高岭石结构缺陷的 1H MAS NMR和Raman研究

The structure default of kaolinites was characterized with ¹H MAS NMR and Raman spectra. Although the HI indexes of Suzhou and Maoming kaolinite are similar, their ¹H MAS NMR and Raman spectra are very different. ¹H MAS NMR showed that the hydroxyl proton chemical shifts of Suzhou kaolinite are in the higher field and with larger different between the inner surface hydroxyls protons and inner hydroxyls proton chemical shifts than Maoming kaolinite. Raman spectra showed that the surface hydroxyls stretching vibration bands of Suzhou kaolinite are in the high frequency region, and the half height widths of the bands are 7.0～14 cm^-1. The area ratio S_z/(S_z+S_A), where S_Z and S_A are the areas of bands 3685 cm^-1 and 3695 cm^-1 respectively, is 0.23. But the surface hydroxyls stretching vibration bands of Maoming kaolinite are in the low frequency region, and the half height widths of the bands are 8.9～15.1 cm^-1. The area ratio S_z/(S_z+S_A) is 0.77. Those data proved that Suzhou kaolinite has lower structure default than Maoming kaolinite and ¹H MAS NMR and Raman spectra are effective method for study of kaolinite structure default.     

DMA水溶液的1H NMR研究

测量了N，N-二甲基乙酰胺(DMA)水溶液体系不同温度下全浓度范围的^1H NMR数据，对体系中的缔合情况进行了讨论。应用化学缔合模型求得了各缔合平衡常数K和缔合平衡的△H，结合N，N-二甲基甲酰胺(DMF)和N-甲基乙酰胺(NMA)水溶液的研究结果，发现酰胺自身结构和酰胺浓度是影响酰胺水溶液性质的主要因素。     

29Si NMR研究TEOS/DDS双前驱体体系的水解动力学

原位引入有机组分对氧化硅体系改性是合成有机-无机杂化硅材料的重要方法. 利用原位的²⁹Si液体核磁, 研究了甲醇为溶剂、氨水催化条件下的四乙氧基硅烷(TEOS)和二甲基二乙氧基硅烷(DDS)原位共水解的动力学过程. 通过改变反应体系中氨和水的浓度, 拟合出单体及中间产物浓度随时间的变化曲线, 得到了TEOS和DDS各自的水解速率常数以及相应各反应物的反应级数. 与单前驱体水解一致的是, 在双前驱体系中TEOS和DDS自身的反应级数仍保持一级, 但是氨和水的反应级数都有不同程度的增大. 与单前驱体水解速率方程相比, 混合体系中TEOS的水解速率常数增大. 同时, DDS在双前驱体中比单前驱体中的水解速率常数有很大程度的减少. 水解动力学表明, TEOS和DDS在双前驱体体系中显示出更平行的水解速率. 利用固体²⁹Si MAS NMR, XPS及小角X射线散射(SAXS)手段对双前驱体体系研究得到的信息显示, 碱催化条件下原位的TEOS水解中间物与DDS中间产物的原位共缩聚程度很弱.     

Li＋在PC＋DMF混合溶剂中优先溶剂化的13C NMR研究

利用¹³C NMR光谱技术研究了Li^＋在碳酸丙烯酯(PC)＋N,N-二甲基甲酰胺(DMF)混合溶剂中的优先溶剂化现象. 根据溶剂分子中碳原子的化学位移随锂盐浓度的变化关系, 确定了与Li^＋发生配位的原子. 碳原子的配位位移值随混合溶剂组成的变化关系表明, 在LiClO₄＋PC＋DMF混合物中, DMF分子对Li^＋的溶剂化作用较PC分子强. 定量计算得到, 在n(PC)∶n(DMF)＝1∶1(摩尔比)的混合溶剂中, PC与DMF分子数在Li^＋第一溶剂化层中的比率为0.12, 说明Li^＋优先被DMF分子溶剂化.     

Li＋在PC＋DMF混合溶剂中优先溶剂化的13C NMR研究

利用¹³C NMR光谱技术研究了Li^＋在碳酸丙烯酯(PC)＋N,N-二甲基甲酰胺(DMF)混合溶剂中的优先溶剂化现象. 根据溶剂分子中碳原子的化学位移随锂盐浓度的变化关系, 确定了与Li^＋发生配位的原子. 碳原子的配位位移值随混合溶剂组成的变化关系表明, 在LiClO₄＋PC＋DMF混合物中, DMF分子对Li^＋的溶剂化作用较PC分子强. 定量计算得到, 在n(PC)∶n(DMF)＝1∶1(摩尔比)的混合溶剂中, PC与DMF分子数在Li^＋第一溶剂化层中的比率为0.12, 说明Li^＋优先被DMF分子溶剂化.     

