天然Alboatisin电子结构和圆二色谱的密度泛函理论研究

采用蒙特卡罗MMFF94分子力学力场方法搜索一类新发现的生物活性分子Alboatisin A～C的稳定构象,用梯度校正的B3LYP方法,计算其稳定构象的旋光度、振动圆二色谱(VCD)、电子圆二色谱(ECD)等光学活性,并从微观的角度对VCD谱和ECD谱中强或弱的正或负康登效应进行归属．从分子结构、电子结构和分子振动分析了分子手性的微观起源．结果表明,计算与实验的旋光度值相吻合,OH的取代位置与数目可调控旋光度发生在手性骨架上的振动或电子跃迁转移是手性光谱产生的重要原因．Alboatisin的圆二色谱是手性骨架变形振动的光谱响应,是不对称电子跃迁的光谱响应结果．     

银杏内酯分子结构和光谱性质的理论研究

采用密度泛函理论方法详细考察四种银杏内酯分子(银杏内酯A、B、C和J)的结构和光谱性质.研究发现,改变银杏内酯上的取代基,银杏内酯分子骨架具有相对稳定的结构.基于优化得到的稳定结构,我们计算得到了四种银杏内酯分子的红外(Infrared,IR)光谱、拉曼(Raman)光谱和振动圆二色(Vibrational circular dichroism,VCD)光谱性质.我们发现,四种银杏内酯分子的IR光谱图在1100 cm-1有较明显的区别,这些振动峰主要是银杏内酯分子中C-O-C键的伸缩振动峰.在Raman光谱图中,波长在3600cm-1处为银杏内酯分子中羟基的伸缩振动,银杏内酯A、银杏内酯B、银杏内酯C分裂成了两个强度不等的振动峰,而银杏内酯J分子表现为一个宽的振动峰.在VCD光谱图中,我们发现四种银杏内酯分子在3800 cm-1附近有明显的区别.     

对巯基苯胺分子构象和拉曼光谱的密度泛函理论研究

本文采用密度泛函方法B3LYP/6-311+G**计算了对巯基苯胺分子(PATP)的平衡结构和振动拉曼光谱。结果表明该分子有两个稳定构象,反式构象能更低。利用振动模分析所得的势能分布我们对该分子振动基频进行了归属,并计算了低能构象的标度振动频率,其结果与实验值相吻合。     

硝酸丙酯结构、振动频率和热力学性质的密度泛函理论研究

用密度泛函理论(DFT)研究硝酸丙酯化合物的分子结构、振动光谱和热力学等基本性质.取BLYP、B3LYP方法和6-31G*、6-31G**、6-311G*、6-311G**基组,对硝酸丙酯分子的几何构型进行全优化计算并分析其电子结构性质.和考虑了二级相关能校正的MP2/6-311G*计算结果比较表明,B3LYP/6-31G*是研究许多较大体系化合物卓有成效和颇有前途的方法.在B3LYP/6-31G*的水平上对优化后的结构进行了正则振动频率分析,用因子0.95校正后的振动光谱和实验结果比较,符合较好.进一步     

3-氨基-2,5-二氯苯甲酸振动光谱的密度泛函研究

为了本质地把握3-氨基-2,5-二氯苯甲酸(3A2,5DBA)的振动光谱和结构间的关系,在HF和B3LYP水平上利用6-311G(d,p)基组对3A2,5DBA进行了结构优化和振动频率的计算,得到了3A2,5DBA的结构信息和全部45个简正振动模式.通过与苯甲酸的结构参数以及相关文献数据的对比,发现B3LYP/6-311G(d,p)方法较HF/6-311G(d,p)方法能给出更加合理的结果.考虑到计算模拟分子和实验测量样品间的差异,对计算所得到的频率进行了合理的标度修正.在B3LYP/6-311G(d,p)方法下,对波数小于800cm-1的振动频率,标度因子取1.001 3,而波数大于800 cm-1的标度因子取0.961 3.借助Gaussian View程序包对所计算得到的振动模式进行了高精度指认,对3A2,5DBA的主要官能团及取代基团进行了振动分析.通过和实验测量的FTIR数据的比对,发现经标度修正后的计算结果和实验测量符合的很好.同时结合相关的文献报道,表明所做的振动指认和振动分析是合理的.     

