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1.
用从头计算分子轨道法和密度泛函理论 ,在HF/6 31G 和B3LYP/6 31G 水平上对ClnAlNHn 和HnAlNHn(n =1~ 3)及其碎片分子的几何构型、电子结构、振动光谱和化学热力学性质进行了理论研究。结果表明 ,优化几何参数与实验值相吻合。Cl2 AlNH2 和H2 AlNH2 分子中 ,Al-N键为由一个σ键和一个π键组成的双重键 ,旋转势垒分别为 34.10和 5 4 .35kJ·mol- 1。而Cl3AlNH3和H3AlNH3分子中 ,Al-N键为σ型单键 ,对应的旋转势垒为 0 .31和 2 .5 0kJ·mol- 1,有较小的势垒 ,易于旋转。化学热力学计算表明 ,ClnAlNHn 和HnAlNHn 分子中 ,Al-N键能的大小顺序为△Hn =2>△Hn =1>△Hn =3.  相似文献   

2.
在密度泛函理论B3LYP/6-311 G(2df)水平上,对C2BH3异构体进行结构优化和简谐振动频率计算。结果表明C2BH3基态为平面环状结构(1A1,C2V)。分子轨道分析显示基态有一个垂直于分子平面、双电子占据的π分子轨道;其三元环几何中心核独立化学位移(NICS)为较大负值,这些表明基态分子具有较强的芳香性。在相同的理论水平上,本文最后详细地分析了基态的红外振动光谱。  相似文献   

3.
用密度泛函方法 [B3LYP/6- 31 1G(d) ]研究了Si2 P2 分子的各种可能异构体的结构、能量和红外光谱 .结果表明 :Si2 P2 分子有 5个稳定的异构体 ,能量最低的异构体为具有P—P桥键的蝴蝶形结构 ,其次为具有Si—Si桥键的菱形结构 ,而具有Si—Si中心键的直线结构能量最高 .并进一步将Si2 P2 和C2 N2分子在结构和能量上的差异进行了比较和分析 .  相似文献   

4.
利用扫描隧道显微技术(STM)研究了3种异代酯基Janus枝状分子(G1G2COOCH3, G0G3COOCH3, G1G3COOCH3)在高定向裂解石墨(HOPG)表面的组装结构. 室温下, G1G2COOCH3, G0G3COOCH3和G1G3COOCH3分别在表面形成有序、局部有序及无序结构. 将样品加热至60~80 ℃后, 表面无序结构可以转化为有序的二聚体密堆积结构. 实验结果表明, 随着枝状分子代数的增加, 分子之间及分子与基底之间作用力增强, 室温下分子组装行为更依赖于分子吸附动力学过程, 组装结构趋于无序化, 而加热可以增强枝状分子在表面的活动性, 调整分子的位置关系, 使表面无序结构转化为热力学稳定的有序二聚体密堆积组装结构.  相似文献   

5.
本工作合成了一系列外围以三缩四乙二醇单甲醚修饰的烷基芳醚骨架两亲性树枝形聚合物Gn(n=0—3),化合物通过了1H-NMR,IR和MALDI-TOF-MS的表征.利用吸收光谱,稳态和时间分辨荧光光谱研究了水溶液中Gn对尼罗红分子的增溶作用以及Gn内部微环境的极性.研究结果表明,高代数树枝形聚合物Gn对尼罗红具有更好的增溶效果.1—3代树枝形聚合物Gn内部疏水孔腔微环境极性随代数增加而逐渐降低,G1和G2树枝形聚合物具有相似的微环境极性,而由于构象的变化使G3具有更加疏水的微环境.  相似文献   

6.
芘和蒽作为荧光探针探测树枝形聚合物微环境   总被引:2,自引:0,他引:2  
郑少君  袁钊  曾毅  李迎迎  李嫕 《物理化学学报》2008,24(10):1785-1789
分别以芘和(9-蒽基)甲基三甲基溴化铵(An)作为荧光探针研究了一系列羧基为外围末端基团的芳醚树枝形聚合物Gn(n=1-4)的内部微环境极性及包结情况. 芘荧光I1/I3值在1-3代树枝形聚合物钾盐水溶液中变化不大, 而3到4代有一个陡降, 推测1-3代树枝形聚合物处于相对开放的结构, G4为相对密闭的球形结构, 4代树枝形聚合物表现出更好的包结特性. An在树枝形聚合物G2钾盐水溶液中的荧光光谱结果表明, 树枝形聚合物G2可以包结两个以上的An分子, An分子疏水的蒽环部分位于树枝形聚合物内部孔穴中, 而带正电荷的铵离子靠近树枝形聚合物分子的极性末端.  相似文献   

