晶体学辅助的2-吡啶甲酸固体~(13)C化学位移理论计算归属（英文）

有机分子的互变异构现象在溶液中较为常见.而对于有机固体而言,存在互变异构可能的分子常以单一的能量最稳定的异构体形式存在. 2-吡啶甲酸(PCA)是一个较为罕见的案例,它的晶体结构中同时存在有中性分子和两性离子两种互变异构体.由于超长的质子纵向弛豫时间,PCA的固体~(13)C核磁共振(NMR)实验的化学位移归属存在困难.密度泛函理论(DFT)计算,特别是基于周期性模型的方式是一种可以准确快捷归属其化学位移的方案.然而,由于PCA结构中活泼质子的占位无序,其结构并不能直接或经简单处理后递交计算.本文中,我们通过晶体学手段构建了一个虚拟晶体结构.基于该虚拟结构的~(13)C化学位移计算值可与实验值准确吻合.此外,不同互变异构状态的PCA表现出不同的特征化学位移,这一信息可被用来分析PCA在其晶体复合物中的分子状态.     

高分子化学位移的量化计算与固体NMR实验研究

该文以2种不同立构聚丙烯（iPP和sPP）为讨论对象,首先研究了量化计算方法在预测高分子¹³C 各向同性和各向异性化学位移（CSA）中的应用,然后讨论了近年来发展的测定¹³C CSA粉末线形的2种重要固体NMR实验技术（SUPER和RAI）的特点和实验优化问题. 最后,利用可获得接近无扭曲线形的SUPER技术测定了等规立构聚丙烯样品的¹³C CSA粉末线形,并与量化计算理论结果比较. 结果表明：¹³C 各向同性化学位移及CSA粉末线形的理论计算结果均与固体NMR实验结果有很好的符合,预示通过¹³C CSA量化计算结合固体NMR实验是阐明高分子微观结构的有力工具.     

α,α'-二氧代烯酮环二硫代缩酮的NMR研究

报道标题化合物的NMR谱,利用¹H,¹³C NMR和DEPT等技术确定新化合物的化学结构,并归属了所有质子和碳的化学位移.     

固体丁酸类代谢物13C化学位移的结构依赖性

丁酸类代谢物广泛存在于动物、植物和微生物中,且具有多种重要的生理功能,但它们的固体核磁共振参数、分子动力学性质及其结构依赖性并未得到清楚的认识. 该文使用高分辨交叉极化与魔角旋转核磁共振（¹³C CPMAS）实验技术,分析了一系列固体丁酸类代谢物的¹³C化学位移, 发现了这些代谢物的¹³C化学位移与其分子结构的一些相关性规律. 另外还发现,固体丁酸类代谢物与其在溶液中的¹³C化学位移有显著的差异. 这些代谢物中甲基参与的疏水作用以及羟基、氨基和羧基参与的氢键作用均对其化学位移大小有重要的影响. 上述结果为认识代谢物的结构和功能以及功能对结构的依赖性提供了重要信息.     

核磁共振研究大叶蛇葡萄提取物蛇葡萄素

通过质子检测的¹³C-¹H异核多键化学位移相关谱、¹³C-¹H异核多量子化学位移相关谱和质子相敏交换谱等NMR二维方法确定了传统中草药大叶蛇葡萄提取物的结构为蛇葡萄素(3,3',4',5,5',7-六羟基双氢黄酮醇),得到了更加准确的¹H和¹³C化学位移归属,并观测和讨论了这一体系中溶剂二甲亚砜的质子化现象.     

Manumycin的2D NMR研究

应用1D NMR 和梯度2D NMR技术（gCOSY，gNOESY，gHSQC，gHMBC）深入研究了从链霉菌发酵物中分离提取得到的Manumycin的结构，并对其¹H和¹³C NMR化学位移进行了全归属. 计算机分子模拟与NMR研究取得一致结论.     

七叶亭及其衍生物的NMR研究

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2~14的¹H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.     

