应用人工神经网络预测多氯代二苯骈呋喃的色谱保留指数

以量子化学方法在密度泛函B3LYP/6-31G(d)水平上计算得到了多氯代二苯骈呋喃系列化合物(PCDF)分子的结构参数:最高占据轨道能(EHOMO)、最低空轨道能(ELUMO)、最正原子净电荷(q+)、最负原子净电荷(q-)、分子偶极矩(μ)、极化率(α)、分子平均体积(Vm)、恒容热容(C■V).采用误差反向传播(BP)算法的人工神经网络,建立了EHOMO、ELUMO、q+、q-、μ、α、Vm、C■V与PCDF色谱保留指数之间关系的模型,检测样本的预报值与实验值相对误差范围为-1.66%².39%,平均相对误差为0.31%,达到了很好的预测效果.     

氯键酸度的量子化学参数表示

研究了137个化合物的总氯键酸度（∑α2^H)与最子化学参数的相关性，对于含羟基或羧基化合物，∑α2^H=-0.0277 3.826QH-0.0273ELUMO-0.0654EHOMO 3.085Qo(n=70,r=0.982)，其中QH表示羟基或羧基氢原子净电荷，ELUMO表示最低未占据分子轨道能级，EHOMO表示最高占据分子轨道能级，Qo表示羟基或羧基中与氢原子的氧原子净电荷；对于含氨基化合物，∑α2^H＝1.569 3.3637QH-0.1235EHOMO(n=49,r=0.985)，其中QH表示氨基中较正氢原子的净电荷；对于含亚氨基化合物，∑α2^H=0.0472 3.676QH(n=18,r=0.993),其中QH表示亚氨基氢原子的净电荷。     

氢化可的松和表氢化可的松的密度泛函理论研究

采用密度泛函理论B3LYP/6-31G和B3LYP/6-311G*方法优化了氢化可的松和表氢化可的松的几何结构,利用优化的结构得到了氢化可的松和表氢化可的松的原子净电荷、总能量及前沿分子轨道组成.基于简谐振动分析求得了氢化可的松和表氢化可的松的红外光谱频率和强度,由统计热力学分析得到了热力学函数;进而确定了氢化可的松和...     

氢化可的松的热力学函数和晶体结构——密度泛函理论分析

采用密度泛函理论B3LYP/6-31G和B3LYP/6-311G*方法优化了气相状态氢化可的松的几何结构,利用优化的结构得到了氢化可的松各原子净电荷及前沿轨道分布;基于简谐振动分析求得氢化可的松的红外光谱频率和热力学函数;并计算了环己烷、乙酸丁酯、二氯乙烷、异丙醇、甲醇、水六种不同极性的溶剂对氢化可的松几何构型、电荷分布及能量的影响.结果表明,由理论计算得到的氢化可的松的晶体结构与实测的晶体结构接近.     

非金属氢化物pKa定量结构性质关系(QSPR)研究

采用Tomasi的极化统一模型对非金属氢化物HmA在水相条件下进行从头算, 选取与A原子电子密度相关的7个量子化学参数对氢化物pKa进行多元回归和逐步回归, 建立的QSPR方程相关系数R分别为0.9984和0.9947, 标准偏差s分别为1.7349和2.3618, 留一法交叉验证的结果则为R=0.9689和0.9895, s=7.5985和3.3118, 表明由逐步回归建立的方程具有更高的预测可靠性, 同时也表明逐步回归分析引入的原子净电荷数NC、电荷布居数TP和最低未占分子轨道能级ELUMO 3个参数是影响HmA酸强度的关键参数. 对NC, TP和ELUMO的物理意义及其对HmA pKa影响的深入分析表明, 这3个参数是决定A原子电子密度大小的主要因素, ELUMO和TP则分别是同主族氢化物和同周期氢化物酸性强弱递变的决定因素.     

