河豚毒素(TTX)及其衍生物的电子结构和构效关系及与石房蛤毒素(STX)的比较研究

对河豚毒素(TTX)及其五个衍生物进行了量子化学计算, 根据对其电子结构及相关分析研究结果, 结合其空间结构特点, 讨论了它们的活性部位、作用方式及构效关系, 发现胍基是最重要的正电中心,在与受体作用时发挥接受电子的重要作用; O(17), O(18), O(15),O(21), O(19)等氧原子是供电子的主要负电部位。对TTX与石房蛤毒素(STX)进行了电子结构和空间结构比较, 发现它们具有相似的电子结构特征, 而且主要活性部位在空间位置上基本相互对应。这表明钠离子通道阻断剂在与受体相互作用时具有共同的结构特征和作用方式, 同时也为探讨受体结构提供了有价值的信息。     

河豚毒素(TTX)及其衍生物的电子结构和构效关系及与石房蛤毒素(STX)的比较研究

对河豚毒素(TTX)及其五个衍生物进行了量子化学计算, 根据对其电子结构及相关分析研究结果, 结合其空间结构特点, 讨论了它们的活性部位、作用方式及构效关系, 发现胍基是最重要的正电中心,在与受体作用时发挥接受电子的重要作用; O(17), O(18), O(15),O(21), O(19)等氧原子是供电子的主要负电部位。对TTX与石房蛤毒素(STX)进行了电子结构和空间结构比较, 发现它们具有相似的电子结构特征, 而且主要活性部位在空间位置上基本相互对应。这表明钠离子通道阻断剂在与受体相互作用时具有共同的结构特征和作用方式, 同时也为探讨受体结构提供了有价值的信息。     

噻吩基卟啉衍生物的单光子和双光子吸收性质的理论研究

本文理论上研究了两个系列的噻吩基卟啉衍生物,这种衍生物在可见光区具有大的双光子吸收截面。用密度泛函理论和ZINDO-SOS方法,计算了分子的几何构型、电子结构,单光子和双光子吸收性质。结果显示噻吩单元的数目影响分子的单光子和双光子吸收性质。具有两个或三个噻吩基团的噻吩基卟啉衍生物在较大范围内具有可用于实际应用中的双光子吸收响应,这一性质有利于这类分子在光限幅中的应用。插入乙炔基有利于扩大共轭范围,增加分子的双光子吸收截面。同时,乙炔基团的加入导致了单光子和双光子波长的红移。从高透明性和相对大的非线性光学响应考虑,噻吩基卟啉衍生物是一类有应用前景的双光子吸收材料。     

CH3和CN取代8-羟基喹啉电子光谱性质的含时密度泛函理论研究

对8－羟基喹啉QH及其代衍生物MQH和CNQH用密度泛函方法（DFT）在B3LYP／6－31G＊水平上进行理论计算，探讨了供电子取代基（－CH3）和吸电子取代基（－CN）对分子电子结构，前线分子轨道能和光谱性质等的影响规律，在此基础上采用含时密度泛涵方法（TD－DFT）计算了电子光谱，计算结果表明，MQH，QH和CNQH的最低激发单重态都是A，激发能分别为3．58，3．72和3．74eV，在高激发态，无论是供电子基团（－CH3）还是拉电子基团（－CN），都导致取代衍生物的电子光谱红移。     

C(4)取代紫杉醇类似物的定量构效关系研究

用量子化学B3LYP／6-31G方法计算了23个C（4）取代紫杉醇类似物的结构,用遗传算法（GFA）对能量、电性、拓扑及热力学等类型的278个结构描述符进行筛选,并回归建立其抑制人体结肠癌细胞HCT-116活性的定量构效关系（QSAR）．QSAR方程含分子体积Vm、分子分支度指数CHI-O、分子中带正电荷原子的溶剂可积面积与其所带电荷之积的加和值Jurs-PPSA-3以及分子表面积S4个结构描述符．方程的拟合相关系数的平方R^0及交叉验证系数Q^2分别为0．956和0．913,所得QSAR具有可信的预报能力．由优化后的几何构型知,C（4）取代基、C（13）侧链和2-OBz三基团共同形成疏水腔,C（4）取代基的改变影响C（13）侧链的电子结构．C（13）连接的18号O原子的负电荷越大、3’位连接的NHBz基团的极性越小活性越高;C（4）取代基若为吸电子基对活性不利;适当增大分子体积、表面积和疏水性,保持一定的分支度对活性有利．     

