自组装体系中分子间相互作用对其电化学行为的影响

在电化学研究中,自组装体系是研究电子传递的理想平台。功能化烷硫醇衍生物的自组装尤其受到普遍关注。众多研究工作表明,这些电活性物种之间或多或少地存在相互作用。了解和评价分子间相互作用对电化学行为的影响至关重要,本文将结合本课题组的工作,综述了自组装体系中分子间相互作用对其电化学行为的影响的研究进展,并尝试论述其机理。     

电化学调制时间分辨紫外可见光谱技术及其在电显色研究中的应用

七十年代发展起来的电化学现场(in situ)谱学技术将电化学学科的研究推向分子水平。随着研究深入到分子动态过程,时间分辨谱学技术愈显得重要。紫外可见光谱是检测含π电子、非键电子(如N,O,S,卤素原子)基因、无机配合物分子和电荷转移复合物分子的重要手段。包含这些基团的体系在电化学和生命科学中广泛存在,认识其动态行为意义重大。但目前快速扫描法测量一条紫外可见光谱,最快只能达5ms。近年来,发展起了一种新型光谱探测仪器——光多道分析仪(Optical Multichannel Analyzer,OMA)。其核心由自扫描光敏二极管列阵或光导摄象管构成,能够对多个检测通道(象元)同时完成光电转换。它具有测量速度快、灵敏度高的优势。     

浓NaCl介质中铁阳极溶解时的电位振荡

电化学体系中电位及电流的周期性振荡现象早有发现,对于这些振荡行为的解释多数均涉及到金属的钝化或过渡钝化及固体盐膜的生成^[1,2].本文采用旋转圆盘电极研究了铁在浓NaCl溶液中阳极溶解时的电位振荡行为,并试图应用非保护性多孔膜的生成和溶解以及Fe²⁺的扩散过程来说明这些现象。     

电化学石英晶体微天平应用研究和背景扣除

基于用循环伏安法研究非理想可逆体系时,电极本身的氧化峰电量与还原峰电量存在一比值。据此建立了一种用于电化学石英晶体微天平应用研究的背景扣除新方法。用这种方法研究了腺嘌呤、腺苷、腺苷一磷酸在金电极上的电化学氧化行为。结果表明:3种活性分子均能在1.2V左右氧化,对应的氧化电流大小顺序为:腺嘌呤>腺苷>腺苷一磷酸,氧化过程的电子转移数为6。     

表面增强拉曼光谱研究电化学中的共吸附现象

在电化学研究中,共吸附是一种普遍而又很复杂的界面现象,参与共吸附的各物种之间以及它们与表面之间的作用在不同体系中有着本质上的不同。用常规电化学手段难以对共吸附行为进行详细分析,本文表明应用表面增强拉曼光谱(SERS)技术分析在这些体系中的SERS谱图同电化学参数的关系可以对共吸附现象作更深入的描述和分类。从Ag电极上获得SERS结果来看,可以分为两大类型的共吸附体系。     

电化学现场时间分辩FTIR反射光谱和程序电位阶跃暂态响应信号同步检测系统

应用弛豫（或暂态）方法研究电极过程动力学始于五十年代。由于通过对暂态实验数据的解析能够获得反应速度常数、扩散系数、传递系数、交换电流密度等参数,从而唯象地描述电化学反应动力学,这一研究领域至今仍然十分活跃。从八十年代发展起来的电化学现场红外光谱为研究电化学反应机理提供了分子水平上的数据,从而深化了对速度控制步骤等细节的认识。近几年来我们通过发展时间分辨电化学现场ＰＴＩＲ光谱和程序电位阶跃技术成功地在分子水平上研究不可逆电化学反应的动力学,获得中间体或产物的生成速率。显然,结合时间分辨红外光谱的信息和程序电位阶跃获得的数据将对电化学反应的机理和动力学有更深刻的认识．迄今为止,这两类研究都是分别进行的．时间分辨红外光谱必须使用“薄层电解地”,而暂态方法则应用常规的电解池,这导致了实验条件的不一致,从而对实验数据解析产生分歧．理想的解决办法是两种研究方法都使用同一红外“薄层电解池”,并且同步检测电化学反应体系的电响应（电压、电流）和光响应（红外光谱）信号．本文报道了我们建立的同步检测系统,并通过研究甲酸在Ｐｔ电极上的氧化过程对该系统进行检验,实验结果同时显示了红外“薄层电解池”的快速响应特性．     

聚集诱导发光材料与纳米晶复合体系动力学新进展北大核心CSCD

近期,中科院大连化物所吴凯丰研究员团队将聚集诱导发光分子(AIEgen)嫁接到纳米晶表面,并研究了这一复合体系的激发态动力学,发现这一复合体系中AIEgen的非辐射分子内运动可以得到有效抑制,这一普适性现象可用于构建各类多功能发光材料。相关工作发表于《物理化学快报》(Journal of Physical Chemistry Letters)上。传统的染料分子由于芳香环的π-π堆积通常表现出聚集诱导猝灭现象(ACQ),阻碍了这些染料分子在不良溶剂和固体发光器件中的广泛应用。AIEgen则刚好相反:在良溶剂中,各种分子内运动可耗散激发态能量,导致发光效率极低;在不良溶剂或者固态薄膜中,分子的团聚有效抑制了上述非辐射分子内运动,表现出强烈的发光行为。     