结合三维静电势参数研究化合物溶解度与溶剂分子结构间的定量关系

对一系列溶剂分子进行了结构优化和静电势及其导出参数的计算,运用多元线 性回归方法对10种化合物萘、菲、蒽、联苯、苊、六氯苯、苯偶酰、噻吨-9-酮、 二苯砜和敌草隆的溶解性能与溶剂分子的结构参数进行了关联。结果表明：分子表 面最正和最负的静电势V_(s,max)和V_(s,min)、电荷分离度Π以及分子的静电相互 作用趋势量τ这四个三维静电势参数,加上分子的前线轨道能级ε_(HOMO)和ε_ (LUMO)能很好地用于表达这些化合物在不同纯溶剂中的溶解度与溶剂分子结构间的 定量关系。     

13位取代苦参碱衍生物抗癌活性的定量构效关系研究

采用密度泛函理论B3LYP方法计算了13个13位取代苦参碱衍生物的电子结构,研究了化合物结构与抑制人肝癌细胞HepG2抗癌活性的定量构效关系(QSAR).结果表明:(1)13位取代的苦参碱类衍生物的最低空轨道能ELUMO越低,最低空轨道与最高占据轨道的能隙ΔE越小,化合物抗癌活性越高;(2)分子的能量Etotal、面积S以及体积V越大,其极化度P越大,活性越大;(3)分子的油水分配系数logP越大,活性越大,即分子的疏水性增大活性增强.综合得到了显著性较好的QSAR方程:-lgIC50=97.008-11.759ΔE+818.602QC2-2.132×10-4Etotal,可用于预测该类衍生物抑制人肝癌细胞HepG2的活性并进行分子设计.     

含B-N相互作用偶氮苯强荧光材料光电性质的理论研究

本文基于增大光谱发光强度的结构修饰方法,采用理论计算方法研究了结构修饰后分子的电子性质、光谱性质以及电荷传输性质的变化.计算结果表明,-N(CH3)2取代、-N(CH3)2和-Br组合取代有助于吸收/发射光谱发光强度的提高.与母体分子相比,-N(CH3)2和-Br取代位置不同或取代数量不同可以引起最高占据分子轨道能量(EHOMO)、最低空分子轨道能量(ELUMO)和能隙(Eg=ELUMO-EHOMO)发生明显变化,从而有效调节了最大吸收波长(λabs)和最大发射波长(λem),从理论角度设计了一系列蓝光和绿光材料.重组能计算显示,除了GM-1和GM-6,其余分子可以作为有机电致发光材料(OLEDs)中的空穴传输材料,GM-1和GM-7可以作为双极性电荷传输材料.     

新烟碱类杀虫剂生物活性的理论研究和结构修饰*

在B3LYP/6-311G基组水平下,运用密度泛函理论(DFT)的量子化学方法,对20种重氮乙烷新烟碱类杀虫剂分子的电子结构特征进行了研究,获得了它们的前线轨道能(EHOMO、ENHOMO、ELUMO、ENLUMO等)、原子电荷(Qi)、摩尔熵(Sm)、偶极矩(μ)等量化参数与物理性质。经最佳变量子集回归研究发现,重氮乙烷新烟碱类杀虫剂分子对果蝇n AChRs、哺乳动物α4β2亚型的亲和力常数(p KD、p KA)分别与ELUMO、QW、QF、QN等参数具有良好的线性关系。逐一或逐四剔除交互验证以及VIF、tα/2检验,所建2个QSAR模型具有良好的稳健性及预测能力。根据2个QSAR模型推断了重氮乙烷新烟碱类分子可能的杀虫机理。进一步研究发现,在重氮乙烷新烟碱类分子的吡啶环上的合适部位,选用不含复键的吸电子能力较强的取代基团对其进行结构修饰,有利于提高修饰后分子的生物活性。基于分子17,设计出4种经结构修饰后对果蝇n AChRs亲和力显著提高的重氮乙烷新烟碱类分子(分别是分子27,28,30和31),希望能得到实验的证实。     

