精甲霜灵的电子结构及圆二色谱性质

采用量子化学密度泛函理论在B3LYP/6-311++G**水平上对精甲霜灵分子几何构型进行优化;在优化的基础上进行圆二色谱究。计算结果表明:(1)C(8)=O(9)与N(1)、C(3)=O(4)与O(5)之间均存在p—π共轭,N原子上另外2个取代基分别位于苯环上下方为最稳定构型。(2)VCD谱中,C(10)—H沿C(8)—C(10)—O(11)平面的摇摆振动在1020cm-1处存在正性康登效应;垂直于该平面的摇摆振动在1273cm-1处出现负性康登效应。C(2)原子上的C—H摇摆振动在的1334cm-1处存在强的康登效应。C(3)=O(4)在的1788cm-1处出现较强的吸收峰;C(8)=O(9)由于与手性中心的间隔一个N原子,其在VCD谱中未出现康登效应。(3)甲醇溶液中的理论ECD谱,228nm处存在正性康登效应,与实验值符合较好;同时,理论计算还预测标题化合物在201nm处存在负性康登效应。     

L-Thr-TPPMg电子结构及光谱性质的理论研究

采用密度泛函理论方法在B3LYP和混合基组(C、H原子采用6-31G(d);Mg、N、O采用6-311++G(2d,p))水平对含L-苏氨酸侧链的四苯基卟啉镁衍生物L-Thr-TPPMg的基态几何构型进行了优化,获得了稳定的分子构型。以获得的稳定构型为基础,在相同基组水平进行了红外吸收光谱研究;采用含时密度泛函理论方法,在相同基组水平进行了紫外吸收光谱和电子圆二色谱研究。理论研究发现:(1)L-苏氨酸的羧基氧原子与镁原子之间存在配位作用。(2)氮镁配位键、氧镁配位键的伸缩振动在IR谱中的1022 cm~(-1)、278 cm~(1)处呈现特征吸收峰。(3)理论UV谱存在Soret带和Q带吸收。Q带吸收峰主要由HOMO→LUMO的荷移跃迁贡献;Sorer带的吸收峰主要由HOMO-1→LUMO的荷移跃迁贡献。(4)Sorct区表现出分裂的ECD谱。第1 Cotton效应主要来源于分子由HOMO-1→LUMO的荷移跃迁;第2 Cotton效应主要由HOMO-1→LUMO+1的荷移跃迁贡献。上述跃迁均为π→π~*的荷移跃迁。     

五味子丙素立体异构体ECD谱的理论研究

采用密度泛函理论(DFT)方法和极化连续介质模型(PCM),在B3LYP/6-311++G**水平上对五味子丙素的一个立体异构体的基态几何构型进行了优化;以优化得到的稳定构型为基础,采用含时密度泛函理论(TD-DFT)方法,在相同基组水平进行了电子圆二色谱(ECD)研究,根据计算获得的电子跃迁吸收波长(λ)和电子旋转强度(R)拟合得到了理论ECD谱。理论研究发现:甲醇溶液中,2个苯环之间扭曲形成的二面角∠C(2)-C(1)-C(8)-C(7)约为64°;计算获得的理论ECD谱吸收峰略红移,各谱带形状与实验谱吻合较好。通过对相关跃迁性质的分析发现,理论ECD谱的吸收峰1主要由自于HOMO-2→LUMO和HOMO-2→LUMO+1的电子跃迁贡献;吸收峰2的吸收主要由HOMO→LUMO的电子跃迁贡献。这些结论对深入理解五味子丙素异构体的电子结构和手征光学性质具有一定的科学意义。     

麻黄碱及其立体异构体ECD谱的理论研究

采用Gaussian 03、SpecDis v1.58、Multiwfn 2.2.1、Molekel 5.4等软件对麻黄碱及其立体异构体的电子结构及电子圆二色谱(ECD谱)性质进行研究。计算结果表明:(1)电子密度拓扑分析证实麻黄碱及其立体异构体分子的H(7)与N(4)之间存在键鞍点,从该键鞍点出发存在连接H(7)、N(4)的键径,表明形成了分子内氢键。(2)研究获得了理论ECD谱。A1的ECD谱在(184、199、229)nm附近存在正性CD谱带;在188 nm、215 nm附近存在负性CD谱带。B1的ECD谱在184nm附近存在正性CD谱带,在187m附近存在负性CD谱带。C1的ECD谱在185nm、222nm附近存在正性CD谱带,在(192、199、234)nm附近存在负性CD谱带。D1的ECD谱中在186 nm、228 nm附近存在正性CD谱带,在195nm附近存在负性CD谱带。以上吸收特征可为麻黄碱及其立体异构体绝对构型鉴定提供参考信息。(3)分子轨道成份分析发现,A1、C1分子HOLO轨道主要分布在N(4)原子上,而LUMO轨道主要分布在苯环上。A1、C1理论ECD谱中,峰5的吸收带主要来源于HOMO→LUMO的电子跃迁,即主要由N(4)到苯环的n→π~*荷移跃迁引起。     

