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1.
分别用HF/4 31G(Si =6 2 1G)、B3LYP/6 31G(D)、B3LYP/6 31G、HF/6 31G、MP2 /6 31G(D)对TMS进行了结构优化 ,在此基础上 ,用Hartree Fock、B3LYP理论水平下 ,分别用不同的基组 6 31G、6 31+ +G(D ,P)、6 311+G(2D ,P)、6 311+ +G(D ,P)进行NMR的计算 ;在MP2理论水平上 ,用STO 3G、3 2 1G、4 31G、6 31G、6 31G(D)、6 31+ +G(D ,P)等基组进行NMR的计算 .并用GAUSSION98程序所给出的四种计算NMR的方法 :GIAO、IGAIM、CSGT、SINGLEGAUGEORIGIN ,分别在上述基础上进行了TMS的屏蔽值的计算 .研究结果表明 ,就理论水平而言 ,DFT(B3LYP)比HF计算结果要好 ,而且基组越大 ,计算精度越高 ,但有一饱和基组存在 .就计算方法而言 ,用GIAO有利于计算精度的提高 .计算结果与实验值基本上吻合  相似文献   

2.
报道了抗癌新药β-榄香烯的13C NMR化学位移的量子化学计算.在分子力学MMX和量子化学RHF/6-31G*或B3LYP/6-31G*优化结构的基础上进行了两种规范变换方法GIAO和CSGT的Hartree-Fock和B3LYP (6-31G*基组)的化学位移计算.并对计算结果进行了误差分析和线性相关分析.所有的这些结果中,采用GIAO规范变换方法都好于CSGT,而以GIAO-B3LYP/6-31G*∥B3LYP/6-31G*计算的结果最好,RMS为4.3ppm,相关系数R2为0.998,SD为2.42ppm.而GIAO-B3LYP/6-31G*∥MMX是一种能兼顾计算时间和计算精度的方法,其RMS、R2和SD分别为4.9、0.996和3.04ppm.  相似文献   

3.
在B3LYP / 6-311G(d,p)水平下对六种香豆素衍生物的结构进行了优化,并通过振动分析验证了其稳定性。利用GIAO方法在B3LYP/6-311G(d,p)水平下研究了香豆素衍生物的NMR谱。研究表明,六个化合物结构共平面性较好,具有较大共轭体系;不同的取代基和取代基的不同位置对几种香豆素衍生物的NMR都有不同的影响。苯环上的氢原子被其他基团取代后,其α-C原子和邻位碳原子的δ值变化明显,而间位碳原子δ值几乎没有变化。取代基的电负性对α-C原子δ值的影响具有一定规律性,而共轭效应对苯环碳原子的影响则更为复杂。最后,为了说明理论计算值与实验值之间的相关性,给出了六种衍生物化学位移值的理论与实验值相关图,并进行线性回归。结果表明,六种香豆素衍生物的化学位移理论与实验值之间的相关性非常好。  相似文献   

4.
应用规范不变原子轨道GIAO法,分别在HF/6-311+G(2d,p)//B3LYP/6-31G(d)和HF/6-311+G(2d,p)//B3LYP/6-31G(d,p)水平上,计算了从卫茅科南蛇藤属植物苦皮藤中分离鉴定出的2,4,6-三甲氧基苯-1-O-D葡萄糖苷(化合物1)的α和β分子构型的1HNMR和13CNMR的化学位移值,并对理论计算值与实验值的误差进行了统计分析,其中β分子构型的计算值与实验值较为接近,结合α和β分子构型的总能量计算值,预测化合物1分子应择型于β构型,即为2,4,6-三甲氧基苯-1-O-β-D葡萄糖苷,这与根据糖的端基质子化学位移和耦合常数实验值(δH=4.81,J=7.3Hz)推断的结论相吻合,进一步说明理论计算的合理性.  相似文献   

5.
在B3LYP/6-311G(d,p)水平下对六种香豆素衍生物的结构进行了优化,并通过振动分析验证了其稳定性。利用GIAO方法在B3LYP/6-311G(d,p)水平下研究了香豆素衍生物的NMR谱。研究表明,六个化合物结构共平面性较好,具有较大共轭体系;不同的取代基和取代基的不同位置对几种香豆素衍生物的NMR都有不同的影响。苯环上的氢原子被其他基团取代后,其α-C原子和邻位碳原子的δ值变化明显,而间位碳原子δ值几乎没有变化。取代基的电负性对α-C原子δ值的影响具有一定规律性,而共轭效应对苯环碳原子的影响则更为复杂。最后,为了说明理论计算值与实验值之间的相关性,给出了六种衍生物化学位移值的理论与实验值相关图,并进行线性回归。结果表明,六种香豆素衍生物的化学位移理论与实验值之间的相关性非常好。  相似文献   

