溴代作用对竹红菌乙素分子性质影响的量子化学研究

用半经验量子化学方法AM1和PM3对竹红菌乙素及其溴代物进行了对比计算,考察了溴代作用对竹红菌乙素分子性质的影响。两种方法所得结果均表明,溴代作用使分子的生成热、前线轨道能级及偶极矩等参数都有所降低,溴代作用也影响了竹红菌乙素分子内氢键的性质,并能使其对光的吸收产生红移。     

Hartree-Fock and Density Functional Theory Studies on the Molecular Recognition of the Cyclodextrin

Cyclodextrins(CD),cyclicoligomersofa-D-glucoseconnectedthroughglycosidical,4bonds,areseductivemoleculesappealingtoresearchersinpureacademicfieldsandappliedtechnologies'.ModelstudiesonCDinclusioncomplexationofferimportantinsightsintoenZyme-substrateillteractionsZandhenceattractgreatattention.Althoughmanyexperimentalapproachesareavailable,molecularmodelingprovidesanimportantalternativewayinstudyingtheCDchemistry'.Duetotheirlargesize,mosttheoreticalstudiesonCDchosemolecularmechanicsormolecula…     

氨基酸、多肽的环糊精化学

本文着重介绍了氨基酸、多肽－环糊精连接物的合成,分子识别和自组装,对环糊精及其衍生物与氨基酸、多肽的包合行为,异构体识别和仿酶合成作了简要概述。     

Quantum Chemical Study on the Thermolysis of Dicyanofuroxan

Recently,thegeometricandelectronicstrUctUreofdicyanofuroxan(3,4-dicyano-l,2,5-oxadiazole-2-oxide)wasstUdiedbyT.Pasinszkiandco-workers,usingabinitiocalcula-honattheHF/6-3lGlevelandx-raycyrstallograPhy.'Beforetheabovework,exPerdrientalstUdyhadsuggestedthatdicyanofuroxancanundergothermolyticcycloreversiontotWomolesofthenovelpenta-atondcmolecule,NCCNO,'whichisofpotentialastrophysicalinterest.Here,theresultSoftheorehcalstUdiesbyAMl'andPM3'methods,usingtheunrestrictedHartree-Fock(UHF)calc…     

Charge-transfer Interaction: A Driving Force for Cyclodextrin Inclusion Complexation

PM3 calculations were performed on the complexation of -cyclodextrin (-CD) with nitrobenzene, benzoic acid, benzoate anion, 4-nitrophenol, and 4-nitrophenolate anion. The results, in agreement with the experimental observations, indicated that the complex -CD-benzoic acid was more stable than -CD-nitrobenzene, and -CD-4-nitrophenolate was more stable than -CD-4-nitrophenol. Frontier orbital analysis suggested that charge-transfer interaction led to such behaviors, and hence constituted a nontrivial driving force in the molecular recognition of -CD.     

1-乙基-3-甲基咪唑四氟硼酸盐离子液体的量子化学研究

The results of the quantum chemistry study of the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIM+BF4-) were reported. The ab initio method and density functional theory (B3LYP method) was used to optimize the stable structure of the gas phase ion pair at the level of 6-311++G** basis set, respectively. An IR spectra for EMIM+BF4- were obtained through the vibrational analysis. The changes of atomic charge assignments have been investigated using the Natural Bond Orbital method. The computational results show that there exist hydrogen bonds and other weak interactions between the cation and the anion. Using counterpoise correction method to estimate the basis set superposition error, the interaction energy between the cation and anion is 346.78 kJ/mol.     

Quantum Chemistry Study on the Geometrical Structures of Small Centipedo－boranes

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β-环糊精与有机胺之间包合作用的理论与实验研究

通过实验和理论计算方法研究了β-环糊精(CD)与乙二胺1及它的三个类似物: 二乙烯三胺2、三乙胺3和乙二胺四乙酸4之间的包合作用. 利用旋光法确定了β-CD与客体分子形成1:1型主–客体包合物, 在298.2 K下测定了包合物在水中的稳定常数(K). 采用半经验PM3方法考察了β-CD与短链脂肪胺1~7、环状脂肪胺8~11以及芳香胺12~13的分子间结合能力, 报道了β-CD与这些客体分子间的包合络合过程并讨论了这些包合体系之间的包合差异性. 变形能和水合能对包合体系的相互作用能的贡献均相当小. β-CD包合物的稳定性取决于主、客体分子之间的尺寸匹配. 对于β-CD与客体1~4形成的包合物而言, 旋光法测定的包合物的K值的顺序与PM3计算得到的包合物络合能绝对值的排序有很好的一致性.     