D-π-A-π-D型萘基衍生物的电子、光谱和电荷传输性质

采用量子化学方法研究了给体-π桥-受体-π桥-给体(D-π-A-π-D)型萘基衍生物及其“CH”/N 杂原子取代衍生物的电子、光谱和电荷传输性质. 计算结果表明, 分子结构的变化引起了电子结构和能隙的变化, 进而改变了吸收和发射光谱. 其中, 衍生物的最大发射波长几乎覆盖了可见光区域(447.7-743.1 nm). 而且, 光谱的Stokes 位移较大(106.1-222.4 nm), 产生的原因在于, 与基态结构相比较, 衍生物的激发态结构中分子主干存在两个相连部分更为平面的构型. 计算结果还显示, 所有衍生物都可以作为有机电致发光二极管中的空穴传输材料.     

四苯基卟啉质子化结构变化的理论研究

用半经验的ＡＭＩ ＭＯ方法,进行合理的对称性限制,计算了一类重要的卟啉衍生物──四苯基卟啉（ＴＰＰＨ_２）及其质子化二酸（ＴＰＰＨ_4~2 ）的构型,并通过结构分析,电荷布居分析和前线轨道分析,讨论了质子化过程中的构型变化以及这种变化对分子堆积可能带来的影响。     

Theoretical Study on Excited-State Intramolecular Proton Transfer of 2-（2＇-Aminophenyl）benzimidazole Derivatives： Substituent EffectE-C=O or E-OSi. The K＊ configuration become more stable than E＊ in S~ state when substitutent is E-CC, E-NH, E-CO, E-...

研究了2-（2’-氨基苯基）苯并咪唑（APBI）氨基中一个H被CH3（E-C）,Sill3（E-OSi）,NH2（E-N）,COH（E-CO）,N02（E-N02）,CF3（E-F）,CN（E-CN3）,OMe（E-OMe）,COCH3（E-CC）,Ts（E-S）,P-CH3C6H4CO（E-C=0）和P-CH3C6H4NHCO（E-NH）取代后,其基态及激发态分子内质子转移（ESIPT）性质的变化规律．结果表明各衍生物基态最稳定构型为烯醇式构型E,次稳定构型旋转异构体R,酮式构型K只有当取代基为E-CN3,E-F,E-N02,E-N,E-OMe和E-S时才存在．基态各环的核独立化学位移（NICS）研究表明取代基的引入会影响APBI环电子离域性．所有APBI衍生物都能发生激发态分子内质子转移,当引入取代基为E-CN3,E-N或E-OMe时,所得的APBI衍生物S1态分子内质子转移是无能垒过程;引入取代基为E．c,E．C=O或E．OSi时,对APBI的ESIPT势能面基本无影响,而当取代基为E-CC,E-NH,E-CO,E-F,E-N02和E-S时,使得Sl态APBI的K’构型能量低于E     

C60-TTF及其衍生物的结构与光谱的理论研究

采用ZINDO系列方法优化了环状桥联的C60－TTF分子及其7个衍生物的几何构型，研究了各分子的电子结构，以稳定构型为基础，计算了各分子的电子光谱，理论计算值与实验值符合得较好，对电子光 的本质在理论上进行了指认，部分合物的电子光谱属于理论预测。     

噻吩多烯基丙二酸二甲酯类化合物的气相研究

气相Hel紫外光电子能谱（UPS）能从孤立分子的分子轨道特性给出研究分子的电子结构、构型、构象以及成键特性等的大量信息．为此，我们开展了分子体系中带有数基为阻断基团的三岔共把系列化合物的＊PS研究【’－‘］其各自分子轨道的特性提供了它们遵守同东线性规律的实验和理论依据．本文报导唾吩多烯基雨二酸二甲酯类化合物（1）、（2）、（3）的UPS研究·结果表明，它们遵从同系线性规律；同时从分子轨道的原子特性论证了文献间推证的一C00CH3基团的结构效应．这些尚未见文献报导．1实验和计算文献则报导了这类化合物的合成·研究化…     

