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991.
We propose a theory of electron localization or stabilization by electron localization through the interactions between occupied (i) and vacant (j*) orbitals under certain conditions, which have been believed so far to cause only electron delocalization. Electrons localize when the electrons redistributed by the interaction are more stable in the i-th occupied orbital than in the overlap region: h(ij*) > s(ij*)h(ii) for s(ij*) > 0. Electron delocalization occurs when h(ij*) < s(ij*)h(ii) for s(ij*) > 0. The h(ij*) and s(ij*)h(ii) terms represent the energy of the electrons in the overlap region and the energy of the redistributed electrons in the occupied orbital, respectively. The theory of electron localization is substantiated by the correlation of the C-H bond lengths of fluorinated methanes H(4-n)CF(n) (n = 1, 2, 3) to the electron population of the σ(CH) bonding orbital, and successfully applied to understanding blue-shifting hydrogen bonds in F(3)CH···X (X = CO, N(2), OC, Ne, OC(CH(3))(2)) and designing some proton donors, HCO(2)CH(3) and hypervalent molecules HPF(4) and HSF(5), for blue-shifting hydrogen bonds. 相似文献
992.
Inoki D Matsumoto T Hayashi H Takashita K Nakai H Ogo S 《Dalton transactions (Cambridge, England : 2003)》2012,41(15):4328-4334
Reductive activation of O(2) by H(2) with rhodium terpyridine complexes in H(2)O and CH(3)CN is described and the mechanism is fully elucidated. The rhodium complex extracts electrons from H(2) and reductively activates O(2) to form a peroxo active intermediate. This intermediate is able to oxidise triphenyl phosphine to triphenyl phosphine oxide. A model system constructed in CH(3)CN provides isolable analogues of catalytic intermediates in H(2)O, allowing a detailed look at each step in the catalytic cycle. 相似文献
993.
Kyoungmok Kim Dr. Takahiro Matsumoto Dr. Andrew Robertson Dr. Hidetaka Nakai Prof. Seiji Ogo 《化学:亚洲杂志》2012,7(6):1394-1400
Herein, we report a [NiRu] biomimetic system for O2‐tolerant [NiFe]hydrogenases and demonstrate that electron donation to the [NiRu] center can switch the system between the activation of H2 and O2 through simple ligand effects by using hexamethylbenzene and pentamethylcyclopentadienyl ligands, respectively. Furthermore, we present the synthesis and direct observations of a [NiRu]–peroxo species, which was formed by the oxygenation of a Ni‐SIa model [NiRu] complex, that we propose as a biomimetic analogue of O2‐bound species (OBS) of O2‐tolerant [NiFe]hydrogenases. The [NiRu]–peroxo complex was fully characterized by X‐ray analysis, X‐ray photoelectron spectroscopy (XPS), mass spectrometry, and 1H NMR spectroscopy. The OBS analogue was capable of oxidizing p‐hydroquinone and sodium borohydride to turn back into the Ni‐SIa model complex. 相似文献
994.
We have investigated the high-pressure water (H2O) vapor treatment for poly-crystalline Ge (poly-Ge) thin films, which were prepared by solid phase crystallization. The optical-absorption coefficients of poly-Ge were reduced by the treatment, suggesting that the grain-boundary defects were successfully passivated. But the poly-Ge films were sometimes damaged by the treatment in higher pressure and temperature. Compromised conditions should be pursued between the effective passivation and avoiding the damage. The rapid cooling after the treatment promotes defect passivation but causes structural distortion. The results show that the high-pressure H2O vapor treatment is an effective method for the defect passivation of poly-Ge films. 相似文献
995.
Yoji Akaki Kyohei Yamashita Tsuyoshi Yoshitake Shigeuki Nakamura Satoru Seto Takahiro Tokuda Kenji Yoshino 《Physica B: Condensed Matter》2012,407(15):2858-2860
We characterized AgInS2 thin films prepared by vacuum evaporation. In the case of thin films annealed at 400 °C, diffraction peaks were observed only for the chalcopyrite AgInS2 phase. The chemical composition of the thin films annealed at 400 °C was 26.5 at% Ag, 23.8 at% In, and 49.7 at% S. PL spectra of the AgInS2 thin films at 10.7 K showed peaks at 1.70, 1.80, and 1.83 eV. The PL peak at1.80 eV was attributed to sulfur deficiency. 相似文献
996.
We examine the structure of Maxwell stress in binary fluid mixtures under an external electric field and discuss its consequence. In particular, we show that, in immiscible blends, it is intimately related to the statistics of domain structure. This leads to a compact formula, which may be useful in the investigation of electrorheological effects in such systems. The stress tensor calculated in a phase separated fluid under a steady electric field is in a good agreement with recent experiments. 相似文献
997.