尾式L-苏氨酸卟啉亚铁ECD谱的理论解析

采用Gaussian 09软件,利用密度泛函理论和含时密度泛函理论方法,在B3LYP方法和混合基组(Fe(Ⅱ)采用赝式基组Lan2dz;N、O采用6-311++G(2d,p);C、H原子采用6-31G(d))水平对尾式L-苏氨酸卟啉亚铁的ECD谱进行了理论研究。采用Multiwfn和SpecDis程序对Gaussian 09软件的研究结果进一步分析,获得了分子轨道的组成成份,拟合得到了理论ECD谱。研究发现:(1)尾式L-苏氨酸卟啉亚铁在Soret区存在2个CD吸收带,在长波处为正的Cotton效应,在短波处为负的Cotton效应;(2)499 nm附近的CD吸收带(正)主要是由亚铁离子到卟吩环的荷移跃迁d_(FE(Ⅱ))→π_(porphin)~*引起的;(3)449 nm附近的CD吸收带(负)是由卟吩环到亚铁离子和羧基的π_(porphin)→d_(FE(Ⅱ))和π_(porphin)→π_(-COOH)~*荷移跃迁引起的。这些结论对深入理解配合物的手征光学性质具有一定的科学意义。     

丁酮烯醇钠分子结构性质及合成的理论研究

丁酮烯醇钠是合成4,4-二甲氧基-2-丁酮的中问体.本文采用密度泛函方法(DFT)在B3LYP/6-31G水平上给该化合物分子的几何构型全优化计算和振动分析,并在同一计算水平上采用scRF(PCM)模型比较合成标题化合物过程中的主副反应.结果表明:丁酮烯醇钠接受电子的能力较强,化学反应活性较高,但在甲醇中溶剂化效应减弱了羰基上碳原子的亲电性.气相计算的红外光谱与实验结果基本吻合.根据理论计算推测影响合成反应的主要因素与实验结果一致.     

二硝基吡唑并吡唑性能的量子化学研究

用B3LYP法,在6-31G(d,p)基组水平上计算二硝基吡唑并吡唑(DNPP)的性能,得其稳定的几何构型、分子轨道及键级;在振动分析的基础上求得体系的振动频率、IR谱及不同温度下的热力学性质,并得温度对热力学性能影响的关系式;用Monte-Carlo方法从理论上计算密度,运用Kamlet公式预测爆速。     

盐酸克伦特罗的密度泛函理论研究

应用密度泛函理论(DFT)的B3LYP方法,在6-31g(d)基组水平上对盐酸克伦特罗分子的结构特点和红外光谱进行了研究。研究发现,按照形成光谱的分子振动模式的不同,可将盐酸克伦特罗分子的红外振动光谱划分为(0~400)cm~(-1)、(400~1240)cm~(-1)、(1240~2300)cm~(-1)和(2300~4000)cm~(-1)四个区域,与其它区域中谱线的强度相比,(1240~2300)cm~(-1)区域的谱峰较强。此外,光谱中出现的谱线的数量要远小于简正振动的数目,分析认为这主要是由部分振动模式没有引起分子偶极矩的变化和存在简并现象等原因造成的。最后还对谱峰位置进行了指认。     

基于GA-PLS算法的小麦粉灰分含量快速检测

为得到噪声小、准确性强、自适应性良好的模型,对实验所得的近红外光谱进行预处理及优化波长是十分必要的.实验确定小麦粉中灰分含量为研究对象,提出将光谱预处理及遗传算法(GA)优化波长用于提高偏最小二乘法(PLS)定量建模的稳健性.对比在不同预处理方法下相关系数R2、矫正标准差(RMSEC)、预测标准偏差(RMSEP)3个指标,随机选择130份样本,建立预处理+GA+PLS定量分析模型.实验结果为:R2从70.31%提到了97.46%,RMSEC从0.0775降低到了0.0226,RMSEP从0.0996降低到了0.0213,表明基于光谱预处理结合GA优化谱区定量分析小麦粉中灰分含量可行,模型预测能力和精度更高.     