7.
去氢抗坏血酸分子振动光谱的理论研究   总被引:1,自引:0,他引:1  
采用RHF, MP2, DFT(B3LYP)方法, 以6-311++G**为基组研究了去氢抗坏血酸分子(DHA)的平衡几何构型和振动光谱. 计算结果表明, 采用RHF, B3LYP以及MP2 方法优化得到的几何结构以及频率值是一致的. 采用B3LYP/6-311++G**计算了DHA分子平衡构型下的谐振动力场﹑振动频率和振动强度. 使用Wilson的GF矩阵方法对DHA分子进行了简正坐标分析, 依据所得的势能分布对DHA分子的振动基频进行了合理的理论归属.  相似文献   

8.
3,3'-二硝基双呋咱醚(FOF-1)合成、晶体结构及理论研究   总被引:2,自引:0,他引:2  
以二硝基呋咱(DNF)为原料,碱性条件下通过DNF分子间硝基醚化合成了3,3'-二硝基双呋咱醚(FOF-1),产率67%,采用红外光谱、核磁共振、质谱及元素分析进行了结构表征.初步探讨了硝基分子间醚化合成FOF-1反应机理,确定了分子间醚化的最佳条件.培养了FOF-1单晶,X射线单晶衍射分析结果表明:FOF-1晶体结构属正交晶系,空间群为P2(1)2(1)2(1),a=6.507(3)nm,b=7.342(4)nm,c=18.721(9)nm,α=90°,β=90°,γ=90°,Dc=1.813g·cm-3;用B3LYP方法在6-31G(d,p)基组水平上对FOF-1的结构进行了计算,得到了其稳定的几何构型和键级.在振动分析的基础上求得体系在不同温度下的热力学性质,并得到了温度对热力学性能影响的关系式.探讨了其热解机理,计算出醚键断裂时的的活化能为234.12kJ·mol-1.  相似文献   

9.
裴伟伟 《大学化学》2004,19(1):60-62
L .G .Wade ,Jr新编的《有机化学》(第 5版 )由PearsonEducationInc于 2 0 0 3年正式出版[1] 。该书是为一年的有机化学课程编写的。全书正文及附录共 1 2 2 0页。正文基本是按照传统的官能团分类法编排的。全书共 2 6章 ,依次为 :①导言和评论 ;②有机分子的结构和性质 ;③烷烃的结构和立体化学 ;④化学反应的研究 ;⑤立体化学 ;⑥卤代烃 ;⑦烯烃的结构和合成 ;⑧烯烃的反应 ;⑨炔烃 ;⑩醇的结构和合成 ; 醇的反应 ; 红外光谱和质谱 ; 核磁共振光谱 ; 醚、环氧化合物和硫醚 ; 共轭体系、轨道对称性和紫外光谱 ; 芳香化合物 …  相似文献   

10.
尼罗红为探针对芳醚树枝形聚合物微环境的研究   总被引:1,自引:1,他引:0  
本工作合成了一系列羧基为外围末端基团的芳醚树枝形聚合物Gn(n=1—4),利用吸收光谱,稳态和时间分辨荧光发射光谱研究了Gn对尼罗红分子的增溶作用和Gn微环境极性.研究结果表明,尼罗红在Gn中的溶解度随代数增加而增大,从G1到G4,尼罗红溶解度相比水中分别增加了3、35、47和215倍.Gn的微环境极性比水低,2-4代芳醚树枝形聚合物具有相似的微环境极性.  相似文献   

11.
5,10,15,20-四(对氯苯基)卟啉羟基稀土配合物的光谱研究   总被引:8,自引:0,他引:8  
研究了四(对氯苯基)卟啉及其羟基稀土配合物的紫外-可见光谱、红外光谱和拉曼光谱,对主要谱带进行了经验归属,讨论了中心离子对紫外光谱和共振拉曼光谱结构敏感带频率的影响.  相似文献   

12.
The Molecular structure, conformational stability and vibrational frequencies of succinonitrile NCCH2CH2CN have been investigated with ab initio and density functional theory (DFT) methods implementing the standard 6-311++G* basis set. The potential energy surfaces (PES) have been explored at DFT-B3LYP, HF and MP2 levels of theory. In agreements with previous experimental results, the molecule was predicted to exist in equilibrium mixture of trans and gauche conforms with the trans form being slightly lower in energy. The vibrational frequencies and the corresponding vibrational assignments of succinonitrile in both C2h and C2 symmetry were examined theoretically and the calculated Infrared and Raman spectra of the molecule were plotted. Observed frequencies for normal modes were compared with those calculated from normal mode coordinate analysis carried out on the basis of ab initio and DFT force fields using the standard 6-311++G* basis set of the theoretical optimized geometry. Theoretical IR intensities and Raman activities are reported.  相似文献   

