钴卟啉对有机小分子的手性识别

采用含时密度泛函理论方法研究了手性钴卟啉识别手性生物小分子, 解释了分子结构与光学活性的关系. 通过基组叠加误差(BSSE)校正, Co(III)-卟啉衍生物与(S)-脯氨醇和(S)-2-丁氨之间的作用能分别为310.5和241.6 kJ/mol. 这种较强的分子识别作用起源于主体与客体之间的配位和氢键作用. 具有较大负比旋度的金属卟啉分子对具有较小的正比旋度的生物分子的分子识别作用, 极大地抵消了金属卟啉分子的负比旋度数值. 电子吸收光谱和电子圆二色谱表明, 最低能带起源于主体卟啉环-客体小分子的HOMO-LUMO电荷转移跃迁, 具有负或正的康登效应. 较高能带由配体内部的π→π*电子跃迁所致, 具有一个负的和一个正的康登效应. 最高能带由取代基到卟啉环的p→π*电子跃迁所致, 具有两个负的康登效应.     

纤维素纤维接枝β-环糊精对苯二酚类分子的包络识别性能

用分光光度滴定法在不同温度、不同pH值条件下测定了纤维素纤维接枝β-环糊精与苯二酚类分子形成超分子包合物的表观热力学参数. 化学计量法表明, 纤维素纤维接枝β-环糊精上环糊精与客体苯二酚类分子形成了1∶1的超分子包合物. 从主-客体间包合物的表观热力学参数、尺寸关系、溶液pH值、包合时间等因素讨论了纤维上环糊精对客体苯二酚类分子的分子识别机制. 结果表明, 纤维素纤维接枝β-环糊精上环糊精对苯二酚类分子不同位置羟基具有分子选择性和识别能力.     

环糊精-卟啉超分子体系的构筑及应用进展

环糊精具有分子识别和选择包结客体分子的独特性质,而卟啉具有模拟酶催化、电子转移和光能转移等功能,本工作通过对环糊精-卟啉超分子体系构筑方式的介绍,详细综述了环糊精-卟啉超分子体系在模拟酶催化、生命科学、药物控释、电子转移过程等方面的应用,认为环糊精-卟啉超分子体系具有卟啉和环糊精双重性质的优点,而以键联环糊精-卟啉为主体分子构筑的超分子体系能更有效地模拟生物酶,表现出优异的区域和立体选择性,在仿生催化方面将具有更广泛的应用前景.     

超分子体系中的分子识别研究(Ⅻ)──环糊精及环糊精双核铜配合物对4-取代苯酚的分子识别

用分光光度滴定法在25.0℃时测定了不同pH值下α-,β-,γ-环糊精以及1mol/LNaOH水溶液中α-和β-环糊精双核铜配合物与4-取代苯酚形成超分子配合物的稳定常数.化学计量法表明,主体环糊精及环糊精双核铜配合物与客体4-取代苯酚形成了1：1的超分子配合物.从主-客体间的尺寸关系、pH值、多点识别和诱导契合作用等因素讨论了环糊精及环糊精双核铜配合物对客体4-取代苯酚的分子识别机制.结果表明,β-环糊精双核铜配合物对4-取代苯酚具有特殊的键合能力和分子选择性。     

超分子在质量敏感压电化学传感器中的应用

以质量敏感为分析基础的压电化学传感器,其表面涂层往往决定其对分析物的选择性。超分子作为压电石英晶体涂层,应用主－客体分子识别的原理,显著提高压电化学传感器的选择性。该文详细论述了近十年有关超分子主体化合物在体波和表面波化学传感器的应用,并了涂膜技术及主－客体识别机理。     

30-冠-10对生物极性客体的分子识别和分子开关

用AM1,MNDO和PM3方法对30-冠-10与苯衍生物及其生物活性物质脱氧核糖、核糖和呋喃果糖的超分子配合物进行理论研究,得到配合物的稳定化能,结果表明,冠醚对极性客体具有识别作用,尤其对脱氧核糖的识别效果较好。用INDO／SCI方法计算超分子配合物的电子吸收光谱,计算结果表明,配合物的光谱吸收峰与主体相比发生蓝移。探讨了冠醚和间二苯甲酸配合物的分子开关的形成机理。     

基于主客体识别作用的光控智能超分子体系的研究进展

利用主客体识别作用赋予材料智能化是目前智能材料研究的一个新方向.通过光可以使客体分子发生可逆的结构改变,如偶氮苯可逆的光致顺反异构,结合环糊精主体分子和客体分子之间可逆形成包结物的能力,可以利用光来设计光控的智能超分子体系.基于上述环糊精和客体分子之间的光控制的主客体识别作用,本文从有机小分子、聚合物和表面三个方面综述了近年来基于主客体识别作用的光控智能超分子体系的研究工作,并对该领域的研究前景进行了展望.     

