水合硼氧酸盐结晶过程中液相的红外光谱

使用差示红外光谱的方法记录了MgB4O7.9H2O,NaB5O8.5H2O,MgB6O10.7H2O和MgB6O10.7.5H2O过饱和水溶液结晶析出相应固相时液相中多聚硼氧配阴离子的变化。结果得出,硼氧酸盐水溶液的红外光谱在800－1000cm^-1波数范围内,存在多种多聚硼氧配阴离子的特征峰,并对振动光谱频率进行了归属。870,810cm^-1为三硼氧配阴离子特征峰;844cm^-1为四硼氧配阴离子特征峰;929cm^-1为五硼氧配阴离子特征峰;959cm^-1为六硼氧配阴离子的特征峰。     

一种电致发光有机化合物的合成及其发光性能的检验

制备了有机电致发光材料1,3-二[（4′-特丁基苯基）-（1″,3″-噁二唑-5）]-苯（以下简写作OXD-7）,通过核磁共振光谱、红外光谱对其结构进行了表征。利用紫外可见吸收光谱、荧光光谱和循环伏安法等研究了其最高被占用分子轨道（HOMO）及最低空余分子轨道（LUMO）能级及发光性能。OXD-7的HOMO能级为5．24eV,LUMO能级为1．69eV。OXD-7在306nm波长处有一吸收峰。采用300nm的紫外光激发,荧光发射峰值波长为366．6nm。     

氟磺酸氟振动光谱的从头算

采用从头算HF／SCF方法以6-31G基组研究了FOSO2F分子的几何结构、振动谐性力场和红外光谱强度．理论力场由Pulay的标度量子力学方法进行标度,计算得到的振动频率与实验值比较平均偏差为6．3cm-1．根据振动频率的势能分布和从头算红外光谱强度值对此分子的振动基频进行了理论归属．     

XSO_2NCO(X=F,Cl)分子振动光谱的从头算研究——谐性力场和频率分布

采用从头算方法以 6 31G 基组对XSO2 NCO(X =F ,Cl)分子的振动谐性力场和红外光谱进行了研究 .由最小二乘法通过拟合FSO2 NCO分子的理论和实验频率优化了一套力常数校正因子 ,然后将其迁移到ClSO2 NCO分子中 ,以产生一个纯理论预测的振动基频 .利用校正后的力场计算得到FSO2 NCO和ClSO2 NCO的振动频率 ,与实验值比较平均偏差分别为 3cm-1和 5cm-1.根据用校正后力场进行简正坐标分析得到的势能分布 (PED)和从头算红外光谱强度值对此二分子的振动基频的指认进行了讨论 .     

对二甲苯分子和离子态振动光谱的理论计算

利用Gaussian98从头计算程序在6 31G计算水平下对对二甲苯（p C8H10）分子和离子态进行了几何优化及其振动光谱的理论计算.计算的分子第一激发态振动光谱与实验结果相当符合，同时计算了离子态的振动频率，并对实验的离子振动光谱谱峰进行标识，其中在341 cm－1处谱峰的振动模为3.     

PVP/HEC分子间缔合作用机理探讨

通过粘度、紫外光谱、红外光谱和DSC谱的测定,探讨了PVP/HEC分子间的缔合机理.结果表明,PvP/HEC复合体系相对于单一体系产生了粘度的负协同效应,NaCl的加入使单一体系和复合体系的粘度均下降;在紫外可见吸收光谱中,PVP/HEC复合体系的最大吸收波长λmax相对于PVP、HEC各自的λmax都发生红移;PVP/HEC复合物的红外光谱在2370 cm-1出现新的吸收峰;DSC谱中复合物的峰温高于简单混合物,而其焓变低于简单混合物,这一切均证明HEC与PVP之间未发生疏水缔合,而是HEC的羟基与PVP的羰基之间通过氢键缔合成复合物,复合物的分子链排列较为紧密.     

丙氨酸晶体太赫兹振动光谱的实验和理论研究

利用太赫兹时域光谱和低频拉曼光谱仪研究了丙氨酸晶体在0.2-2.6 THz 范围内的太赫兹吸收和拉曼散射光谱. 研究表明: 在该低频范围有四个振动模式, 其中两个只具有拉曼活性, 其余两个同时具有红外和拉曼活性. 基于B3LYP杂化密度泛函的自洽场晶体轨道法对丙氨酸周期性结构进行了理论研究和光谱计算. 通过比较实验和理论结果, 指认了实验光谱特征峰所属的不可约表示. 通过理论计算得到的图形, 得出在此低频范围的振动模式主要包含分子间氢键的扭转和摇摆运动.     