6.
报道了抗癌新药β-榄香烯的13C NMR化学位移的量子化学计算.在分子力学MMX和量子化学RHF/6-31G*或B3LYP/6-31G*优化结构的基础上进行了两种规范变换方法GIAO和CSGT的Hartree-Fock和B3LYP (6-31G*基组)的化学位移计算.并对计算结果进行了误差分析和线性相关分析.所有的这些结果中,采用GIAO规范变换方法都好于CSGT,而以GIAO-B3LYP/6-31G*//B3LYP/6-31G*计算的结果最好,RMS为4.3ppm,相关系数R2为0.998,SD为2.42 ppm.而GIAO-B3LYP/6-31G*//MMX是一种能兼顾计算时间和计算精度的方法,其RMS、R2和SD分别为4.9、0.996和3.0 4 ppm.  相似文献   

7.
核磁共振波谱实验能够通过谱峰化学位移归属确定化合物分子结构,同时理论计算预测化学位移有助于核磁共振对化合物的谱峰归属. 该文基于李芳等人的核磁共振实验以及分子动力学模拟结果,采用量子化学方法预测了缬沙坦(Valsartan)在SDS胶束中2种构象的化学位移. 通过比较不同量子化学方法和基组的计算结果,特别是采用了ONIOM模型考虑了胶束环境对药物分子化学位移的影响,表明Valsartan在SDS胶束溶液中所存在的2种构象可以通过理论计算加以区分,且这2种构象的化学位移理论预测值与NMR实验值吻合得很好. 本工作表明在计算复杂体系化合物的化学位移时,理论模型应该考虑环境效应的影响.  相似文献   

8.
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,BHand HLYP,M06-2X,CAM-B3LYP和LC-?PBE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(CH13)2SO中的H 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).  相似文献   

9.
碳炔分子红外振动光谱的理论模拟研究   总被引:1,自引:1,他引:0  
卢嘉春 《光谱实验室》2003,20(5):639-642
碳炔分子具有不同的结构,相应的红外谱图具有不同的振动吸收峰位。本文以GAUSSIAN98计算程序在HF水平选用6—31 G(d,p)基组对两种不同结构碳炔的红外光谱进行理论模拟计算。结果表明两种不同结构的碳炔分子的红外振动吸收峰位存在差异,不同共轭碳链长度影响红外吸收峰的峰位和峰强度。计算结果可应用于碳炔材料红外谱图的谱峰归属和分析。  相似文献   

10.
用量子化学从头算(ab initio)方法,在B3LYP/6-31G(d,p)水平上,优化了二苯铬及其衍生物的构型,并进行了振动分析. 3种化合物的振动光谱中均未出现虚频率. 在此基础上,在B3LYP/6-31++G(d,p)水平上,采用GIAO方法,计算了3种化合物的核磁共振碳谱,所得结果与实验值基本吻合.  相似文献   

11.
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.  相似文献   

12.
刘季红  靳焜  王平  罗根 《波谱学杂志》2019,36(3):341-349
七叶亭衍生物含有药效性较高的苯二酚基团,具有各种生物活性.本文以七叶亭(化合物1)为母体,通过将苯基引入到4位、将甲氧基与羟基分别引入到5、6、7和8位,得到一系列七叶亭衍生物2~14.首先以七叶亭为例,以DMSO-d6作为溶剂,采集了它的多种核磁共振(NMR)谱图(包括1H NMR、13C NMR、1H-13C HSQC、1H-13C HMBC),并进行了较详细的化学位移归属;然后对七叶亭衍生物2~141H和13C NMR进行了全归属;另外,讨论了取代基变化对七叶亭及其衍生物上的1H和13C NMR化学位移的影响;最后,使用GIAO和CSGT两种量子化学计算方法计算了七叶亭及其衍生物上的1H和13C NMR化学位移,并与它们的实测值做了比较.  相似文献   