13.
Infrared spectra (4000–50 cm−1) of the vapor, amorphous and crystalline solids and Raman spectra (3600–10 cm−1) of the liquid with qualitative depolarization data as well as the amorphous and crystalline solids of methylaminothiophosphoryl difluoride, CH3N(H)P(=S)F2, and three deuterated species, CD3N(H)P(=S)F2, CH3N(D)P(=S)F2, and CD3N(D)P(=S)F2, have been recorded. The spectra indicate that in the vapor, liquid and amorphous solid a small amount of a second conformer is present, whereas only one conformer remains in the low temperature crystalline phase. The near-infrared spectra of the vapor confirms the existence of two conformers in the gas phase. Asymmetric top contour simulation of the vapor shows that the trans conformer is the predominant vapor phase conformer. From a temperature study of the Raman spectrum of the liquid the enthalpy difference between the trans and near-cis conformers was determined to be 368±15 cm−1 (4.41±0.2 kJ/mol), with the trans conformer being thermodynamically preferred. Ab Initio calculations with structure optimization using the 6-31G(d) and 6-311+G(d,p) basis sets at the restricted Hartree–Fock (RHF) and/or with full electron correlation by the perturbation method to second order (MP2) support the occurrence of near-trans (5° from trans) and near-cis (20° from cis) conformers. From the RHF/6-31G(d) calculation the near-trans conformer is predicted to be the more stable form by 451 cm−1 (5.35 kJ/mol) and from the MP2/6-311+G(d,p) calculation by 387 cm−1 (4.63 kJ/mol). All of the normal modes of the near-trans rotamer have been assigned based on infrared band contours, depolarization values and group frequencies and the assignment is supported by the normal coordinate calculation utilizing harmonic force constants from the MP2/6-31G(d) ab initio calculations.  相似文献   

14.
六方稀土氧化物在空气中极易水化和碳酸化。测定并讨论了光谱纯粉晶RE2O3(RE= La ,Pr,Nd) 样品的Raman 光谱、红外光谱及粉晶X 射线衍射谱。结果表明, 其水化产物为RE(OH)3 , 碳酸化产物主要为六方双氧单碳酸盐RE2O3CO3 以及少量的单氧双碳酸盐RE2O(CO3)2 和四方RE2O2CO3 。  相似文献   

15.
Vibrational (IR and Raman) spectra for the metal-free phthalocyanine (H2Pc) have been comparatively investigated through experimental and theoretical methods. The frequencies and intensities were calculated at density functional B3LYP level using the 6-3 IG(d) basis set. The calculated vibrational frequencies were scaled by the factor 0.9613 and compared with the experimental result. In the IR spectrum, the characteristic IR band at 1008.cm^-1 is interpreted as C-N (pyrrole) in-plane bending vibration, in contrast with the traditional assigned N-H in-plane or out-of-plane bending vibration. The band at 874 cm^-1 is attributed to the isoindole deformation and aza vibration. In the Raman spectrum, the bands at 540, 566, 1310, 1340, 1425, 1448 and 1618 cm^-1 are also re-interpreted. Assignments of vibrational bands in the IR and Raman spectra are given based on density functional calculations for the first time. The present work provides valuable information to the traditional empirical assignment and will be helpful for further investigation of the vibration spectra of phthalocyanine analogues and their metal complexes.  相似文献   

16.
Infrared and Raman spectra of 1,1-(methylphosphinylidene) bis(methanamine) [mpbm, (CH3)PO(CH2NH2)2] and its N,N′-coordinated Pt(II) and Pd(II) have been studied in the 4000–200 cm−1 frequency range. Ab initio calculations have been carried out for different conformations of the mpbm at HF/6-31G* level of the theory from which structural parameters, conformational stability and predicted infrared and Raman spectra have been obtained. A complete vibrational assignment of the lowest energy conformer, tttg, as well as of its N,N′-coordinated Pt(II) and Pd(II) chloro-complexes was done on the basis of the calculated frequencies, relative infrared intensities, Raman activities and potential energy distribution (PED). The theoretical predictions are compared with the experimental results where appropriate.  相似文献   