基于密度泛函方法的梓醇红外光谱的预测

梓醇是一种具有特殊药理活性的环烯醚萜苷类化合物。采用密度泛函(DFT)B3LYP/6-311G**方法对梓醇分子的几何构型进行全优化,得到其几何构型参数,进一步计算得到梓醇的红外振动光谱,振动频率校正因子为0.96。对计算得到的振动频率进行归属和解析并与实验测定得到的梓醇IR光谱特征峰比较,发现理论计算出的IR光谱与实验测定IR特征峰位具有很好的一致性,说明所采用的DFT方法能够用于梓醇分子几何构型的优化,预测难以得到标准对照品的环烯醚萜苷类化合物的IR光谱数据。     

1-甲基萘的振动分辨激光诱导荧光光谱研究

在超声射流条件下得到了1-甲基萘的激光诱导荧光光谱,并结合理论计算研究了1-甲基萘分子的基态和激发态的几何构型及振动信息.运用DFT方法在B3LYP/6-311++G*的水平上优化了1-甲基萘的基态儿何构型,结果表明1-甲基萘分子基态的S-E和E-S两个构象体中,只有S-E构象体为稳定构型,E-S构象是连接两个S-E构...     

2-氯-5-三氟甲基苯胺水杨醛Schiff碱的结构及光谱性质研究

实验以2-氯-5-三氟甲基苯胺、水杨醛为原料,合成2-氯-5-三氟甲基苯胺水杨醛Schiff碱,测定了Schiff碱的红外光谱和氢谱.利用密度泛函理论(DFT)B3LYP方法在6-311++G**基组上对合成的Schiff碱化合物进行了几何构型的优化和红外光谱的计算,得到了分子的优势构象、频率值及对应的红外强度,并比较了实验和理论计算的光谱数据,对分子的振动模式进行了全面的光谱归属,发现理论计算与实验测试结果吻合的较好.     

三乙胺分子构象与红外光谱的理论研究

利用密度泛函理论B3LYP的方法,在6-311++G(d,p)基组水平上沿二面角φ₁(C9N1C2C5)和φ₂(C16N1C9C12)构成的二维坐标下扫描了–180°—180°范围内构象异构化势能面,甄别出12种三乙胺基态异构体.进一步辅以二阶微扰理论MP2的方法,在相同基组水平下计算与优化6种能量较低的构象异构体的结构与能量.结果表明具有C3对称性的G1与G1’是最稳定构象,并识别出两种具有新的甲基取向的G4与G4’构象异构体.另外,通过G1—G4红外光谱与振动模式的比较,分析了它们之间的相似性与差异性.G1—G4的红外谱线显示在0—1600 cm^–1范围内的强度较弱,而在2800—3300 cm^–1范围内的强度较强,标定出伞状振动与C—H伸缩振动等特征振动模,不同构象所引起的红外谱峰的平均移动量小于20 cm^–1.     

六硝基六氮杂三环十二烷的结构和性能——HEDM分子设计

用密度泛函理论B3LYP方法,在631G基组水平下设计和计算了高能量密度化合物六硝基六氮杂三环十二烷的结构和性质.由分子总能量、前线轨道能级和键集居数等电子结构参数,判别船式(α)比椅式(β)构象稳定.求得其IR谱频率和强度并作归属,报道了200～800K体系的热力学性质.基于理论计算密度和生成热,运用Kamlet公式预示了标题物的爆速和爆压,α构象的爆速和爆压分别为9.46km/s和41.74GPa,β构象则稍低些,分别为9.34km/s和40.02GPa.     

Molecular structure,NMR and vibrational spectral analysis of 2,4‐difluorophenol by ab initio HF and density functional theory

Quantum chemical calculations of energies, geometries and vibrational wavenumbers of 2,4‐difluorophenol (2,4‐DFP) were carried out by using ab initio HF and density functional theory (DFT/B3LYP) methods with 6‐311G(d,p) as basis set. The optimized geometrical parameters obtained by HF and DFT calculations are in good agreement with related molecules. The best level of theory in order to reproduce the experimental wavenumbers is the B3LYP method with the 6‐311G(d,p) basis set. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. A detailed interpretation of the infrared and Raman spectra of 2,4‐DFP is also reported. The entropy of the title compound was also performed at HF/6‐311G(d,p) and B3LYP/6‐311G(d,p) levels of theory. The isotropic chemical shift computed by ¹H, ¹³C NMR analyses also shows good agreement with experimental observations. The theoretical spectrograms for FT‐IR and FT‐Raman spectra of the title molecule have been constructed. Copyright © 2009 John Wiley & Sons, Ltd.     