环糊精对甲基麻黄碱手性识别的电喷雾质谱研究

利用质谱仪,使用电喷雾离子源,分别研究了以α-环糊精、β-环糊精和产环糊精作为手性拆分剂对手性药物甲基麻黄碱的手性识别效应．实验结果表明,3种环糊精对甲基麻黄碱对映体均有较强的手性识别效应,Rchiral分别为2．43、3．51、4．52．研究了电压的变化对α-环糊精、β-环糊精和γ-环糊精的手性识别的影响,研究发现,在不同的电压下,这3种环糊精对甲基麻黄碱均有手性识别能力．     

A comparative study by AM1, PM3 and ab initio HF/3-21G methods on the structure and reactivity of monosubstituted carbanion 1,2,4-triazolium ylides

A full conformational analysis of six 1,2,4-monosubstituted carbanion 1,2,4-triazolium ylides 4 a–f was performed using AM1, PM3 and HF/3-21G methods. The C-type conformers were found as the most stable structures by these different methods. This study also includes a qualitative estimation of the chemical behavior of triazolium ylides 4 a–f as nucleophilic agents on the level of ylide carbon atoms. The ab initio 3-21G method seems to be the most suitable in the characterization of these molecular systems.     

A Quantum Chemistry Study of Inhibition Properties of Imidazole and Its Derivatives on Iron Surface Corrosion

The geometries of imidazole and its derivatives were respectively optimized by using ab initio method, and the molecular orbital energy levels and the charge densities were obtained for their optimum geometries. The frontier orbital energy levels, and the net charges of N (1) atom and the imidazole ring of those molecules were obtained with ab initio and SCC-DV-Xα methods. It was found that the inhibition properties of those compounds change with the highest occupied molecular orbital energy levels, and the net charges of N (1) atom. We took four iron atoms on the crystal plane (100) of α-iron as the surface which was used to study the adsorption towards the inhibitors. The adsorption models of the inhibitor to be adsorbed on the Fe-cluster surface were optimized with SCC-DV-Xα method. It turns out that the most favorable model is that the inhibitor molecule is adsorbed on the Fe-cluster surface in an inclined state. The calculation shows that the stabilization energies of the systems are well correlated with the inhibition efficiencies.     

Binding of Cationic and Neutral Phenanthridine Intercalators to a DNA Oligomer Is Controlled by Dispersion Energy: Quantum Chemical Calculations and Molecular Mechanics Simulations

Correlated ab initio as well as semiempirical quantum chemical calculations and molecular dynamics simulations were used to study the intercalation of cationic ethidium, cationic 5‐ethyl‐6‐phenylphenanthridinium and uncharged 3,8‐diamino‐6‐phenylphenanthridine to DNA. The stabilization energy of the cationic intercalators is considerably larger than that of the uncharged one. The dominant energy contribution with all intercalators is represented by dispersion energy. In the case of the cationic intercalators, the electrostatic and charge‐transfer terms are also important. The ΔG of ethidium intercalation to DNA was estimated at ?4.5 kcal mol^?1 and this value agrees well with the experimental result. Of six contributions to the final free energy, the interaction energy value is crucial. The intercalation process is governed by the non‐covalent stacking (including charge‐transfer) interaction while the hydrogen bonding between the ethidium amino groups and the DNA backbone is less important. This is confirmed by the evaluation of the interaction energy as well as by the calculation of the free energy change. The intercalation affects the macroscopic properties of DNA in terms of its flexibility. This explains the easier entry of another intercalator molecule in the vicinity of an existing intercalation site.     

Molecular Recognition: Preparation of Polyrotaxan and Tubular Polymer from Cyclodextrin

We found that many α-CDs are threaded on a poly(ethylene glycol) (PEG) chain to form a crystalline complex in high yields, although β-CD did not form complexes with PEG. It was made clear that the relationship between the chain cross-sectional areas of the polymers and the diameters of the cavities of cyclodextrins is very important in the complex formation of polymers and cyclodextrins. Polyrotaxanes were prepared by the reaction of PEG–bisamine (PEGBA), which is PEG with amino groups in both ends, with 2,4-dinitro-1-fluorobenzene. In addition, the molecular tubes, a new family of novel nanostructures, were prepared and characterized. These findings indicate that such template synthesis provides a new approach to construct new nanostrutures, which may have implications for molecular technologies and materials science. © 1997 John Wiley & Sons, Ltd.     