17.
Raman spectra of cyclopropylmethyl dichlorosilane (c-C3H5)SiCl2CH3 as a liquid were recorded at 293 K and polarization data were obtained. Additional Raman spectra were recorded at various temperatures between 293 and 163 K, and intensity changes of certain bands with temperature were detected. No crystallization was ever obtained in the Raman cryostat in spite of extensive annealing. The infrared spectra have been studied as a vapour, as an amorphous solid at 78 K and as a liquid in the range 600-100 cm−1. No infrared bands present in the vapour or liquid seemed to vanish upon cooling, and the sample never formed crystals on the CsI window of an infrared cryostat.The compound exists a priori in two conformers, syn and gauche, and the experimental results suggest an equilibrium in which the gauche conformer has 1.64 kJ mol−1 lower enthalpy than syn in the liquid, leading to 20% syn at ambient temperature. Most of the syn bands were situated close to the corresponding gauche bands and it was difficult to obtain reliable ΔH values.B3LYP calculations with various basis sets and the CBS-QB3 and G2 and G3 models were employed, yielding the conformational enthalpy difference ΔH (syn-gauche) between 2.6 and 3.4 kJ mol−1. Infrared and Raman intensities, polarization ratios and vibrational frequencies for the syn and gauche conformers were calculated. Instead of scaling the calculated wavenumbers in the harmonic approximation, calculations from B3LYP/cc-pVTZ were derived in the anharmonic approximation. In most cases these values were in good agreement with the experimental results for 38 observed modes of the gauche and 8 modes of the syn conformer with a deviation of ca. 1%.  相似文献   

18.
The molecular geometries of the anions of nitromethane and 2-nitropropane were optimised and their harmonic force fields were calculated by the RHF/6-311G(d,p), MP2/6-311G(d,p) and B3LYP/6-311G(d,p) methods. The force fields obtained made it possible to reliably interpret the IR and Raman spectra of the Na+ salt of nitromethane, d2-nitromethane and 2-nitropropane. The assignment proposed significantly improves the interpretation of vibrational spectra known so far. Some general conclusions on geometry and vibrational spectra of the salts of mononitroalkanes studied are made. The hybrid density functional method used (B3LYP) is shown to be in better agreement with experimental data available than the Hartree–Fock methods.  相似文献   

19.
Infrared spectra of 3,3,3-trifluoropropyltrichlorosilane (CF3CH2CH2SiCl3) were obtained in the vapour, amorphous and crystalline solid phases in the range 4000-50 cm-1. Additional spectra in argon matrices at 5.0 K were recorded before and after annealing to 20-36 K. Raman spectra of the compound as a liquid were recorded at various temperatures between 298 and 210 K and spectra of the amorphous and crystalline solids were obtained. The spectra suggested the existence of two conformers (anti and gauche) in the fluid phases and in the matrix. When the vapour was shock-frozen on a cold finger at 80 K and subsequently annealed to 120-150 K, six weak or very weak Raman bands vanished in the crystal. Similar variations were observed in the corresponding infrared spectra after annealing and four very weak IR bands disappeared after crystallization. From intensity variations between 298 and 210 K of three Raman band pairs an average value Delta(conf)H degrees (gauche-anti)=6.1+/-0.5 kJmol-1 was obtained in the liquid. Annealing experiments indicate that the anti conformer also has a lower energy in the argon matrices. The conformational equilibrium is highly shifted towards anti in the liquid, and the low energy conformer also forms the crystal. The spectra of the abundant anti conformer and the few bands ascribed to the gauche conformer have been interpreted. Ab initio calculations at the HF/6-311G(**) and B3LYP/6-311G(**) gave optimized geometries, infrared and Raman intensities and vibrational frequencies for the anti and gauche conformers. The conformational energy differences derived were 11.8 and 9.2 kJmol-1 from the HF and the B3LYP calculations, respectively.  相似文献   

20.
The Fourier Transform Infrared spectrum of (S)-4 ethyl-4-hydroxy-1H-pyrano [3',4':6,7]-indolizino-[1,2-b-quinoline-3,14-(4H,12H)-dione] [camptothecin] was recorded in the region 4000-400 cm(-1). The Fourier Transform Raman spectrum of camptothecin (CPT) was also recorded in the region 3500-50 cm(-1). Quantum chemical calculations of geometrical structural parameters and vibrational frequencies of CPT were carried out by MP2/6-31G(d,p) and density functional theory DFT/B3LYP/6-311++G(d,p) methods. The assignment of each normal mode has been made using the observed and calculated frequencies, their IR and Raman intensities. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FT-IR and FT-Raman spectra. Most of the computed frequencies were found to be in good agreement with the experimental observations. The isotropic chemical shifts computed by (13)C and (1)H NMR analysis also show good agreement with experimental observations. Comparison of calculated spectra with the experimental spectra provides important information about the ability of computational method to describe the vibrational modes of large sized organic molecule.  相似文献   

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