超分子体系中的分子识别研究23.多胺修饰β-环糊精及其铜配合物与萘衍生物的包结配位作用

用荧光光谱滴定法测定了单-[6-(二乙烯三胺)-6-脱氧]-β-环糊精(1)、单-[6-(三乙烯四胺)-6-脱氧]-β-环糊精(2)及其铜配合物(3,4)与一系列萘衍生物在磷酸缓冲溶液(pH 7.2,0.1 mol·dm-3)中,25℃时形成超分子体系的稳定常数,并与母体β-环糊精的配位能力进行了比较.化学计量法表明,四种化学修饰β-环糊精与萘衍生物形成了1:1的超分子配合物.从尺寸适合、几何互补及多点识别等方面讨论了主体化合物对模型底物的分子选择性键合能力.结果表明,疏水相互作用、范德华力、静电相互作用及氢键等多种非共价键弱相互作用协同贡献于超分子配合物的形成,主-客体间的结构匹配在分子受体选择性键合底物形成超分子配合物中起重要作用.     

超分子化合物毛细管电色谱固定相的研究进展

超分子化学是一门研究分子间特定识别能力的新兴学科,超分子化合物所具有的主-客体识别能力为高选择性的色谱分离提供了广阔的发展前景。毛细管电色谱是近年来发展起来的一种高效、高选择性的微分离技术,电色谱固定相是该技术的核心部分,一直是研究的热点。本文综述了1998年以来环糊精、杯芳烃、冠醚以及大环多胺等4种超分子化合物用作毛细管电色谱固定相的研究进展情况。     

基于柱[5]芳烃主客体包结构筑分子响应型超分子水凝胶

主客体相互作用是在水溶液中与大环主体分子形成稳定的包结物的理想驱动力.以功能化的苯并咪唑衍生物为客体(M),水溶性柱[5]芳烃为主体构建了一种分子响应型超分子水凝胶.通过1H NMR, 2D NOESY和扫描电子显微镜(SEM)研究了水凝胶的成凝胶机理.有趣的是,主客体包结作用、柱[5]芳烃间有序的"外腔"π-π相互作用和分层堆积对于获得超分子水凝胶是必不可少的,非共价键相互作用的动态可逆性使凝胶体系对温度变化/化学刺激产生响应.此外,加入竞争性客体己二腈(ADN)/百草枯(PQ)后,柱[5]芳烃基水凝胶可转化为溶胶.因此,该超分子水凝胶可以选择性识别有机分子.     

转动取向影响因素的多元非线性分析

在不同拓扑特征的London-Eying-Polanyi-Sato(LEPS)型势能面上，应用经典轨线法计算了不同动态条件下的58个样本，应用多元非线性分析方法研究了势能面及动态条件对转动取向的影响.结果表明, 对于A＋BC→AB＋C类反应, 反应物分子的质量比、势能面出口处的宽度和相对平动能对产物分子的转动取向有重要作用，且发现不同影响因素之间的乘积对产物的转动取向具有更重要的作用.     

On the molecular structure of uranium dicarbide: T-shape versus linear isomers

A theoretical study of the molecular structure of uranium dicarbide has been carried out employing DFT, coupled cluster, and multiconfigurational methods. A triangular species, corresponding to a (5)A(2) electronic state, has been found to be the most stable UC(2) species. A triplet linear CUC species, which has been observed in recent infrared spectroscopy experiments, lies much higher in energy. A topological analysis of the electronic density has also been carried out. The triangular species is shown to be in fact a T-shape structure with a U-C interaction which can be considered to be a closed-shell interaction.     