Cyclodextrin Complexation of the Stilbene 4-(2-(4-Tert-butylphenyl)ethen-1-yl)- benzoate and the Self-assembly of Molecular Devices

E-4-(2-(4- tert - butylphenyl) ethen-1- yl)benzoate, E-1^–, photoisomerizes to the Z-1^– isomer and vice versa in the free state and in the binary complexes 2·E-1^–, 2·Z-1^–, 3·E-1^– and 3·Z-1^– where 2 is the urea-linked cyclodextrin N-(6 ^A -deoxy--cyclodextrin-6 ^A - yl)-N-(6 ^A -deoxy--cyclodextrin-6 ^A - yl)urea and 3 is N,N- bis(6 ^A -deoxy--cyclodextrin-6 ^A - yl)urea. In 2·E-1^–and 3·E-1^– the stilbene occupies both cyclodextrin (CD) components of 2 and 3, whereas in 2·Z-1^– and 3·Z-1^– it only occupies one CD component while the other CD component is unoccupied. 4- tert - Butylphenolate, 4^–, and its carboxylate, 5^–, and sulfonate, 6^–, analogues form the ternary complex 2·Z-1^–·4^– and its analogues and also 3·Z-1^–·4^– and its analogues. These photoisomerize to 2·E-1^–and 3·E-1^– and either free 4^–, 57^– or 6^– and thereby function as molecular devices.     

环糊精醛及其衍生物的合成与性能研究进展

综述了环糊精醛及其衍生物的合成、分子识别作用和模拟酶催化方面的最新研究进展.     

Quantum Chemical Study on Structure-activity Relationship of Several Kinds of Drugs

1 INTRODUCTION In recent years, with the development of mole- cular biology, biological chemistry, structural chemi- stry and computer chemistry, reasonable molecular design based on the structure of drug receptor has captured the interest of researchers. Molecular pro- perties of drugs are usually correlated with biolo- gical activities and this correlation study is known as quantitative structure-activity relationship (QSAR)[1～7]. QSAR studies have been extensively used to corre- la…     

环糊精包结物的制备与研究方法

环糊精是由6,7,8个葡萄糖基构成的环状化合物,分别叫做α,β,γ-CD。它们具有亲水的外围及疏水的内腔,可与多种物质形成包结物,而改变物质的特性,因而被广泛应用于各行各类,为了更好地研究环糊精包结物,在查阅大量文献的基础上,总结出环糊精包结物的多种制备方法及研究方法。     

亚烷基卡宾及取代亚烷基卡宾与环硫乙烷反应的量子化学研究

用量子化学的密度泛函理论(DFT)在6-311G(d, p)水平上对亚烷基卡宾及取代亚烷基卡宾与环硫乙烷的硫转移反应机理进行了系统的研究. 用IRC对过渡态进行了确认. 并用组态混合模型讨论了反应势垒(ΔE^≠)与XYC＝C的单-三态能量差ΔE_ST之间的关系. 结果表明, 取代基的电负性是控制反应的主要因素, 取代基的电负性越大, 取代基越多, π电子给予体越多, 单-三态能量差ΔE_ST就越小, 该反应的活化能就越小, 反应越容易发生. 同时还讨论了该反应中环硫乙烷的C—S键的解离过程. 并与标题化合物和环氧乙烷的氧转移反应进行了比较.     

尿素晶体介电性能的量子化学计算

利用量子化学的第一性原理,在自洽场理论水平上对尿素晶体的线性和非线性光学介电性质进行了定量计算,获得了与实验值相符的理论计算结果.提供了一种解决分子晶体量子化学理论计算的新思路.     

2,3-二氮杂二环-[2,2,2]-辛-2-烯与卤素分子间电荷转移相互作用的量子化学研究

对2,3-二氮杂二环-[2,2,2]-辛-2-烯 (DBO) 与Cl2、Br2和I2 3种卤素分子形成的s型电荷转移复合物进行了不同方法的理论计算。结果表明, MP2方法结合LanL2DZ*基组可以很好地描述DBO与卤素分子间的相互作用。其中, DBO与I2的结合能为33.6 kJ/mol, 与DBO…Br2的结合能接近, 明显大于DBO…Cl2相应的值。几何结构变化以及布居分析均与这一结果吻合。针对DBO的结构, 对DBO与I2间 形成p型电荷转移复合物以及DBO…(I2)2的可能性进行了理论分析和预测。