31P MAS NMR固体核磁共振研究稀土改性Y分子筛的酸性

以三甲基磷氧（TMPO）和三丁基磷氧（TBPO）为探针分子,用³¹P魔角旋转核磁共振（³¹P MAS NMR）法对稀土改性Y型分子筛的酸性进行了定性和定量分析. 结果表明,以TMPO为探针分子的³¹P MAS NMR谱分别在δ = 78,70,65,62,58,55和53处存在与酸中心相关的吸收峰,其中δ = 78和70处吸收峰与分子筛内部和外部酸性有关,δ = 65,62,58和53处吸收峰归属于TMPO在分子筛内部Brönsted酸中心上的贡献,δ = 55处吸收峰归属于TMPO在分子筛内部Lewis酸中心上的贡献. 随着稀土含量的增加,中等强度Brönsted酸中心（δ = 62和58）数量显著增加,而强Brönsted酸中心（δ = 65）和较弱Lewis酸中心（δ = 55）数量显著降低. 结合分子筛骨架铝和非骨架铝对分子筛酸性的影响进一步探讨了稀土改型Y分子筛的酸性.     

Rh/SiO2催化剂上氢物种的1H MAS NMR研究

采用¹H MAS NMR技术,分别对不同温度(773和973 K)、不同气氛(氢气、氧气、氦气及空气)条件下处理的SiO₂和Rh/SiO₂催化剂上的氢物种和含氢物种进行了研究.在SiO₂及经氧气处理的催化剂上,检测到了位于约7.0,3.8~4.0,2.0及1.0~1.5处的一系列信号,它们可分别归属为强吸附H₂O,物理吸附H₂O,SiOH及受SiO₂晶格氧缺陷位屏蔽影响的SiOH.而在经氢气处理的催化剂上,除了上述诸信号外,还检测到了位于3.0和0.0处的低场信号及约位于-110处的高场信号.其中,低场信号分别归属为弱吸附在载体SiO₂中的桥式晶格氧处的氢物种(溢流氢物种)和晶格氧缺陷处的氢物种(Si-H物种),而高场信号则同时归属为解离吸附在Rh上的可逆吸附氢物种和不可逆吸附氢物种.经氢气处理的催化剂上,可能还形成了另外一种以独特的“离域氢”形式存在于Rh上的解离吸附氢物种(b氢物种). 该氢物种应具有-20~-50的化学位移,但其信号因被低场信号的自旋边带掩盖而未能在1H MAS NMR实验中直接观察到.溢流氢物种和Si-H物种由可逆吸附氢物种和/或b氢物种从Rh上向邻近的载体SiO₂迁移而形成.高温对于氢溢流过程更为有利.     

人宫颈癌细胞(Hela)内的31P核磁共振研究

建立了无损伤性³¹P NMR研究细胞内物质的实验方法, 并对人宫颈癌细胞(Hela)的³¹P NMR谱中含磷小分子代谢物的谱峰进行了分析; 细胞内无机磷(Pi)的化学位移对pH非常敏感, 通过测定其化学位移可间接确定细胞内的pH, Hela细胞内Pi峰的化学位移为5.88±0.01 (n＝3), 计算得到细胞内 pH值为7.05±0.01; 通过测量Hela细胞的³¹P NMR谱中ATP的α磷和β磷及γ磷的化学位移差值, 得出Hela细胞内Mg^2＋与ATP结合的复合物MgATP和整个ATP量的比值, 计算得到Hela细胞内游离Mg^2＋浓度为(253.3±0.13) mmol/L (n＝3), 与其它分析方法相比, ³¹P NMR测定细胞内游离Mg^2＋浓度具有对细胞样品无损伤的优点.     

人宫颈癌细胞(Hela)内的31P核磁共振研究

建立了无损伤性³¹P NMR研究细胞内物质的实验方法, 并对人宫颈癌细胞(Hela)的³¹P NMR谱中含磷小分子代谢物的谱峰进行了分析; 细胞内无机磷(Pi)的化学位移对pH非常敏感, 通过测定其化学位移可间接确定细胞内的pH, Hela细胞内Pi峰的化学位移为5.88±0.01 (n＝3), 计算得到细胞内 pH值为7.05±0.01; 通过测量Hela细胞的³¹P NMR谱中ATP的α磷和β磷及γ磷的化学位移差值, 得出Hela细胞内Mg^2＋与ATP结合的复合物MgATP和整个ATP量的比值, 计算得到Hela细胞内游离Mg^2＋浓度为(253.3±0.13) mmol/L (n＝3), 与其它分析方法相比, ³¹P NMR测定细胞内游离Mg^2＋浓度具有对细胞样品无损伤的优点.     