吉非替尼谱学性质计算研究

吉非替尼是第一个被批准上市用于治疗晚期非小细胞肺癌(NSCLC)的药物．该文采用5种密度泛函理论(DFT)方法B3LYP,BHandHLYP,M06-2X,CAM-B3LYP和LC-wPBE在6-311++G**水平上对吉非替尼分子的红外、紫外可见光谱及核磁共振谱进行了计算,并通过比较计算值和实验值得到最佳的计算条件．研究结果表明,CAM-B3LYP和M06-2X是最佳的用于描述吉非替尼分子红外光谱的方法;B3LYP//GIAO(Gauge-Including Atomic Orbital)方法预测得到的吉非替尼在(CH₃)₂SO中的¹H NMR与实验值最为接近,用于预测¹³C NMR的最佳方法是B3LYP//CSGT(Circularty Sgmmetrical Gabor Transform)．     

Conformational stability and vibrational study of phenylacetyl chloride

The Fourier transform infrared spectroscopy and Fourier transform Raman spectra of phenylacetyl chloride were recorded and analyzed in the range 3500–400 and 3500–200 cm^?1 at room temperature, respectively. In order to obtain the structural information and conformational stabilities, a potential energy surface scan for internal rotation was carried out at the B3LYP/6‐31G(d) level. The potential energy surface reveals that the title compound has two minimal conformers (A and B). The optimized geometries, structural parameters, stabilities, energies, thermodynamic parameters, vibrational wavenumbers, infrared intensities, and Raman activities for the two conformers (A and B) have been obtained by employing B3LYP and MP2 calculations with 6‐311++G (d, p) basis sets. The conformational energy difference between A and B is very small, indicating that the B conformer coexists with the A conformer. The detailed vibrational assignments of vibrational spectra of each conformer have been made on the basis of the potential energy distributions analysis. The highest occupied molecular orbital –lowest unoccupied molecular orbital energy gap and molecular electrostatic potential of the two conformers have been also calculated for comparison of their chemical activities. Copyright © 2015 John Wiley & Sons, Ltd.     

苏丹红Ⅲ与苏丹红Ⅳ的红外、拉曼光谱和密度泛函理论的研究

报道了苏丹红Ⅲ和苏丹红Ⅳ的红外光谱(IR)、固体常规拉曼光谱(NRS)和以新型Cu-Ag复合纳米材料为基底的表面增强拉曼光谱(SERS)。以密度泛函理论(DFT)为基础,采用B3LYP/6-311+G(d,p)基组对其红外和拉曼光谱进行计算,计算结果与实验数据基本吻合,并且运用Gauss view 5.0可视化软件,对峰的振动模式进行了全面的归属。实现了对苏丹红的快速鉴别,为研究苏丹红染料的特性和快速鉴定提供了有利的依据,为食品安全检测提供了可靠的方法。     

Molecular structure,experimental and theoretical 1H and 13C NMR chemical shift assignment of cyclic and acyclic α,β‐unsaturated esters

The experimental ¹H and ¹³C NMR spectra of 13 phenyl cinnamates and four 4‐methylcoumarins were investigated and their chemical shifts assigned on the basis of the two‐dimensional spectra. For the unsubstituted cinnamic acid phenyl ester, optimized molecular structures were calculated at a B3LYP/6‐311++G(d,p) level of theory. ¹H and ¹³C NMR chemical shifts were also calculated with the GIAO method at the B3LYP/6‐311 + G(2d,p) level of theory. The comparison between experimental and calculated NMR chemical shift suggests that the experimental spectra are formed from the superposition spectra of the two lowest energy conformers of the compound in solution. The most stable s‐cis configuration found in our studies is also the conformation adopted for a related phenyl cinnamate in solid state. The experimental results were analyzed in terms of the substituent effects. Copyright © 2013 John Wiley & Sons, Ltd.     