三(4-硝基苯基)甲烷衍生物的结构和振动光谱的理论研究（英文）

用密度泛函理论优化了三苯甲烷(1)和一系列三(4-硝基苯基)甲烷衍生物2,3和4的几何结构,并计算了其红外光谱和拉曼光谱;通过与实验光谱的对比,对实验光谱中的谱峰进行了指认,并从理论上纠正了部分对3和4红外光谱谱峰不合适的实验指认;同时预测了2,3和4的拉曼光谱.结果表明,几种化合物的振动光谱计算结果与相应的实验结果吻合良好;且化合物2,3和4的拉曼光谱具有相似性.     

微波硫灯发射光谱的理论模拟

通过实验观测了微波硫灯的发光光谱. 利用从头计算的多组态准简并微扰理论方法, 采用cc-pVQZ基组计算了S2分子B3Σu--X3Σg-态和B″3Πu-X3Σg-态的跃迁矩及其振动态之间跃迁的弗兰克-康登因子, 导出了S2分子振动分辨发射谱. 同时, 利用含时密度泛函方法计算了Sn(n=2~8)分子的吸收谱. 将计算得到的S2分子振动分辨发射谱与实验所测得的光谱分布进行了比较分析, 解释了微波硫灯的宽谱区发光光谱的特性.     

水杨醛缩苯乙酰腙对阴离子的识别研究

设计合成了用于识别阴离子的荧光传感分子水杨醛缩苯乙酰腙(1),通过红外光谱、核磁共振谱和质谱表征其结构;利用其光谱性质研究了该物质对几种阴离子的识别性质,初步探讨了其结合模式。实验表明:在乙腈介质中,受体分子1表现出对F-良好的选择性,F-的加入导致1在478 nm处荧光增强44倍,而其它阴离子只引起1的荧光略微增强,Job法实验得出1与F-的结合比为1∶1。     

Comparative molecular field analysis of artemisinin derivatives: Ab initio versus semiempirical optimized structures

Based on the belief that structural optimization methods, producing structures more closely to the experimental ones, should give better, i.e. more relevant, steric fields and hence more predictive CoMFA models, comparative molecular field analyses of artemisinin derivatives were performed based on semiempirical AM1 and HF/3-21G optimized geometries. Using these optimized geometries, the CoMFA results derived from the HF/3-21G method are found to be usually but not drastically better than those from AM1. Additional calculations were performed to investigate the electrostatic field difference using the Gasteiger and Marsili charges, the electrostatic potential fit charges at the AM1 level, and the natural population analysis charges at the HF/3-21G level of theory. For the HF/3-21G optimized structures no difference in predictability was observed, whereas for AM1 optimized structures such differences were found. Interestingly, if ionic compounds are omitted, differences between the various HF/3-21G optimized structure models using these electrostatic fields were found.     

A comparative molecular field analysis (CoMFA) study using semiempirical, density functional, ab initio methods and pharmacophore derivation using DISCOtech on sigma 1 ligands

The Comparative Molecular Field Analysis (CoMFA) was developed to investigate a three-dimensional quantitative structure activity relationship (3D-QSAR) model of ligands for the sigma 1 receptor. The starting geometry of sigma-1 receptor ligands was obtained from the Tripos force field minimizations and conformations were decided from DISCOtech using the SYBYL 6.8. program. The structures of 48 molecules were fully optimized at the ab initio HF/3-21G* and semiempirical AM1 calculations using GAUSSIAN 98. The electrostatic charges were calculated using several methods such as semiempirical AM1, density functional B3LYP/3-21G*, and ab initio HF/3-21G*, MP2/3-21G* calculations within GAUSSIAN 98. Using the optimized geometries, the CoMFA results derived from the HF/3-21G method were better than those from AM1. The best CoMFA was obtained from HF/3-21G* optimized geometry and charges (R2 = 0.977). Using the optimized geometries, the CoMFA results derived from the HF/3-21G methods were better than those from AM1 calculations. The training set of 43 molecules gave higher R2 (0.989-0.977) from HF/3-21G* optimized geometries than R2 (0.966-0.911) values from AM1 optimized geometries. The test set of five molecules also suggested that HF/3-21G* optimized geometries produced good CoMFA models to predict bioactivity of sigma 1 receptor ligands but AM1 optimized geometries failed to predict reasonable bioactivity of sigma 1 receptor ligands using different calculations for atomic charges.     