腺苷酸琥珀酸合成酶与其抑制剂的分子机制研究

利用密度泛函B3LYP方法选择6-31G(d)基组对腺苷酸琥珀酸合成酶(AdSS)天然抑制剂及其衍生物的结构进行优化,并对其稳定性进行了分析,同时采用Mulliken键序、原子电荷分布、表观静电势等对AdSS抑制剂及其衍生物电子结构与其生物活性相关性进行了理论研究.基于腺苷酸琥珀酸合成酶(AdSS)与其底物肌苷单磷酸(IMP)复合物的晶体结构以及获得的天然抑制剂衍生物稳定构象,利用分子对接、分子力学优化及常温分子动力学模拟对AdSS酶与天然抑制剂及其衍生物的相互作用复合物结构进行理论预测.结果表明,AdSS酶的系列抑制剂中磷酸根基团和乙内酰脲(Hydantoin)官能团构成药效团模型,识别过程中范德华相互作用能的贡献大于静电相互作用能.     

石房蛤毒素(STX)衍生物的电子结构与毒性-结构关系研究

本文对十个石房蛤毒素(Saxitoxin,STX)衍生物进行了量子化学(INDO)计算,得到了多种电子结构信息。据此研究了它们的电子结构特征,确定了它们的活性部位。通过构效关系研究,发现某些电子结构指数与毒性之间存在较好的相关关系。这些结果为讨论该类化合物的作用机理、与受体之间的相互作用及进一步的分子设计提供了有价值的信息。     

Analytical calculation of atomic and molecular electrostatic potentials from the Poisson equation

An analytic formulation is given for the total potential in atomic and molecular systems, based on the electrostatic approach from the Hellmann-Feynman theorem. The potential function is obtained from the analytic solution of the Poisson equation using charge densities expressed as a superposition of gaussian functions. The method is independent of the specific LCAO approximation used for the calculation of the charge distribution function. The calculation of the potential and its derivatives to a rapid algorithm form, which can be used for the evaluation of various electronic properties and the treatment of experimental situation, even for large molecular systems.     

A computational analysis of the electrostatic potentials and relative bond strengths of hydrazine and some of its 1,1-dimethyl derivatives

We have carried out a computational study of hydrazine and five of its 1,1-dimethyl derivatives, focusing on their electrostatic potentials and relative bond strengths. Our approach has involved the calculation of ab initio self-consistent-field molecular orbital wave functions and molecular properties using the GAUSSIAN 82 system of programs. The electrostatic potentials of the hydrazines possess negative regions of varying sizes and strengths associated with the nitrogens of the α-diamino linkages. Through an analysis of the positions of the most negative potentials of these regions, we have obtained directly the dihedral angles between the nitrogen lone pairs in these systems. Our use of the electrostatic potential to obtain these angles is a direct and general approach, in contrast to indirect procedures used in the past. We find this dihedral angle to be close to 90° in hydrazine, with variations in the substituted hydrazines that depend on the nature of the substituents. A highly polar structure is found for 1-chloromethyl-1-methylhydrazine, which involves a delocalization of electronic charge from the substituted nitrogen towards the CH₂Cl group. We find that substituents able to withdraw significant amounts of electronic density from the central nitrogen lone pair regions, either through resonance or by induction, have a slight bond strengthening effect on the central N-N bond. This is attributed to a decrease in the repulsion between the weakened nitrogen lone pair regions. The difficulties encountered in seeking the controlled oxidation of hydrazine to nitro derivatives may be due, in part, to the fact that two factors which would favor this, highly negative nitrogen potentials and strong N-N bonds, are opposing in nature.     