流动条件下两种不同亲水基团咪唑啉型缓蚀剂的缓蚀性能

选择了两种含有不同亲水基团的咪唑啉型缓蚀剂, 即1-胺乙基-2-十一烷基咪唑啉(AEI-11)和1-羟乙基-2-十一烷基咪唑啉(HEI-11), 分别在静态及动态条件下,采用失重法、极化曲线法、电化学阻抗谱法研究了上述缓蚀剂对N80钢在CO2饱和的3%(w)NaCl溶液中的缓蚀性能. 研究结果表明, 无论在静态和动态条件下, HEI-11均表现出更佳的缓蚀性能, 即咪唑啉型缓蚀剂的缓蚀性能与亲水基团的极性成正比; 在流动条件为5 m·s-1时, 缓蚀剂的缓蚀效率显著降低. 为了进一步研究缓蚀剂的缓蚀性能与其结构的关系, 运用量子化学法计算了缓蚀剂的EHOMO(最高占有分子轨道)、ELUMO(最低空分子轨道), 结果表明缓蚀剂的缓蚀效率与EHOMO成正比, 与ELUMO及ELUMO与EHOMO的差值驻E成反比.     

Intramolecular energy transfer in 3-amino-N-(7′-methoxy-4′-methylcoumaryl)phthalimide

The synthesis and fluorescence property of 3-amino-N-(7′-methoxy-4′-methylcoumaryl)phthalimide (AMMP) are described. The fluorescence of AMMP originated during the intramolecular energy transfer from the coumarin moiety to the phthalimde moiety in various solvents. The ab initio quantum chemical calculation of the AMMP revealed that the HOMO and LUMO of AMMP were localized in the coumarin and phthalimide moieties, respectively.     

Synthesis of a Double Helicene by a Palladium‐Catalyzed Cross‐Coupling Reaction: Structure and Physical Properties

For this study, twisted π‐extended helicene 1 and double helicene 2 with a helicene framework were synthesized through palladium‐catalyzed C?H arylation or Suzuki–Miyaura coupling reaction. X‐ray crystallography revealed grossly twisted structures that were soluble in various conventional organic solvents. Optical properties based on UV/Vis and fluorescence spectra were measured. Electrochemical properties were also studied by measurements of cyclic voltammetry in 1 and 2 , which revealed their HOMO and the LUMO energies. Theoretical calculation supports their HOMO and LUMO energies and molecular orbitals. Furthermore, a racemization process of 2 predicted that the activation free energy at 300 K would be 31.8 kcal mol^?1 by DFT calculation, which indicated the static helicity at 300 K.     

Determination of band curvatures by angle-resolved two-photon photoemission in thin films of C60 on Ag(111)

The thickness-dependent interfacial band structure was determined for thin films of C(60) on Ag(111) by angle-resolved two-photon photoemission spectroscopy. Dispersions of molecular-orbital derived bands (HOMO, LUMO+1, and LUMO+2) were acquired, and limits were placed on their possible effective masses. A group theoretic approach is also incorporated to further understand the properties of these states. The HOMO, LUMO+1, and LUMO+2 bands possess (best-fit) effective masses of -7 m(e), -7 m(e), and -12 m(e), respectively. These values are consistent with theoretical calculations, averaged over the closely spaced subbands for each state, and provide practical limits on the effective fundamental charge-transport properties of C(60) films.     

Inverse isotope effects and electron-phonon coupling in the positively charged deutero- and fluoroacenes