Topological analysis of the electronic charge density in the ethene protonation reaction catalyzed by acidic zeolite

In the present work, the distribution of the electronic charge density in the ethene protonation reaction by a zeolite acid site is studied within the framework of the density functional theory and the atoms in molecules (AIM) theory. The key electronic effects such as topological distribution of the charge density involved in the reaction are presented and discussed. The results are obtained at B3LYP/6-31G(**) level theory. Attention is focused on topological parameters such as electron density, its Laplacian, kinetic energy density, potential energy density, and electronic energy density at the bond critical points (BCP) in all bonds involved in the interaction zone, in the reactants, pi-complex, transition state, and alkoxy product. In addition, the topological atomic properties are determined on the selected atoms in the course of the reaction (average electron population, N(Omega), atomic net charge, q(Omega), atomic energy, E(Omega), atomic volume, v(Omega), and first moment of the atomic charge distribution, M(Omega)) and their changes are analyzed exhaustively. The topological study clearly shows that the ethene interaction with the acid site of the zeolite cluster, T5-OH, in the ethene adsorbed, is dominated by a strong O-H...pi interaction with some degree of covalence. AIM analysis based on DFT calculation for the transition state (TS) shows that the hydrogen atom from the acid site in the zeolitic fragment is connected to the carbon atom by a covalent bond with some contribution of electrostatic interaction and to the oxygen atom by closed shell interaction with some contribution of covalent character. The C-O bond formed in the alkoxy product can be defined as a weaker shared interaction. Our results show that in the transition state, the dominant interactions are partially electrostatic and partially covalent in nature, in which the covalent contribution increases as the concentration and accumulation of the charge density along the bond path between the nuclei linked increases.     

Sulfonamide imprinted polymers using co-functional monomers

Molecular imprinted polymers (MIPs) prepared using combination of acrylamide (ACM) and 4-vinylpyridine (4-Vpy) as co-functional monomers exhibited efficient recognition properties in both organic and aqueous media as HPLC stationary phase. The results indicate that amide and pyridine groups in functional monomers formed strong hydrogen-bonding interaction with the template molecule, and specific recognition sites were created within the polymer matrix during the imprinting process. When sulfamethoxazole (SMO) was used as template, a MIP prepared in a polar organic solvent (acetonitrile) using the combination of ACM and 4-Vpy showed better recognition of template than the polymer prepared in the same solvent using the combination of acidic monomer (methacrylic acid) and basic monomer 4-Vpy. On the contrary, when sulfamethazine (SMZ) was used as template, a MIP prepared using the combination of methacrylic acid (MAA) and 4-Vpy showed better recognition of template than the polymer prepared using the combination of ACM and 4-Vpy. Our results indicate that in organic media the degree of retention of the sample molecules on the imprinted polymers was controlled by the hydrogen-bonding interaction between the sample molecules and the polymer, while in aqueous media it was determined to a considerable extent by hydrophobic interactions. In both media the shape, size and the electronic structure of the template molecule were all-important factors in the recognition process.     

A Chemical Recognition Element for Lithium Ions Based on Optical Electronic Absorption

Xerogel samples with entrapped series of four optical absorption chemosensors were prepared by sol-gel process. These materials are proposed as chemical recognition elements of an optical chemical sensor. The roles of the chemosensors play proton-dissociable chromogenic azocrown ethers bearing phenol and two azo groups as parts of macrocycles. Occurrence of the alkali ion—receptor interaction is signalled by the chemosensors changing their electronic absorption spectra. By this way chemosensor 4O-CH₃ is able to distinguish Li⁺ ions from other alkali metal ions present in aqueous solution, if the chemosensor is entrapped in Glymo-silica (1:1) xerogel matrix. The proposed recognition element for Li⁺ has been exposed to the cycles chemisorption—desorption many times. Besides DRIFT spectra of the used xerogel matrices were analyzed.     

Nanoparticles: scaffolds for molecular recognition

Monolayer and mixed-monolayer protected clusters (MPCs and MMPCs) have great potential to combine molecular functionality with the intrinsic properties of nanometer-sized scaffolds. This synergy can be used to create complex functional devices, including redox-active, electronic, or magnetic storage devices, solution-based sensors, and highly efficient catalysts. This review outlines some of the recent developments in nanoscale receptors based on synthetic and nonbiological recognition elements. In these nanoparticle systems, molecular recognition is achieved by covalent attachment of receptors on the nanoparticles coupled with noncovalent interactions to target substrates. Synthetic host-guest systems, hydrogen bonding, change in redox states, pi-pi stacking, rotaxane formation, and ion recognition are the main topics covered in this review.     