基于密度泛函理论研究碱性水溶液中乙内酰脲及其衍生物的结构及性质

乙内酰脲及其衍生物对多种金属离子具有良好的络合效果,是一种有望取代氰化物的绿色电镀络合剂。本文以密度泛函理论(DFT)方法对乙内酰脲及其衍生物的反应活性进行了研究。通过分子极性指数和极性表面积所占总面积百分比研究多种乙内酰脲衍生物在水中的溶解性,理论计算结果与文献报道的实验结果基本一致。通过原子电荷、表面静电势、原子对最高占据分子轨道的贡献、平均局部离子化能和简缩局部软度考察去质子化后的各原子的配位能力,其中含S原子的2-硫代乙内酰脲(TH)比其他衍生物具有更强的配位能力,其可能是有研究前景的无氰络合剂。通过解离常数预测各衍生物达到去质子化状态的难易程度。AIM拓扑分析表明所研究的分子结构稳定性较好,而在373K下的分子动力学模拟表明,1,3-二羟甲基-5,5-二甲基乙内酰脲(DMDMH)热稳定性较差,其他分子热稳定性较好。     

A new method to determine electrostatic potential around a macromolecule in solution from molecular wave functions

The three-dimensional reference interaction site model integral equation theory (3D-RISM) combined with the ab initio molecular orbital method (3D-RISM-SCF) is applied to a solvated macromolecular system. The solvation structure around a solute molecule is obtained from the 3D-RISM integral equation under the electrostatic potential of the solute molecule, calculated by the ab initio molecular orbital theory. The electrostatic potential should be calculated on each grid point in the three-dimensional real space. Therefore, the calculation of the electrostatic potential is the most time consuming part in this method. In this article, we propose a new procedure to save the computational cost for calculating the electrostatic potential and the solvated fock matrix. The strategy of this procedure is to evaluate the electrostatic potential and the solvated fock matrix in different ways, depending on the distance between solute and solvent. Inside the repulsive cores of solute atoms, it is possible to avoid the calculation of electrostatic potential and solvated Fock matrix by assuming the potential to be infinity. In the region sufficiently far from solute, they are evaluated classically by putting the effective point charge on each atom. In the intermediate region, the electrostatic potential is evaluated directly by integrating the molecular orbitals of the solute molecule. The electronic structure and the energy gradient of Methionine-Enkephalin and solvation structure are estimated by using this procedure in aqueous solution, and are compared with the results from other procedures. The results are compared also with those from the continuum model.     

Exploring the conformation,charge density distribution and the electrostatic properties of galanthamine molecule in the active site of AChE using DFT and AIM theory

Quantum chemical calculations and charge density analysis were carried out to understand the geometry, charge density distribution and the electrostatic properties of isolated galanthamine molecule (form I) and for the same lifted out from the active site (form II) of AChE. The optimized geometry of isolated galanthamine was obtained from a hybrid density functional theory (B3LYP/6‐311G**) calculation. A docking analysis on galanthamine with AChE was performed, and the lowest docked energy structure was selected from the active site of AChE for the further study. A single point energy quantum chemical calculation (B3LYP/6‐311G**) was carried out for the lowest energy structure, which was lifted from the galanthamine–AChE complex from molecular docking analysis. The structural comparison between (I) and (II) helps to understand the conformational modification of the galanthamine molecule in the active site. When the molecule present in the active site, the molecular geometry is seen to be significantly altered, specifically, large changes were observed in the outer core of the molecule while the inner core geometry is intact. The bond topological and electrostatic properties of (I) and (II) were calculated. The dipole moment of the galanthamine molecule also increases from 2.09 to 2.67 D in the process. A large negative electrostatic potential region is found at the vicinity of oxygen and nitrogen atoms of the molecule, which predominantly involve strong hydrophobic and electrostatic interactions with the amino acid residues TRP84, PHE330, GLY118, TYR70, and SER122 present in the active site of AChE. © 2013 Wiley Periodicals, Inc.     

The structure of geminal imidazolium bis(trifluoromethylsulfonyl)amide ionic liquids: a theoretical study of the gas phase ionic complexes

In this work we report molecular mechanics and ab initio calculations on the geminal di-imidazolium bis(trifluoromethylsulfonyl)amide ionic liquid in the gas phase. We report the likely energetically preferred geometries of the ionic complex and its main features in terms of charge distribution, electronic density, structure, and energetics. We find that the gas phase structure of the ionic complex is quite compact and that the alkyl chain connecting the two imidazolium charged rings is strongly bent in order to maximize their electrostatic interactions with the two anions.