从表面电化学实验参数理解活性基团的微观结构

从分子水平上理解电子传递中电活性基团的结构变化能够直接促进我们对电化学、分子/纳米电子学、生命过程中电子传递的认识。表面电化学是经典的宏观实验方法,从宏观的实验数据中也可以了解分子结构和电活性基团所处的微环境的信息。对此,本文从表面电化学的转移系数、表观转移电子数和重组能三个方面进行了介绍。表面电化学的转移系数的变化规律可以用来指示分子间的相互作用,表观转移电子数能够给出生物大分子基团间的连接信息,重组能可以反应出电活性中心溶剂化环境的变化。本文旨在充分发挥宏观实验方法在分子电化学方面的研究价值。     

电化学现场时间分辩FTIR反射光谱和程序电位阶跃暂态响应信号同步检…

应用弛豫（或暂态）方法研究电极过程动力学始于五十年代，由于通过对暂态实验数据的解析能够获得反应速度常数、扩散系数、传统递系数、交换电流密度等参数，从而唯象地描述电化学反应动力学，这一研究领域至仍然十分活跃，从八十年代发展起来的电化学现场红外光为研究电化学应机理提供了分子水平上的数据，从而深化了对速度控制步骤等细节的认识，近几年来我们通过发展时间分辨电化学ＦＴＩＲ恍谱和程度阶跃技术成功地在分子水平上     

超重力场中水溶液的电化学反应特性

以Fe3+/Fe2+电对体系和铁氰酸根离子为研究对象, 分别采用循环伏安法、线性扫描伏安法和计时电流法等考察了在超重力条件下Fe3+/Fe2+电对体系和铁氰化钾离子的电化学行为, 为认识和发展超重力场中电化学反应过程的研究提供了一定的理论及实验依据.     

On the Mavroyannis–Stephen relativistic long-range interaction energy term between optically active molecules

The relativistic long-range intermolecular interaction energy term of Mavroyannis and Stephen is estimated for some amino acids by using optical rotatory dispersion data and for hexahelicene by using theoretical values of excitation energies and rotational strengths. The result shows that the interaction energy may be significant for the interaction between some essentially dissymmetric chromophores such as hexahelicene, but that it is unimportant for other cases.     

Role of electrostatic interactions for the domain shapes of Langmuir monolayers of monoglycerol amphiphiles

The role of electrostatic interaction in the domain morphology of amide, ether, ester, and amine monoglycerol monolayers (abbreviated as ADD, ETD, ESD, and AMD, respectively) with systematic variation in the molecular structure of the headgroup region is investigated. Experimental studies using Brewster angle microscopy (BAM) and grazing incidence X-ray diffraction (GIXD) show that the characteristic features of the condensed monolayer phase, such as domain morphology, crystallinity, and lattice parameters, are very different for these monoglycerols. Therefore, the intermolecular interactions of the four amphiphilic monoglycerols are investigated in detail. First, the dipole moments of four monoglycerols of similar structure but with different functional groups are calculated by a semiempirical quantum mechanical technique. The dipole moments for monoglycerols follow the sequence AMD < ETD < ESD < ADD for the population of conformers of compounds investigated. The dipolar repulsion energies for the amphiphilic monoglycerols are also calculated for different possible mutual orientations between the dipoles. The calculated dipolar energies also follow the same trend for different possible headgroup orientations. These results can explain the domain shape of the monoglycerols observed experimentally. Second, ab initio calculations on the basis of the HF/6-31G** method are performed for representative monoglycerol headgroup segments. The results show that the intermolecular interaction energy related to dimer formation follows the order ETD < ESD < AMD < ADD segments, similar to that observed in experiment except in the case of the AMD segment. The relative importance of intra- and intermolecular hydrogen bonding in dimers is analyzed. The enhanced role of the intermolecular interaction relative to intramolecular interaction in the case of AMD contributes to the relatively high intermolecular interaction energy for the particular conformation of the dimer of AMD segment as observed from ab initio calculation. The present work shows that the variations in headgroup molecular structure alter drastically the domain shape, and the theoretical calculations conclusively reveal the important role of the electrostatic interactions for the mesoscopic domain architecture.     

A molecular theoretical derivation of the Landau free energy of chiral smectic C liquid crystals

A molecular theoretical derivation of the Landau free energy of chiral smectic C liquid crystals is presented on the basis of a molecular theoretical approach. The excess free energy concerned with the ferroelectric helicoidal structure is derived within a mean field approximation. Several material constants such as the Curie temperature, the elastic constant, the helical pitch, the piezo- and flexoelectric constants and the dielectric susceptibility are expressed in terms of some effective intermolecular interaction parameters between molecules. A molecular theoretical consideration of the chiral smectic C-smectic A transitions is given in comparison with a few previous works. By comparing with some available experimental data for DOBAMBC, effective interaction parameters are numerically estimated.     