Do Van Truong Nguyen Tuan Hung Takahiro Shimada Takayuki Kitamura 《Surface science》2012,606(15-16):1331-1339
Ferroelectric thin film with the perovskite ABO3 structure have been widely used in technology applications, e.g., actuators in MEMS/NEMS and nonvolatile random access memories (FeRAM). In order to clarify the effect of the shear strain on the ferroelectricity, the PbTiO3 thin film as a typical one is chosen. The focus of this study is to put on the PbO-terminated (1? × ?1) and c(2? × ?2) surfaces and the TiO2-terminated (1? × ?1) surface. Based on ab initio density functional theory calculations with the local density approximation, we have found out that in both the PbO and TiO2-terminated (1? × ?1) models, the ferroelectricity in the PbO layers was enhanced under the positive shear strain while it was suppressed under the negative one. For the TiO2 layers, the ferroelectricity was slightly enhanced and sharply suppressed under the positive and negative shear strains, respectively. In the PbO-terminated (2? × ?2) model, the AFE phase was suppressed by the FE phase under the positive shear strain while the opposite trend was found under the negative shear strain. For the PbO layers, the ferroelectricity was enhanced under the positive and negative shear strains. For the TiO2 layers, the influence of the negative shear strain on the ferroelectricity was larger than that of the positive one. In addition, the ideal strength of the PbTiO3 thin film with the different terminations was investigated as well. 相似文献
998.
The self-assembly of non-toxic well-consumed small caffeine molecules into well-defined structures has important implications
for future medical applications seeking to target the transport of small drugs in human body. Particularly, the solvation
of the microenvironments of the self assembly ultimately dictates the interaction with the drug molecules and their therapeutic
efficacy. We present femtosecond-resolved studies of the dynamics of aqueous solvation within self-assembled dimeric structure
of caffeine molecules. We have placed small hydrophobic probes 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl) 4H-pyran
(DCM), coumarin 500 (C500) into the caffeine dimer to enable spectroscopic examinations of the interior. While molecular modeling
and NMR studies of the probes in the caffeine dimers reveal a well-defined location (stacked in between two caffeine molecules),
dynamical light scattering (DLS), Fourier transform infrared (FTIR) spectroscopy, densimetric and sonometric experiments explore
the structural evolution of the dimer upon complexation with the probes. We have extended our studies in various temperatures
in order to explore structural evolution of the self assembled structure and consequently the dynamics of solvation in the
interior of the dimer. Picoseconds/femtosecond resolved dynamics and the polarization gated spectroscopic studies unravel
the hydration and energetics associated with activated viscous flow of the confined probes. Our studies indicate that the
interior of the caffeine dimer is well-solvated; however, the dynamics of solvation is retarted significantly compared to
that in bulk water, clearly revealing the dimers maintain some ordered water molecules. We have also explored the consequence
of the retarded dynamics of solvation on the photo-induced electron transfer (ET) reaction of a model probe, 2-(p-toluidino)
naphthalene-6-sulfonate (TNS) encapsulated in the dimer. 相似文献
999.
H Shimizu F Jinno A Morohashi Y Yamazaki M Yamada T Kondo S Asahi 《Journal of mass spectrometry : JMS》2012,47(8):1015-1022
We investigated the application of a high-resolution Orbitrap mass spectrometer equipped with an electrospray ionization (ESI) source and a matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) mass spectrometer to the metabolite profiling of a model small interfering RNA (siRNA) duplex TSR#34 and compared their functions and capabilities. TSR#34 duplex was incubated in human serum in vitro, and the duplex and its metabolites were then purified by ion exchange chromatography in order to remove the biological matrices. The fraction containing the siRNA duplex and its metabolites was collected and desalted and then subjected to high-performance liquid chromatography (HPLC) equipped with a reversed phase column. The siRNA and its metabolites were separated into single strands by elevated chromatographic temperature and analyzed using the ESI-Orbitrap or the MALDI-TOF mass spectrometer. Using this method, the 5' and/or 3' truncated metabolites of each strand were detected in the human serum samples. The ESI-Orbitrap mass spectrometer enabled differentiation between two possible RNA-based sequences, a monoisotopic molecular mass difference which was less than 2 Da, with an intrinsic mass resolving power. In-source decay (ISD) analysis using a MALDI-TOF mass spectrometer allowed the sequencing of the RNA metabolite with characteristic fragment ions, using 2,4-dihydroxyacetophenone (2,4-DHAP) as a matrix. The ESI-Orbitrap mass spectrometer provided the highest mass accuracy and the benefit of on-line coupling with HPLC for metabolite profiling. Meanwhile, the MALDI-TOF mass spectrometer, in combination with 2,4-DHAP, has the potential for the sequencing of RNA by ISD analysis. The combined use of these methods will be beneficial to characterize the metabolites of therapeutic siRNA compounds. Copyright ? 2012 John Wiley & Sons, Ltd. 相似文献
1000.
Watanabe H Yoshimura T Kawakami S Sasamori T Tokitoh N Kawabata T 《Chemical communications (Cambridge, England)》2012,48(43):5346-5348
Asymmetric aldol reactions of α-amino acid derivatives via memory of chirality were developed. Chiral oxazolidones with contiguous tetra- and trisubstituted chiral centers were obtained in 78-94% ee by the asymmetric aldol reaction followed by intramolecular acylation. 相似文献