Computational estimates of the gas-phase basicities,proton affinities and ionization potentials of the six isomers of dihydroxybenzoic acid

The gas-phase basicities (GBs), gas-phase proton affinities (PAs) and ionization potentials (IPs) of all six isomers of dihydroxybenzoic acid have been calculated using density functional theory at the B3LYP/6-311++G(2df,p)//B3LYP/6-31+G** level. A detailed conformational analysis of each isomer was performed, and the calculated thermodynamic properties were Boltzmann averaged over all conformations. Respectively, the GBs and the gas-phase PAs vary from 803.8 and 832.5?kJ?mol^?1 for the least basic species (3,5-DHB) to 830.1 and 861.4?kJ?mol^?1 for the most basic isomer (2,4-DHB). The reported GBs and gas-phase PAs of 2,3-DHB and 2,4-DHB, are in excellent agreement with previous experimental measurements. Agreement for the 2,5-DHB and 3,4-DHB isomers are not as good, but still close to or within the experimental error estimates. The calculated values for the GB and gas-phase PA of 2,6-DHB and especially 3,5-DHB are significantly outside the experimental error brackets. Repeating these calculations on the lowest energy conformation of each isomer at the MP2/6-311++G(2df,p)//MP2/6-31+G** level yielded significantly worse results. Our results indicate that protonation in all isomers takes place on the carboxylic sites. The vertical IPs vary from 8.14 eV for 2,5-DHB to 8.56 eV for 2,4-DHB.     

Reaction of C2HCl2+O2: Combined TR-FTIR Spectroscopy and Electronic Structure

用时间分辨傅立叶变换红外发射光谱(TR-FTIR)和G3MP2//B3LYP/6-311G(d,p)水平的电子结构计算研究了环境化学中重要的二氯代乙烯自由基C₂HCl₂和O₂分子的基元反应通道和机理. 通过0.5 cm^-1高分辨的TR-FTIR发射光谱观察到三种振动激发态产物CO₂、CO和HCl,由光谱拟合得到CO和HCl的振动态分布,结合电子结构计算的反应势能曲线,提出反应机理和能量上最可能的反     

Conformational analysis and vibrational spectroscopic studies on dapsone

In this study, the theoretical conformation analysis of free dapsone has been performed by single point energy calculations at both semi-empirical PM3 and DFT/B3LYP-3-21G theory levels and three stable conformers were determined. Both the IR and Raman spectra of the molecule in solid phase have been recorded. The IR intensities and harmonic vibrational wavenumbers of each conformer were calculated by DFT method at B3LYP/6-31++G(d,p) theory level. For the fundamental characterization, the total energy distribution (TED) calculations of the vibrational modes were done using parallel quantum mechanic solution program (SQM) and the fundamental modes were assigned. The theoretical results are in agreement with the experimental ones.     

甘氨酸精氨酸二肽的结构计算和二肽气相最低能构象模型

研究了气相下的甘氨酸精氨酸二肽体系．在考虑三种异构体内轴转动时对势能面进行了系统采样．大量的初始构型经PM3、 HF/3-21G^*、 BHandHLYP/6-31G^*及BHandHLYP/6-311++G^**方法逐级优化获取了最终的稳定构型,低能的结构进一步运用BHandHLYP、cam-B3LYP、 B97D及MP2方法在6-311++G(3df,3pd)基组下进行了单点能计算．计算了重要构象的转动常量、偶极矩、垂直电离能、温度分布及红外光谱．最终数据表明,气相GlyArg主要以电中性的状态存在,参考所有的氨基酸及部分二肽的稳定结构特征,结合各类氨基酸的疏水性,归纳出了各种不同二肽的最低能构象是中性或双电性构型的理论模型．     

A combined experimental and theoretical study on 8-hydroxy-2-quinolinecarboxylic acid

The mid-IR and Raman spectra of 8-hydroxy-2-quinolinecarboxylic acid (8HQC) were recorded. These spectra were interpreted with the help of B3LYP/6–311 ++G(d,p) calculations and potential energy distribution (PED) analysis. As a result of the calculations, seven tautomers were determined among many stable conformations. The experimental spectra were concordant with the theoretical data of one tautomer. In the functional group region overtone and combination bands were detected and assigned. In addition, because of several peaks in the IR spectrum, it was proposed that the 8HQC exhibits dimerization in condensed phase. Possible dimeric forms of 8HQC were evaluated at the same level of theory, and it has been seen that the calculation results confirm the above proposal. ¹H and ¹³C NMR chemical shifts of 8HQC have been calculated, and compared with the experimental data. The frontier molecular orbital properties and the atomic charges were also theoretically obtained and presented.