分子间相互作用的量子化学研究方法

分子间相互作用是一类十分重要的作用, 这类作用的实验和理论研究越来越受到化学家、生物学家、材料科学家等的重视。本文综述了这种相互作用的量子化学研究现状和特点, 主要集中于常见的3 种量子化学方法。并对该领域的研究前景作了展望。     

Cobalt(II)/(III) complexes bearing a tetradentate thiosemicarbazone: Synthesis,experimental and theoretical characterization,and electrochemical and antioxidant properties

New cobalt complexes, Co1 and Co2 , were synthesized starting from acetylacetone-S-methylthiosemicarbazone. The square planar cobalt(II) and octahedral cobalt(III) complexes were characterized by FT-IR, UV–visible, ¹H NMR, and X-ray diffraction spectroscopies and mass spectrometry. Frontier orbitals of the complexes were theoretically obtained to better understand the complex structures and intermolecular interactions. The electrochemical behaviors of Co1 and Co2 were investigated and the results were evaluated by comparing with each other and with similar published compounds to determine their possible usage in various electrochemical technologies, such as energy storage devices, electrocatalysts, and electrosensors. Metal-based oxidation at around 0 V and metal-based reduction at around −1.0 V indicated that these complexes are valuable for the proposed applications. By determining the trolox equivalent antioxidant capacity and the radical scavenging activity of the cobalt complexes, the compatibility between the antioxidant qualification, redox, and theoretical calculation results was discussed.     

Energy decomposition analysis based on a block-localized wavefunction and multistate density functional theory

An interaction energy decomposition analysis method based on the block-localized wavefunction (BLW-ED) approach is described. The first main feature of the BLW-ED method is that it combines concepts of valence bond and molecular orbital theories such that the intermediate and physically intuitive electron-localized states are variationally optimized by self-consistent field calculations. Furthermore, the block-localization scheme can be used both in wave function theory and in density functional theory, providing a useful tool to gain insights on intermolecular interactions that would otherwise be difficult to obtain using the delocalized Kohn-Sham DFT. These features allow broad applications of the BLW method to energy decomposition (BLW-ED) analysis for intermolecular interactions. In this perspective, we outline theoretical aspects of the BLW-ED method, and illustrate its applications in hydrogen-bonding and π-cation intermolecular interactions as well as metal-carbonyl complexes. Future prospects on the development of a multistate density functional theory (MSDFT) are presented, making use of block-localized electronic states as the basis configurations.     

Column selectivity from the perspective of the solvation parameter model

The solvation parameter model is a useful tool for delineating the contribution of defined intermolecular interactions to retention of neutral molecules in separation systems based on a solute equilibrium between a gas, liquid or fluid mobile phase and a liquid or solid stationary phase. The free energy for this process is decomposed into contributions for cavity formation and the set up of intermolecular interactions identified as dispersion, electron lone pair, dipole-type and hydrogen bonding. The relative contribution of these interactions is indicated by a series of system constants determined by the difference of the defined interaction in the two phases. The interpretation of these system constants as a function of experimental factors that affect retention in the chromatographic system provides the connection between relative retention (selectivity) and the control variables for the separation system. To aid in the understanding of these processes we perform an analysis of system constants for gas chromatography, liquid chromatography, supercritical fluid chromatography and micellar electrokinetic chromatography as a function of different experimental variables as a step towards gaining a theoretical understanding of selectivity optimization for method development.     

Measurements of the hyperfine structure of hydrogen dimers in zero magnetic field

Measurements of the zero magnetic field hyperfine spectra of the ortho—para and the ortho—ortho hydrogen dimers are presented. Comparison with the theoretical spectra yields expectation values for the intermolecular separation, rotational constant and anisotropic intermolecular interaction strengths in the dimers.     

均聚物/共聚物共混体系的相行为研究进展

通过控制均聚物与共聚物共混过程中的相行为,能够得到许多性能优异的材料。本文从理论和实验两方面总结了影响均聚物／共聚物共混体系相容性和形态结构的因素,主要包括均聚物的分子量、浓度,共聚物的组成、结构、浓度,与均聚物相应的共聚物组分的分子量,共聚物分子内的相互作用,均聚物与共聚物分子间的相互作用等。     

醇类溶剂溶剂化显色极性的理论分析

对一系列醇类溶剂分子进行了理论计算,运用多元线性回归分析方法从分子间相互作用的角度对四种溶剂化显色极性参数(E~T^N,π^*,Py和SPP)进行了理论分析。结果表明,对醇类溶剂而言,参数E~T^N和SPP实质上主要反映的是溶剂的氢键酸性性质;参数π^*中虽然包含了溶剂的极性因素,但同时与溶质-溶剂分子间的电荷转移相互作用有着密切的关系;而参数Py则较好地反映了溶剂的极性性质。