(1):45-54
Electronic-phase transition associated with the singlet instability problem of the Hartree-Fock solution of the extended system is studied employing the metallic trans-polyacetylene. Concerning the eigenstates of the stability matrix set up for the crystal orbitals at the Fermi level, classification of the electronic phases is attempted and the origin of their emergence in relation to the interelectronic interaction is discussed. 相似文献
157.
Elimination of translational and rotational motions in nuclear orbital plus molecular orbital theory
The nuclear orbital plus molecular orbital (NOMO) theory was developed in order to determine the nonadiabatic nuclear and electronic wave functions. This study presents a formulation to remove the contamination of rotational motion as well as translational motion in the NOMO theory. We have formulated the translation- and rotation-free (TRF)-NOMO theory by introducing the TRF Hamiltonian. The principal moment of inertia, which is the denominator in the rotational Hamiltonian, is expanded in a Taylor series. The zeroth-order of the Taylor expansion corresponds to a rigid-body rotator. The first-order terms contribute the coupling between the vibration and the rotation. Hartree-Fock equations have been derived in the framework of the TRF-NOMO theory. Numerical assessments, which were preformed for H2, D2, T2, mu2 (muon dimmer), and H2O, confirmed the importance of the TRF treatment. 相似文献
158.
Hitoshi Ito Yumi Ohki Yuhei Watanabe Hiromi Sunaga Isao Ishigaki 《Radiation Physics and Chemistry》1993,42(4-6):597-600
Relative sensitivities of endospores of Bacillus pumilus E601, B. subtilis IAM1069, B. megaterium S31 and B. brevis S5 to gamma rays, converted X rays (bremsstrahlung) and electron beams were examined in order to estimate the conditions in which converted X rays kill Bacillus spores. The radiation sensitivities to gamma rays and electron beams of each strain dried on glass fiber filter without additives were found to be almost equivalent, and D values were obtained as follows: 1.5–1.6 kGy for B. pumilus, 1.4–1.5 kGy for B. subtilis, 1.9–2.0 kGy for B. megaterium and 1.6–2.0 kGy for B. brevis. The radiation sensitivities of endospores of each strain to electron beams were slightly lower than those to gamma rays in the dry condition with additives of 2% peptone + 1 % glycerin on glass fiber filters. The increase of radiation resistance in the presence of additives was also observed with X rays, and it was on an intermediate level between those with gamma rays and electron beams. In the dry condition using cellulose filter paper, only the radiation resistances of B. megaterium and B. brevis in the presence of additives B. megaterium and B. brevis in the presence of additives were increased. 相似文献
159.
Kikuchi Y Yamada H Kunimori H Tsukada T Hozawa M Yokoyama C Kubo M 《Langmuir : the ACS journal of surfaces and colloids》2005,21(8):3273-3278
In this study, the aggregation and breakup behaviors of latex particles in shear flow confined between two parallel plates were investigated using an in situ observation apparatus with a laser scanning confocal microscope. To investigate the effects of shear rate and the gap width between two parallel plates on the size and structure of the aggregates in the steady state, the distributions of the projected cross-sectional area and perimeter-based fractal dimension of the aggregates were measured. As a result, the average size of the aggregates decreases as shear rate increases and the gap width decreases due to the hydrodynamic effect acting on the aggregates. The size distributions of the aggregates become narrow as the gap width decreases. In addition, the fractal dimension, that is, the structure of the aggregates, was almost independent of shear rate and the gap width and approximately 1.2, which suggests that the aggregates are relatively compact. 相似文献
160.
A disulfide, which carried two L-phenylalanyl p-nitroanilide (Phe-pNA) moieties at both ends, was prepared by the coupling of 11,11'-dithiodiundecanoic acid (DTUA) with Phe-pNA. The compound obtained (DTUA-Phe-pNA) formed a self-assembled monolayer (SAM) on a gold electrode and vacuum-evaporated gold thin film as proven by cyclic voltammetry, and reflection absorption spectroscopy, respectively. Incubation of alpha-chymotrypsin with the SAM-modified electrode induced both a decrease in anodic and cathodic peak currents (-DeltaIa and -DeltaIc) and an increase in potential difference (DeltaEp) in the cyclic voltammogram of potassium ferricyanide as a probe, which suggested the attack of the enzyme at the amide group between Phe and pNA groups of the SAM, resulting in the formation of an intermediate. The linear relationship between the initial rate of increase in the amount of enzyme bound to the SAM and in both DeltaIa (absolute value of the decrease in anodic peak current) and DeltaEp values was confirmed by the quartz crystal microbalance method. The binding rate of the enzyme to the Phe-pNA SAM was dependent on the surface density of the Phe-pNA group in the SAM. The alpha-chymotrypsin-induced increases in the DeltaIa and DeltaEp values were inhibited by the addition of N-acetyl-D-phenylalanine methyl ester (N-Ac-D-Phe-OMe). In contrast with alpha-chymotrypsin, trypsin did not show a significant increase in the DeltaIa and DeltaEp values upon incubation with Phe-pNA-carrying SAM. These results could be attributed to the specific attack of alpha-chymotrypsin to the amide group in the SAM. The inhibition constant for N-Ac-D-Phe-OMe in the SAM system was quite similar to that in the free substrate system, showing that the enzymatic reaction above the SAM proceeds in a similar way to that in the homogeneous solution system. 相似文献