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101.
Keshtov M. L. Rusanov A. L. Keshtova S. V. Petrovskii P. V. Shchegolikhin A. A. 《Russian Chemical Bulletin》2002,51(1):117-123
A series of previously unknown unsymmetrical difluoroaromatic compounds, viz., p-fluorobenzoylphenyl(p-fluorophenyl)-substituted imidazoles, pyrazines, and quinoxalines, were synthesized according to multistep procedures with the use of chloral as the key compound. The reactivities of the resulting difluoroaromatic compounds were estimated based on 19F and 13C NMR spectral data and the results of quantum-chemical calculations. The calculated charge densities on the Cipso atoms correlate linearly with the experimental chemical shifts in the 19F and 13C NMR spectra. Difluoroaromatic compounds, which are characterized by F > –110 and C > 163 and by the charge density on the Cipso atom higher than 0.08 e, are sufficiently activated to be used for the preparation of high-molecular-weight polyethers. 相似文献
102.
103.
本文应用双层点电荷配位场(DSPF)模型计算了Yb~(3+):Cs_2NaYbCl_6和Yb~(3+):Cs_2NaYbBr_6的能级,分析了二体系中Yb~(3+)与Cl~-、Br~-的成键。 相似文献
104.
环己烷中苯甲酰苯胺的双重荧光--分子内电荷转移的直接光谱证据 总被引:2,自引:0,他引:2
自从O Connell等[1]报道苯甲酰苯胺(BA)在EPA玻璃体中异常的长波长荧光发射特性以来, 已有众多学者尝试解释该"异常"荧光的发射态性质[2~12]. Kasha等[2~7]认为长波长荧光是质子转移(PT)和电荷转移(CT)两种激发态发射的叠加, 而Azumaya等[8]则认为发射态只包含分子内扭转电荷转移(TICT)态. 应该指出的是, 在上述研究中, 电荷转移态的指认并无有力的实验事实, 而主要是依据与具有CT双重荧光的对二甲氨基苯甲氰[13,14]的类比. 显然, 有关苯甲酰苯胺的长波长荧光发射态的准确性质仍待实验阐明 相似文献
105.
V. Climent N. García-Araez E. Herrero J. Feliu 《Russian Journal of Electrochemistry》2006,42(11):1145-1160
The electrochemical behavior of platinum single-crystal electrodes is revisited, with special emphasis on the determination
of the potential of zero charge. We show that the measure of the charge displaced during CO adsorption allows the determination
of the potential of zero total charge (PZTC). The estimation of the potential of zero free charge (PZFC) is discussed, with
different degrees of approximation. The application of this methodology to the study of the PZTC of platinum stepped surfaces
vicinal to Pt(111) reveals a marked decrease of the PZTC due to the introduction of surface steps. This effect is interpreted
as the result of the existence of markedly smaller surface potentials localized on step sites. The importance of considering
local aspects of the interface is emphasized with the use of N2O reduction as a sensitive probe to the local structure of the surface. It is proposed that the different local maxima observed
in the absolute value of the reduction current correspond to the local values of PZTC. It is shown that there is, in general,
good agreement between the overall PZTC, obtained from the CO displacement, and that calculated from the local values inferred
from the N2O reduction. Further insight is obtained with the application of the laser-induced temperature jump method. This technique
is useful to calculate the potential of maximum entropy of the double-layer formation. The resulting value of this potential
for Pt(111) is discussed in the light of the PZFC value obtained from different approaches. For stepped surfaces vicinal to
Pt(111), two local maxima in the entropy of the double layer are observed that are close to the local PZTC values estimated
from the N2O reduction. This result suggests the existence of cooperative effects in the organization of the water dipoles close to the
electrode surface.
Published in Russian in Elektrokhimiya, 2006, Vol. 42, No. 11, pp. 1275–1292.