Electron-phonon interactions in the monocations of deutero- and fluoroacenes are studied and compared with those in the monocations of acenes and those in the monoanions of fluoroacenes. Because of the significant phase pattern difference between the highest occupied molecular orbitals (HOMO) and the lowest unoccupied molecular orbitals (LUMO), the frequency modes lower than 500 cm(-1) and the high-frequency modes around 1400 cm(-1) couple more strongly to the LUMO than to the HOMO, while the frequency modes around 500 cm(-1) and the frequency modes around 1600 cm(-1) couple more strongly to the HOMO than to the LUMO in fluoroacenes with D2h geometry. The total electron-phonon coupling constants for the monocations (l(HOMO)) are estimated and compared with those for the monoanions (l(LUMO)) in deutero- and fluoroacenes. The l(HOMO) values are estimated to be 0.418, 0.399, 0.301, 0.255, and 0.222 eV for C6F6 (1f), C10F8 (2f), C14F10 (3f), C18F12 (4f), and C22F14 (5f), respectively. The l(HOMO) values are smaller than the l(LUMO) values in small fluoroacenes. But the l(HOMO) value decreases with an increase in molecular size less rapidly than the l(LUMO) value in fluoroacenes, and the l(HOMO) value of 0.074 eV is much larger than the l(LUMO) value of 0.009 eV in polyfluoroacene. The logarithmically averaged phonon frequencies for the monocations (omega(ln,HOMO)) are estimated to be larger than those for the monoanions (omega(ln,LUMO)) in fluoroacenes. This is because the C-C stretching modes around 1600 cm(-1) couple most strongly to the HOMO, and those around 1400 cm(-1) couple the most strongly to the LUMO in fluoroacenes. The significant phase pattern difference between the HOMO and the LUMO is the main reason for the calculational results. The l(HOMO) values increase much more significantly by H-F substitution than by H-D substitution in acenes. The possible inverse isotope effects in the electron-phonon interactions as a consequence of deuteration in the monocations of nanosized molecules are suggested.     

The kinetics and mechanism of cyclodimerization of alkylthiopropenals

The kinetics of 2-alkylthiopropenals cyclodimerization was studied in the temperature range from -7 to +42 °C in heptane and at 20 °C in various solvents. The rate constants for cyclodimerization of 2-alkylthiopropenals are four orders of magnitude higher than those for dimerization of the oxygen-containing analogs, 2-alkoxypropenals, and are independent of the solvent polarity and substituent steric constant. The activation parameters for 2-butylthiopropenal cyclodimerization were estimated. The distribution of electron density in the 2-methoxy- and 2-methylthiopropenals molecules was calculated by the ab initio method. From comparison of the HOMO and LUMO energies for these aldehydes it was concluded that the ratio between the cyclodimerization rates for 2-alkylthio-, 2-ethoxypropenals, and propenal is determined by the HOMO–LUMO gap.     

金属酞菁配合物的从头计算研究

利用从头计算方法研究了6种金属酞菁MPc(M=Zn2+、Cu2 +、Ni2+、Co2+、Fe2+、Mn2+)。得到了它们的基态能量,基态自旋多重度,分子轨道组成与能级,电荷分布与键序。其中,自旋多重度的计算结果与实验相符。中心离子d轨道参与HOMO、LUMO构成的程度可以解释各MPc光敏活性不同的实验现象。     

外电场下氮化铝分子结构和光谱研究

以6-311＋G(2DF)为基函数, 采用密度泛函B3P86的方法研究了外电场作用下氮化铝(AlN)基态分子的几何结构、HOMO能级、LUMO能级、能隙及谐振频率. 结果表明, 外电场的大小和方向对AlN分子基态的这些性质有明显影响. 在所加的电场范围内, 随着外电场的增大分子键长减小, 谐振频率增大, 总能量升高, 在F＝0.02 a.u.时能量达到最大, 为－297.4217 a.u., 此后继续增大电场强度, 系统总能量则开始降低; EH 和EL 随着电场的增加均逐渐增大, 在 F＝0.01 a.u.时, EH 和EL均取得最大值, 分别为－0.2776和－0.0828 a.u., 随着电场的继续增大, 能级EH和EL均逐渐减小, 而能隙在外电场增大的过程中始终处于减小趋势.     

定量结构-性质相关原理在阴离子表面活性剂临界胶束浓度预测中的应用

利用定量结构-性能相关（QSPR）原理，建立起了8类不同结构，计40个阴离子 表面活性剂临界胶束浓度（cmc）的定量模型。所得到的最佳模型包括：分子总能 量（E_T）、分子生成热（ΔH_f）、分子偶极矩（D）、前线分子轨道能量（E_ (LUMO),E_(HOMO)）及憎水基0级Kier & Hall指数（KHO），计6个描述符，复相关 系数R~2 = 0.9778。