适用于液晶大分子的量子化学计算方法以及六烷氧基苯并菲取代的1,3,5-三酰胺苯液晶的研究

盘状液晶分子之间的相互作用决定液晶的性质. 为了选择合适的计算方法, 以便用量子化学研究液晶大分子, 设计了对位取代苯和三酰胺苯作为模型分子, 用高水平的ONIOM [MP2/6-31G*(0.25):HF/6-31G(d,p)]计算提供了与晶体结构资料相符合的较准确的二体相互作用结果. 然后与各种较低级别的计算进行比较, 说明ONIOM (HF/STO-3G: AM1:UFF)水平比较合适. 盘重叠部分的相互作用主要是色散作用, 用UFF力场处理, 氢键主要是静电作用, 用HF/STO-3G处理, 其余部分用AM1处理. 通过对苯取代的1,3,5-三酰胺苯的双分子构型优化, 并与晶体结构数据进行比较, 进一步说明ONIOM (HF/STO-3G:AM1:UFF)水平计算的适用性. 在此基础上, 对六烷氧基苯并菲取代的1,3,5-三酰胺苯的双分子构型进行了优化, 为解释它所形成的液晶具有较高的电荷传输能力提供了有用的信息.     

Raman imaging of fluid inclusions in garnet from UHPM rocks (Kokchetav massif, Northern Kazakhstan)

In this work, we will report a combined experimental and theoretical study on molecular and vibrational structure of N,N'-di(p-thiazole)formamidine (DpTF). DpTF has been synthesized and characterized by elemental analysis, FT-IR, FT-Raman, 1H NMR, 13C NMR spectroscopy and X-ray single crystal diffraction. The FT-IR and FT-Raman spectra of DpTF were recorded in the solid phase. The optimized geometry was calculated by HF and B3LYP methods using 6-31G(d) basis set. The FT-IR and FT-Raman spectra of DpTF was calculated at the HF/B3LYP/6-31G(d) level and were interpreted in terms of potential energy distribution (PED) analysis. The scaled theoretical wavenumber showed very good agreement with the experimental values. A detailed interpretation of the infrared and Raman spectra of DpTF was reported. On the basis of vibrational analyses, the thermodynamic properties of the title compound at different temperatures have been calculated, revealing the correlations between Cp,m°, Sm°, Hm° and temperatures. Furthermore, molecular electrostatic potential maps (MESP) and total dipole moment properties of the compound have been calculated.     

Hydrogen bonding. Part. 76. Molecular orbital investigation of the stability of tertiary amine-hydrogen fluoride compounds in aqueous solution

N,N-Dimethyl-1-adamantamine-hydrogen fluoride (2MAAHF) does not dissociate in aqueous solution, while 2MAAHCl and 2MAAHBr readily ionize in H₂O. Semi-empirical (AM1-SM2) calculations demonstrate that the enthalpic barrier to dissociation of 2MAAHF in aqueous solution is four times as high as that of 2MAAHCl and three times as high as that of 2MAAHBr. Ab initio calculations (3-21G(*) and 3-61G^*) show that 2MAAHF is a tightly bound molecular complex between neutral HF and neutral amine, with a low dipole moment and little negative charge exposed on fluorine. 2MAAHCl and 2MAAHBr are ion-pairs with an electrostatic hydrogen bond between cation and anion, large dipole moments, and exposed halogen atoms with high electrostatic potential; these factors explain the ease of ionization of 2MAAHCl and 2MAAHBr. Parallel studies on other tertiary amines give similar results.     