Based on the report delivered at the 8th International Frumkin Symposium “Kinetics of the Electrode Processes,” October 18–22,
2005, Moscow.
The text was submitted by the authors in English. 相似文献
106.
Guldi DM Hirsch A Scheloske M Dietel E Troisi A Zerbetto F Prato M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(20):4968-4979
Control over the interchromophore separation, their angular relationship, and the spatial overlap of their electronic clouds in several ZnP-C(60) dyads (ZnP=zinc porphyrin) is used to modulate the rates of intramolecular electron transfer. For the first time, a detailed analysis of the charge transfer absorption and emission spectra, time-dependent spectroscopic measurements, and molecular dynamics simulations prove quantitatively that the same two moieties can produce widely different electron-transfer regimes. This investigation also shows that the combination of ZnP and C(60) consistently produces charge recombination in the inverted Marcus region, with reorganization energies that are remarkably low, regardless of the solvent polarity. The time constants of electron transfer range from the mus to the ps regime, the electronic couplings from a few tens to several hundreds of cm(-1), and the reorganization energies remain below 0.54 eV and can be as low as 0.16 eV. 相似文献
107.
高温超导体的Cu-O键型和氧上的部分电荷 总被引:2,自引:0,他引:2
多数钙钛矿型化合物是离子型绝缘体,而高温超导化合物则有金属电性,它们是以什么键型为主?对此等人[1]认为用共价或金属成键图像描述高温超导体在化学上更合理,Nepela等人[2]指出超导体临界温度(Tc)随阴离子平均电负性与阳离子平均电负性之差增大而升高.这意味着离子性较强的超导体有较高的人.杨频等问运用晶型键参数方法估算结果表明高温超导体属干部分离子性与部分共价性键.以上不同的结果都是基丁理论处理或估算得到的·本文试图在实验上通过比较不同成键特征的铜化合物的x光电子能潜(*P8)来估计对高温超导性起重要作用的C… 相似文献
108.
桥联双(甲巯咪唑)化合物的合成和配位性能 总被引:3,自引:0,他引:3
研究了桥联双(甲巯咪唑)化合物(Ⅰ_a—Ⅳ_a、Ⅰ_b)的合成和配位性能。UV谱显示Ⅰ_a—Ⅳ_a与UO_2~(2+)离子(硬酸)配位,溶液中形成3:1的配合物。Ⅰ_b与Hg~(2+)、Au~(3+)离子(软酸)配位形成2:1的配合物,用CNDO/2方法计算了各配体分子中原子净电荷密度和HOMO、LUMO能量。 相似文献
109.
Novel carboxylated oligothiophenes as sensitizers in photoelectric conversion systems 总被引:1,自引:0,他引:1
Tan S Zhai J Fang H Jiu T Ge J Li Y Jiang L Zhu D 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(21):6272-6276
Novel carboxylated oligothiophenes with different thiophene units were designed and synthesized as photosensitizers in dye-sensitized solar cells (DSSCs) for efficient opto-electric materials. The introduction of -COOH into thiophene molecules can lead to a red shift of UV-visible absorption, increase light-harvesting efficiency, and enhance photoinduced charge transport by forming efficient covalent bonds to the substrate surface. A red shift of the absorption spectrum of oligothiophene is also achieved by the increase in the number of thiophene units. The DSSCs based on the oligomers have excellent photovoltaic performances. Under 100 mW cm(-2) irradiation a short-circuit current of 10.57 mA cm(-2) and an overall energy conversion efficiency of 3.36 % is achieved when pentathiophene dicarboxylated acid was used as a sensitizer. The incident photo-to-current conversion efficiency (IPCE) has a maximum as high as 80 %. In addition, photovoltage and photocurrent transients show that slow charge recombination in DSSCs is important for efficient charge separation and excellent photoelectric conversion properties of the oligomers. These initial and promising results suggest that carboxylated oligothiophenes are efficient photosensitizers. 相似文献
110.