苏丹红I号的太赫兹光谱研究

采用太赫兹时域光谱(THz-TDS)技术测量了苏丹红Ⅰ号在0.5～2.0THz波段的光谱特性,得到了样品在室温氮气环境下的吸收谱和折射率谱,同时利用密度泛函理论计算了该分子在0.5～2.0THz的振动吸收谱.研究发现,苏丹红Ⅰ号在该波段范围存在THz光谱响应,且实验谱和计算谱之间能较好地进行相互印证,说明THz-TDS技术可以用来探测该样品分子的结构和振动情况.本文还给出了与光谱特征吸收对应的分子振动模型,用以认识分子对THz波的响应机制.该研究结果为将THz-TDS技术应用于食品质量安全检测提供了依据.     

吡嗪类硝基衍生物结构与爆轰性能的DFT研究

采用B3LYP/6-311++G**方法对26种硝基吡嗪类衍生物体系进行了全优化,几何优化结果表明所有优化后的化合物结构均无虚频,为势能面上的稳定结构;采用Monte-Carlo方法理论估算了26种化合物的密度,随着硝基数目的增加,密度增加;并设计等键等电子反应计算了其生成焓及其热力学性质,硝基数目逐渐增加时,Cp、S...     

1,3二(吡啶-2-基)苯及其衍生物的铂配合物的DFT研究

采用DFT B3LYP方法,在Lan12dz基组水平上对4种1,3-二(吡啶-2-基)苯及其衍生物的铂配合物分子结构进行全优化,然后用TD-DFT(B3LYP/Lan12dz)计算其吸收光谱.结果表明:计算得到的1,3二吡啶苯及其衍生物的铂配合物的儿何结构参数和吸收光谱与实验值相当接近,该方法可以准确预测此类化合物的电子光谱.该类化合物的电子跃迁都具有MM(X)L'LCT的特征,通过改变配体可以有效调节电子跃迁能级.     

Modeling of multifunctional donor-bridge-acceptor 4,6-di(thiophen-2-yl)pyrimidine derivatives: A first principles study

We have modeled multifunctional compounds by pi-elongation and push–pull strategy from the 4,6-di(thiophen-2-yl)pyrimidine. The ground state geometries have been optimized by density functional theory while excited state geometries were optimized by time dependent density functional theory (TDDFT). Structure–property relationship, electronic, optical and charge transfer properties (ionization potential, electron affinity and reorganization energies) were computed and discussed. By TDDFT absorption and emission have been calculated. The computed parameters were compared with available experimental data. The long-range corrected functional (LC-BLYP) is overestimating the highest occupied and lowest unoccupied molecular orbital energies, energy gaps while underestimating the absorption and fluorescence wavelengths. The B3LYP is good to reproduce the experimental data. The intra-molecular charge transfer has been observed from highest occupied molecular orbitals to lowest unoccupied molecular orbitals. The strong electron withdrawing and electron donor groups efficiently reduce the energy gaps. The decrease injection barrier and smaller reorganization energies are revealing that our designed derivatives would be efficient hole as well as electron transfer materials. These derivatives would be good light emitters e.g. blue, green, orange, red and near IR. The predicted values showed that the designed derivatives would be efficient for the organic field effect transistors, photovoltaics and light emitters.     

白芷香豆素分子电子结构及光谱性质的理论研究

采用量子化学密度泛函理论在B3LYP/6-31+G**水平上对白芷中的5种香豆素类化合物分子几何构型进行全优化:用含时密度泛函理论在相同水平对上述化合物分子进行电子吸收光谱研究.为模拟真实条件,采用PCM模型,以甲醇为溶剂,计算其对分子电子结构和光谱性质的影响.计算结果表明:标题化合物分子母环发生共轭形成大π键,为刚性...     

芳基咪唑啉类化合物胰岛素分泌生物活性的QSAR研究

采用密度泛函理论(DFT)的B3LYP/6-311G+(d,p)方法,对芳基咪唑啉类化合物的几何构型进行全优化,将一系列量子化学参数用于结构与胰岛素分泌生物活性的定量研究中。利用SPSS16.0软件进行相关性分析,结果表明,分子的偶极矩,分子的总能量,碳原子C(2)、C(3)、C(9)上的Mulliken电荷,以及N1-C2、C2-C3的键长均对其生物活性Log(Ins)有明显影响。本文最终选取2个最为相关的量子化学参数,偶极矩μ和C(3)原子上Mulliken电荷Q_3,建立了满意的QSAR模型(Log(Ins)=0.894+0.067μ+0.297 Q_3,N=12,R~2=0.856)。     

