A representation of the polarization term in the interaction energy between a molecule and a point-like charge

The interaction energy of a molecule M with a point-like charge q can be partitioned into simpler contributions, two of which can be expressed in terms of the charge distribution _M of the sole M. The first term, qV(r), represents the interaction of q with the undistorted charge _M ⁰ of M while the second q ² P(r) gives the additional contributions due to the polarization of _M ⁰ under the influence of the charge q placed at the point r. In this paper we investigate the possibility of getting an inexpensive and sufficiently accurate analytical representation of P(r) over the whole space outside the van der Waals volume of M.     

Conductive characteristics of radical‐bearing polythiophenes using a microcomb‐shaped electrode

The electric conductivity of π‐conjugated and radical‐bearing polymers, i.e., polythiophenes bearing pendant galvinoxyl and phenoxyl radical groups, was measured using a microcomb‐shaped electrode. The electric conductivity was found to be enhanced by the radical content in the polymer. The infrared (IR) and Raman spectroscopies suggested a structural change from an aromatic form to a quinoid one in the polythiophene backbone by the phenoxyl radical generation. The effect of the pendant galvinoxyl radical's unpaired electron on the electric conductivity of the polythiophene was discussed by comparing the conductivity of a radical‐bearing polystyrene and a polythiophene mixed with low‐molecular radical molecules. Copyright © 2007 John Wiley & Sons, Ltd.     

1,1-二氟乙烷和1,2-二氟乙烷分子内原子间非键相互作用

用从头算势诱导极小二乘拟合(PD/LSF)和(exp-6-1)函数研究了1,1-二氟乙烷和1,2-二氟乙烷分子内非键原子间的相互作用。计算结果表明, 同分异构体的能量稳定性差, 在于分子内非键原子间的相互作用。该模式提供了一种简单、实用的研究分子内非键相互作用的方法。     

Inter- and intramolecular potential for the N-formylglycinamide-water system. A comparison between theoretical modeling and empirical force fields

An intramolecular NEMO potential is presented for the N-formylglycinamide molecule together with an intermolecular potential for the N-formylglycinamide-water system. The intramolecular N-formylglycinamide potential can be used as a building block for the backbone of polypeptides and proteins. Two intramolecular minima have been obtained. One, denoted as C5, is stabilized by a hydrogen bonded five member ring, and the other, denoted as C7, corresponds to a seven membered ring. The interaction between one water molecule and the N-formylglycinamide system is also studied and compared with Hartree-Fock SCF calculations and with the results obtained for some of the more commonly used force fields. The agreement between the NEMO and SCF energies for the complexes is in general superior to that of the other force fields. In the C7 region the surfaces obtained from the intramolecular part of the commonly used force fields are too flat compared to the NEMO potential and the ab initio calculations. We further analyze the possibility of using a charge distribution obtained from one conformation to describe the charge distribution of other conformations. We have found that the use of polarizabilities and generic dipoles can model most of the changes in charge density due to the different geometry of the new conformations, but that one can expect additional errors in the interaction energies that are of the order of 1 kcal/mol.     

New unsymmetrical difluoroaromatic compounds and estimation of their reactivities in nucleophilic substitution

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 C_ipso 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 C_ipso atom higher than 0.08 e, are sufficiently activated to be used for the preparation of high-molecular-weight polyethers.     

三乙胺与2-氯-5-甲氧基对苯醌光电子转移反应的CIDNP研究

用化学诱导动态核极化（CIDNP）方法研究了三乙胺与2-氯-5-甲氧基对苯醌在 C6D6，CH3CN溶剂中的反应机理，实验结果表明反应过程中首先形成基态电荷转移 络合物（CTC），在CD3CN中，光照电荷分离形成离子自由基对，使三乙胺亚甲基产 生发射极化信号。同时用UV-vis实验证实CTC的存在。     

Yb~(3+):Cs_2NaYbCl_6和Yb~(3+):Cs_2NaYbBr_6的能级

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。     

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

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     

Potential of zero total charge of platinum single crystals: A local approach to stepped surfaces vicinal to Pt(111)

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.