苯基哌嗪衍生物的NMR波谱研究

通过¹H NMR、¹³C NMR、及HMBC、HSQC、¹H-¹H DQFCOSY等2D NMR方法对新合成的10个苯基哌嗪衍生物类抗高血压药物进行结构鉴定, 并对这些化合物的¹H NMR和¹³C NMR信号进行了全归属. 初步探讨了取代基对分子¹³C化学位移的影响.      

癌基因MDM2阻断剂的分子结构的NMR研究

根据P53-MDM2复合物晶体结构,设计合成了非肽类小分子作为MDM2的阻断剂.利用超导核磁共振波谱仪,测定了化合物的¹H谱、¹³C谱、¹H-¹H COSY谱、HMQC和HMBC谱,确定了化合物的结构,归属了化合物的¹H、¹³C化学位移,为筛选抗癌活性化合物提供了理论依据.     

开链烷烃13C化学位移统计分析

将开链烷烃的¹³C化学位移与分子中¹³C核邻近原子上的电子集居数及¹³C原子的局部空间能相关联,对14个典型烷烃分子中的72个碳原子的数据用逐步回归方法进行处理,所得结果表明:¹³C化学位移与上述诸因子间存在明显的线性关系.72个碳原子的¹³C化学位移预报值的均方根偏差为0.835ppm,最大偏差为2.232ppm.     

An ab initio calculation of 17O and 29Si NMR parameters for SiO2 polymorphs

Ab initio molecular orbital calculations (Hartree–Fock, HF and density functional theories, DFTs) have been carried out for SiO₂ polymorphs coesite, low cristobalite, and -quartz, in order to investigate the reliability of this method for predicting ²⁹Si and ¹⁷O nuclear magnetic resonance (NMR) properties of silicates. Oxygen- and silicon-centered clusters consisting of one (1T) to three tetrahedral (3T) shells (one to four atomic shells), taken from real crystal structure, have been investigated. It is found that for reasonable predication of both the ²⁹Si and ¹⁷O chemical shifts (δ_i^Si and δ_i^O), the minimum cluster is one that gives the correct second neighbors to the nucleus of interest. Both the δ_i^Si and δ_i^O have reached convergence with respect to cluster size at the OH-terminated two tetrahedral (2T) shell (three atomic shells around Si and four atomic shells around O) model. At convergence, the calculated δ_i^Si values agree well (within ±1 ppm) with experimental data. The calculated ¹⁷O electric field gradient (EFG)-related parameters also agree with experimental data within experimental uncertainties. The calculation also reproduces small differences in δ_i^O for O sites with similar tetrahedral connectivities, but shows deviations up to about 10 ppm in relative difference for O sites with different tetrahedral connectivities. The poor performance for the latter is mainly due to the approximations of the HF method. Our study thus suggests that the ab initio calculation method is a reliable mean for predicting ²⁹Si and ¹⁷O NMR parameters for silicates. Such an approach should find application not only to well-ordered crystalline phases, but also to disordered materials, by combining with other techniques, such as the molecular dynamics simulation method.     

On reasons of Si NMR chemical shift/structure relations for silicon oxides, nitrides, and carbides: An individual-gauge-for-localized-orbitals study

For -quartz, monoclinic ZSM-5, -and β-Si₃N₄ and SiC---6H polytype, the silicon chemical shifts have been calculated using the IGLO (individual gauge for localized orbitals) method and models of different size in real crystal geometry. The result is a theoretical chemical shift scale, which is very similar to the corresponding experimental scale from ²⁹Si MAS NMR experiments. It is shown that the assignment of isotropic silicon chemical shifts of crystallized solids based on theory is a method of practical applicability, also in cases where experimental methods or empirical relations fail. The two NMR spectral lines of -Si₃N₄ are for the first time assigned to the crystallographic positions. The partition of the silicon chemical shifts into localized contributions from different parts of the model allows insight into the interactions around the resonance nucleus due to substituent and geometry variations leading to silicon chemical shifts.     