13.
In the present study, structural properties of Mono-(2-Pyridyl) Hydrazone were studied extensively utilizing density functional theory (DFT) employing B3LYP exchange correlation. The Fourier transform infrared (solid phase) was recorded. The vibrational frequencies in the ground state were calculated by using density functional method (B3LYP) with 6-31G* and 6-311G** as basis sets. The spectral studies revealed that the title compound exists in Keto form. Spectral techniques that we employed include 1H and 13C NMR, electronic, thermal techniques. Correlation between experimental chemical shifts and GIAO/B3LYP/6-311G**-calculated isotropic shielding constants, δexp = a + bσcalc, are reported. Good linear regressions between experimental and theoretical results for 1H and 13C were obtained.  相似文献   

14.
1H-, 13C-, and 15N-NMR studies of five nitrobenzene-1,2-diamines in solution and solid state have been achieved and the experimental chemical shifts and coupling constants agree with the theoretical values obtained at the B3LYP/6-311 + +G(dp) computational level using the geometries fully optimized with the hybrid HF/DFT B3LYP method and the 6-31G(d) basis set. The GIAO approximation has been used to calculate the absolute shieldings. The contribution of the substituents to the 15N chemical shifts of the amino groups could be quantified using a presence/absence matrix and a multiple regression.  相似文献   

15.
Geometric optimization and gauge including atomic orbital (GIAO). 1H and 13C NMR chemical shift calculations with Hartree–Fock (HF) method and density functional method (B3LYP), using the 6‐31G(d) and 6‐31+G(d) basis sets, are proposed as a tool to be applied in the structural characterization of ethene‐1,1,2,2‐tetrayltetramethylene tetrathiocyanate, thus providing useful support in the interpretation of experimental NMR data. Parameters related to linear correlation plot of computed versus experimental 13C NMR chemical shifts in DMSO‐d6 are provided.  相似文献   

16.
刘珊  张妹  苏宇  刘权  廖显威 《波谱学杂志》2007,24(2):175-181
在B3LYP/6-31G水平下优化了3种黄酮醇类(山奈酚,槲皮素,杨梅素)化合物的几何构型. 在振动分析中,均未出现虚频率. 在B3LYP/6-31G的水平下计算了该类化合物的核磁共振碳谱. 研究结果表明:3种分子均有分子内氢键形成,且分子内氢键的键长为0.17~0.18 nm左右 . 本文讨论了羟基引入之后对邻近C的化学位移的影响. 从取代基对NMR的影响来看,随着取代基对苯环的供电子能力的加强,取代基邻近的一些C的化学位移有所改变.   相似文献   

17.
The molecular geometry, vibrational frequencies, gauge including atomic orbital (GIAO) 1H and 13C chemical shift values of ABZ-TNB [ABZ-TNB: 2-aminobenzimidazole-trinitrobenzene] and ABZ-PA [ABZ-PA: 2-aminobenzimidazole-picric acid] in the ground state were calculated by using density functionals (B3LYP and PBE1PBE) and Hartree-Fock (HF) methods with the 6–31 ++ G(d,p) basis set. Furthermore, the electronic spectrum of title complexes was calculated with the time dependent DFT levels (TD-PBE1PBE and TD-B3LYP) and HF (TD-HF) method starting from the ground state geometry optimized in the gas phase. A detailed assignment of vibrational spectra was made on the basis of the calculated potential energy distribution (PED). Total static dipole moment (μ), the mean polarizability (〈α〉), the anisotropy of the polarizability (Δα), the mean first-order hyperpolarizability (〈β〉), highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies, chemical hardness (η) and electronegativity (χ) of ABZ-TNB and ABZ-PA complexes were also investigated with quantum chemical calculations. Additionally, data obtained from quantum chemical calculations were compared with the experimental ones.  相似文献   

18.
This study reports the structural characterization of a disulfonimide derivative, 4-methyl-N-(4-methylphenylsulfonyl)-N-phenylbenzenesulfonamide (MPBSA), using spectroscopic and quantum chemical methods. The molecule was characterized with FT-IR, 1H 13C NMR and UV-Vis spectroscopies. Quantum chemical calculations of molecular geometry, vibrational wavenumbers and gauge including atomic orbital (GIAO) 1H and 13C-NMR chemical shifts of the compound were carried out by using density functional method (DFT) at B3LYP/6?311++G(d,p) level of theory. Electronic absorption spectra of the compound have been computed using the time-dependent density functional theory (TD-DFT) method at the same level. A satisfactory consistency between the experimental and theoretical findings was obtained. The antimicrobial activity screening of the compound was performed on some bacteria and fungus species using microdilution method. The results showed that the title molecule have noteworthy antibacterial and antifungal activities.  相似文献   

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