基于分子识别的细菌检测研究进展

以抗体-抗原免疫识别、 核酸碱基互补配对识别以及核酸适体-配体识别这3种分子识别方式分类, 综述了近几年基于分子识别的细菌检测研究工作进展, 总结了细菌检测相关研究存在的一些挑战, 并展望了该领域的发展前景.     

The Effects of Substituents on the Geometry of π–π Interactions

We have designed and utilized a simple molecular recognition system to study the substituent effects in aromatic interactions. Recently, we showed that 3‐ and 3,5‐disubstituted benzoyl leucine diethyl amides with aromatic rings of varying electronic character organized into homochiral dimers in the solid state through a parallel displaced π–π interaction and two hydrogen bonds, but no such homochiral dimerization was observed for the unsubstituted case. This phenomenon supports the hypothesis that substituents stabilize π–π interactions regardless of their electronic character. To further investigate the origin of substituent effects for π–π interactions, we synthesized and crystallized a series of 4‐substituted benzoyl leucine diethyl amides. Surprisingly, only two of the 4‐substituted compounds formed homochiral dimers. A comparison among the 4‐substituted compounds that crystallized as homochiral dimers and their 3‐substituted counterparts revealed that there are differences in regard to the geometry of the aromatic rings with respect to each other, which depend on the electronic nature and location of the substituent. The crystal structures of the homochiral dimers that showed evidence of direct, local interactions between the substituents on the aromatic rings also displayed nonequivalent dihedral angles in the individual monomers. The crystallographic data suggests that such “flexing” may be the result of the individual molecules orienting themselves to maximize the local dipole interactions on the respective aromatic rings. The results presented here can potentially have broad applicability towards the development of molecular recognition systems that involve aromatic interactions.     

The role of molecular recognition in charge transport properties of doped polyaniline

Molecular recognition plays a significant role in the counterion-induced processibility, morphological features, and physical properties of doped polyaniline (PANI). The interaction of the counterion and solvent controls the chain conformation and, as a result, the formation of extended and localized electronic states; hence, it holds the key for tuning a wide range of electrical and optical properties of doped PANI. The combined effects of counterion, solvent, and processing conditions tune the metal-insulator transition, temperature dependence of conductivity, magnetoresistance, and so forth in doped PANI. The typical examples are shown in the case of PANI doped by camphor sulfonic acid, 2-acrylamido-2-methyl-1-propane sulfonic acid, and dodecylbenzoyl sulfonic acid.     

D matrix analysis of the Renner-Teller effect: an accurate three-state diabatization for NH2

Some time ago we published our first article on the Renner-Teller (RT) model to treat the electronic interaction for a triatomic molecule [J. Chem. Phys. 124, 081106 (2006)]. The main purpose of that Communication was to suggest considering the RT phenomenon as a topological effect, just like the Jahn-Teller phenomenon. However, whereas in the first publication we just summarized a few basic features to support that idea, here in the present article, we extend the topological approach and show that all the expected features that characterize a three (multi) state RT-type'3 system of a triatomic molecule can be studied and analyzed within the framework of that approach. This, among other things, enables us to employ the topological D matrix [Phys. Rev. A 62, 032506 (2000)] to determine, a priori, under what conditions a three-state system can be diabatized. The theoretical presentation is accompanied by a detailed numerical study as carried out for the HNH system. The D-matrix analysis shows that the two original electronic states 2A1 and 2B1 (evolving from the collinear degenerate Pi doublet), frequently used to study this Renner-Teller-type system, are insufficient for diabatization. This is true, in particular, for the stable ground-state configurations of the HNH molecule. However, by including just one additional electronic state--a B state (originating from a collinear Sigma state)--it is found that a rigorous, meaningful three-state diabatization can be carried out for large regions of configuration space, particularly for those, near the stable configuration of NH2. This opens the way for an accurate study of this important molecule even where the electronic angular momentum deviates significantly from an integer value.