DFT study on the structures and properties of 3-nitro-1,2,4-triazol-5-one crystals at high pressure

The geometries, lattice parameters, electronic structures, XRD spectra and optical properties of the 3-nitro-1,2,4-triazol-5-one (NTO) crystals at high pressure (2, 4, 6, 8 and 10GPa) have been studied using density functional theory within the generalized gradient approximation implemented using ultrasoft pseudo-potentials. The computational results show that with increasing pressure, the NTO lattice parameters and hydrogen bonds lengths rapidly decrease and the geometries change very little. The total energy increases by approximately 27.543eV from 0 to 10GPa. NTO becomes increasingly conductive or metallic with increasing pressure, while the XRD peaks are shifted to greater angles and the absorption coefficient alpha(omega) increases.     

The effect of different π-bridge configuration on bi-anchored triphenylamine and phenyl modified triphenylamine based dyes for dye sensitized solar cell (DSSC) application: A theoretical approach

Twenty eight bi-anchored triphenylamine (TH-1 to TH-14) and phenyl modified triphenylamine (PH-TH-1 to PH-TH-14) based metal free organic dyes are designed for DSSC application. The electronic effect of different π-bridge configurations in donor-π-bridge-acceptor (D-π-A)₂ structure was theoretically simulated and verified using density functional theory (DFT) and time dependent density functional theory (TD-DFT). The triphenylamine and phenyl modified triphenylamine groups are used as donor and cyanoacrylic acid group is used as acceptor. Thiophene and cyanovinyl groups are used as π-bridge. The ground state molecular structure was optimized by density functional theory and the electronic absorption spectra were calculated by time dependent density functional theory. The light harvesting efficiency (LHE), dye regeneration energy (ΔG_reg) and electron injection energy (ΔG_inject) are determined by computational examination. It is observed that, when the number of π-bridge increases, the band gap of the dye decreases. Also the absorption maximum and molar extinction coefficient of the dyes are increased. Theoretical result shows that the thiophene-cyanovinyl and thiophene-thiophene-cyanovinyl–cyanovinyl configurations give broader and red shifted absorption spectrum compared to other configurations. Also the results of phenyl modified triphenylamine (PH-TH) dyes clearly show better absorption and dye regeneration energy compared to TH dyes.     

亚硝酰氢与羟基自由基反应的密度泛函理论研究

用密度泛函理论研究了HNO OH反应机理。在(U)B3LYP/aug-cc-pVTZ水平上,优化了反应通道上各驻点(反应物、中间体、过渡态和产物)的几何构型,获得了零点能校正后的反应势能曲线。研究表明:根据进攻方式的不同,有3个反应通道,反应通道不同则产物不同。反应的主要产物是NO H_2O,次要产物是NH_2 O_2;主要产物和次要产物与反应物的总能量之差(经零点能校正后)分别为-133.42 kJ/mol和150.44 kJ/mol。生成主要产物时主要反应通道的活化能为102.11 kJ/mol。     

CHARMM force field parameters for 2′-hydroxybiphenyl-2-sulfinate, 2-hydroxybiphenyl,and related analogs

2′-Hydroxybiphenyl-2-sulfinate (HBPS) desulfinase (DszB) catalyzes the cleavage of the carbon-sulfur bond from HBPS in the final step of microbial 4S pathway desulfurization reactions. DszB is notable for its substrate specificity and exhibits product inhibition, both of which hinder the overall 4S pathway turnover rate. To understand the molecular-level contributions to substrate and inhibitor binding to DszB, we plan to perform molecular dynamic simulations bound to an array of naphthenic molecules and biphenyl analogues of HBPS. However, many of the small molecules we are interested in are not included in standard force field packages, and thus, we must first produce accurate molecular mechanics force fields. Here, we develop and validate CHARMM-compatible force field parameters for the HBPS substrate, the 2-hydroxybiphenyl product, and potential inhibitors including: 2,2′-biphenol, 2-biphenyl carboxylic acid, 1,8-naphthosultam, and 1,8-naphthosultone. The selected molecules represent biphenyl compounds having both a single and double functional group and the planar naphthenic molecule class, all likely present in the oil-rich environment surrounding DszB-producing microorganisms. The Force Field Toolkit (ffTK) in VMD was used to optimize charge, bond distance, angle, and dihedral parameters. Optimized geometries were determined from quantum mechanical calculations. Molecular simulations of the molecules in explicit and implicit water solutions were conducted to assess the abilities of optimized parameters to recapitulate optimized geometries. Calculated infrared (IR) spectra were obtained and compared with experimental IR spectra for validation of the optimized MM parameters.