Ab Initio Study of Ring Flipping of the Overcrowded Peri-Substituted Naphthalenes

Ab inintio molecular orbital and density functional theory method were used to investigate the structural and dynamic behavior of 1,8-di-tert-butyl naphthalene (1), 1,8-bis(trimethylsilyl)naphthalene (2), 1,8-bis(trimethylgermyl)naphthalene (3), and 1,8-bis(trimethylstannyl)naphthalene (4). HF/3-21G//HF/3-21G results revealed that the ring flipping barrier height of compound 1–4 is 92.59, 32.13, 26.76, and 15.46 kJ mol^?1 respectively. The obtained results show that the transition state structure for ring flipping of the bulky-groups is in a planar form with naphthalene ring. Contrary to compound 1, the ring flipping of compounds 2–4 occurred easily at room temperature. Also, MP2/3-21G//HF/3-21G energy calculation, show that the enantiomerization energy of compounds 1–4 are 97.99, 33.24, 26.80, and 15.38 kJ·mol^?1 respectively. The required energy for ring inversion of compounds 1–4 are 85.09, 27.26, 21.54, and 10.21 kJ mol^?1 respectively, as calculated by B3LYP/3-21G//HF/3-21G method. It can be concluded that the lower energy barrier of the ring flipping of compounds 2–4 is related to the increasing of the bond lengths of Si—C, Ge—C, and Sn—C, in contrast to C—C bond.     

Copolymers of carbon dioxide and nitrogen: an AM1 and ab initio computational study

Extending work by various groups on possible dimers, trimers, etc. of dinitrogen and of carbon dioxide, the authors have studied analogous copolymers of N₂ and CO₂ computationally. Twelve cyclic structures were examined with the AM1, HF/3-21G, HF/6-31G* and MP2(FC)/6-31G* methods, and the acyclic “monomer” to “tetramer” HO(C(O)O–N= N–)_nH, n=1–4, were studied at the AM1 and HF/3-21G levels; the cyclic species included 2-oxa-3,4-diazacyclobut-3-ene-1-one, 2-oxa-3,4,5,6-tetraazacyclohexa-3,5-diene-1-one, and various aza/oxa bicyclo[2.2.0] and bicyclo[2.2.2] systems. For the cyclic species, it was concluded that only the MP2(FC)/6-31G* results, which differ considerably from those at the other three levels, are likely to be reliable. These MP2 calculations indicate that only seven of the 12 cyclic structures studied are stationary points (one is a transition structure), and none of them is kinetically stable at room temperature. Although some have high energy densities (ca. 7–10 kJ g⁻¹), their expected low kinetic stabilities seems to make this of little practical value. The acyclic “copolymers” were all relative minima at the AM1 and HF/3-21G levels; unlike the cyclic species, their kinetic stabilities were not investigated directly by comparing the energies of reactants and decomposition transition states. The energy density of the infinite acyclic polymer was found by extrapolation to be 5.1 (AM1) or 5.6 (3-21G) kJ g⁻¹. The calculated vibrational spectra of the MP2 stationary points and of the acyclic molecules gave some indication of instability by the presence of low-frequency modes leading in the limit to decomposition.     

Intermolecular Interaction of HMX： an Application of ONIOM Methodology

IntroductionExtensive studies on intermolecular interac-tions have been made in the past decades due totheir importance in a wide range of physical,chem-ical and biological fields.Researches on the weakintermolecular interactions began with hydrogenbonds.Scheiner summarized the ab initio investiga-tions on hydrogen bonding in detail[1] .With the abinitio method supermolecular structures and bind-ing energies can be predicted notonly for H- bondedsystems but also for other systems[2 _ 5] when …     

Experimental and theoretical investigation of the first overtone spectrum of 1,3,5-trinitrotoluene

Vibrational overtone spectroscopy is a powerful tool for studying intramolecular and intermolecular interactions. We report on a combined experimental and modeling study of the C-H stretch first overtone of bulk 1,3,5-trinitrotoluene (TNT) and TNT on fumed-silica powder. We recorded the overtone spectra by laser photoacoustic spectroscopy and compared them with those predicted with the harmonically coupled anharmonic oscillator model in the 5600-6600 cm(-1) region. The model systems included single molecules and hybrid quantum and molecular mechanical (QM:MM) clusters to account for the effects of intermolecular interactions on the observed spectra. We performed the hybrid QM:MM calculations at the HF/6-31+G(d,p), B3LYP/6-31+G(d,p), and MP2/6-31+G(d,p) levels of theory and with the universal force field (UFF) to account for van der Waals and electrostatic effects from surrounding molecules. Overtone spectra calculated from the MP2 level of theory, using a HF/3-21+G* calculation to assign molecular charges in the MM layer, and the Merz-Singh-Kollman population analysis for assigning partial charge in the QM layer and determining the transition dipole moment agreed best with the experimental data.