双环磷酸酯类化合物NMR结构效应研究

用现有理论说明不了双环磷酸酯类化合物³¹P NMR化学位移的变化。本文在我们提出的核外电子云球对称效应原理基础上,用量子化学和分子力学计算的参数,表达了这类化合物³¹P化学位移变化的规律,同时还研究了它们的¹³C NMR化学位移和偶合常数的取代基效应。     

FPT-CNDO/INDO化学屏蔽常数计算方法及其在Mo和Co化合物中的应用

Semi -empirical molecular orbital methods within the framework of the finite perturbation theory , the FPT-CNDO/INDO methods , which consist of the FPT-CNDO/2 and FPT-INDO methods, are set up for the study of chemical shielding in transition metal compounds, and a corresponding computational program is developed on VAX 11/785 computer to establish a theoretical study of the transition metal chemical shielding by quantum chemistry methods. Application of the methods has been carried out in the calculation of 95Mo chemical shielding constants of mononuclear precursors [MoOnS4-n]2-(n=0-4). With the standard CNDO/INDO parameters a linear regression was obtained between the calculated results and the corresponding experimental data:δcal=(0.8345 δexp-43.83)ppm, with a correlation coefficient of 0.999. Investigation on the calculated electronic configuration confirms that in [MoOnS4_n]2- (n=0-4)95Mo chemical shifts are dominated by the d-orbital paramagnetic contribution arising from the d-d transition. Appl     

6-(4-氯苯氧基)四唑并[5,1-a]酞嗪的核磁共振谱峰归属

为确保具有独立知识产权的国家级一类抗癫痫创新候选药物的药品安全，采用500 MHz核磁共振（NMR）技术，结合规范不变原子轨道-核磁共振（GIAO-NMR）量子化学计算方法，对进入临床阶段的抗癫痫药6-（4-氯苯氧基）四唑并[5，1-a]酞嗪的¹H NMR、¹³C NMR和¹⁵N NMR信号进行了归属，从而为安全用药提供了精确结构信息．线性回归对比表明，标度法计算的NMR化学位移与实验值吻合较好．     

Modeling NMR chemical shifts: a comparison of charge models for solid state effects on N chemical shift tensors

This paper presents results from applying different point charge models to take into account intermolecular interactions to model the solid state effects on the ¹⁵N NMR chemical shifts tensors. The DFT approach with the BLYP gradient corrected exchange correlation functional has been used because it can include electron correlation effects at a reasonable cost and is able to reproduce ¹⁵N NMR chemical shifts with reasonable accuracy. The results obtained with the point charge models are compared with the experimental data and with results obtained using the cluster model, which includes explicitly neighboring molecular fragments. The results show that the point charge models can take into account solid state effects at a cost much lower than the cluster methods.     

七-O-乙酰基-β-麦芽糖基羧酸酯的NMR研究

通过对6种七-O-乙酰基-β-麦芽糖基羧酸酯的¹H NMR和IR谱的分析, 确证其糖苷键为β-构型, 对其一般特征进行了对比和讨论, 用¹H-¹H COSY, gHMQC, gHMBC等技术对它们的¹H和¹³C NMR谱峰进行了全归属.     

α-萘乙酸芳酯的13C NMR研究

报道了7种新的α-萘乙酸芳酯的¹³C NMR谱.对其全部谱峰进行了归属,并讨论了化学位移与分子结构间的一些关系。     

NMR探针分子表征分子筛酸性的理论研究

用量子化学计算的方法,采用三甲基氧膦（TMPO）、吡啶和三甲基膦（TMP）3种探针分子,研究了工业上常用的3种分子筛H-Y、H-ZSM5、H-MOR的Bronsted酸强度,讨论了这3种探针分子化学位移与Bronsted相对酸强度的相关性,揭示了各种探针分子在表征Bronsted酸性上的适用性.