D-苯丙氨酸与Cu＋(1S0, 3d10)气相反应理论研究

用量子化学密度泛函(DFT)方法研究D-苯丙氨酸与一价基态金属阳离子Cu^＋在气相中反应的机理. 在B3LYP/6-31G*水平上, 优化了反应包含的4个反应通道的反应物、中间体、过渡态和产物的几何构型, 并采用B3LYP/DZVP, B3LYP/[6-311＋G**(C,H,O)＋Lanl2dz(Cu)], B3LYP/6-311＋G**, MP2/6-311＋G** 等方法对各驻点进行了单点能计算. 通过对计算结果的分析, 获得了其单重态反应势能面的一般轮廓、各驻点几何构型优化参数, 明确了其反应机理.     

顺磁性镧系金属有机配合物的1H核磁共振研究

顺磁类的核磁共振研究大多是简单化合物,偏重理论方面的研究,对镧系配合物曾有报道。由于这类样品对空气和湿气极为敏感,在国内外研究顺磁性¹H谱甚少。本文研究了含氯桥的醚基取代环戊二烯镧系配合物二聚体的¹H化学位移,线宽,弛豫时间T₁和磁化率,从中找出了顺磁类有机镧系配合物¹H NMR的规律。     

DFT和热力学研究氢键协同效应及对关联1H NMR的影响

用DFT方法在B3LYP/6-311＋＋G (d,p)水平下研究了甲醇线性和环状分子簇. 对于不同大小的分子簇之间定义了协同因子. 计算得到的协同因子可以验证氢键的强协同效应, 环状分子簇之间的协同效应远远大于线性分子簇. 做为理论验证和比较, 热力学模型分别采用含氢键缔合的格子流体状态方程(LFHB), 以及含氢键协同效应的LFHB, 关联醇-惰性体系的¹H核磁共振化学位移. 考虑协同效应的关联结果优于原始的LFHB. 比较量子化学计算的和热力学模型中采用的协同因子, 认为甲醇和乙醇在溶液中更可能大部分以线性缔合形式存在.     

1H MAS NMR characterization of hydrogen over silica-supported rhodium catalyst

Hydrogen species in both SiO₂ and Rh/SiO₂catalysts pretreated in different atmospheres (H₂, O₂, helium or air) at different temperatures (773 or 973 K) were investigated by means of¹H MAS NMR. In SiO₂ and O₂-pretreated catalysts, a series of downfield signals at ∼7.0, 3.8–4.0, 2.0 and 1.5–1.0 were detected. The first two signals can be attributed to strongly adsorbed and physisorbed water and the others to terminal silanol (SiOH) and SiOH under the screening of oxygen vacancies in SiO₂lattice, respectively. Besides the above signals, both upfield signal at ∼−110 and downfield signals at 3.0 and 0.0 were also detected in H₂-pretreated catalyst, respectively. The upfield signal at ∼−110 originated from the dissociative adsorption of H₂ over rhodium and was found to consist of both the contributions of reversible and irreversible hydrogen. There also probably existed another dissociatively adsorbed hydrogen over rhodium, which was known to be β hydrogen and in a unique form of “delocalized hydrogen”. It was presumed that the β hydrogen had an upfield shift of ca. −20–−50, though its¹H NMR signals, which, having been masked by the spinning sidebands of Si-OH, failed to be directly detected out. The downfield signal at 3.0 was assigned to spillover hydrogen weakly bound by the bridge oxygen of SiO₂. Another downfield signal at 0.0 was assigned to hydrogen held in the oxygen vacancies of SiO₂ (Si-H species), suffering from the screening of trapped electrons. Both the spillover hydrogen and the Si-H resulted from the migration of the reversible hydrogen and the β hydrogen from rhodium to SiO₂ in the close vicinity. It was proved that the above migration of hydrogen was preferred to occur at higher temperature than at lower temperature.     

1H mas NMR study of OH groups in the AlPO4/SiO2 system

Three solids of composition SiO₂, AlPO₄ and 20∶80 mol/mol AlPO₄/SiO₂, respectively, were synthesized. Their textural properties were examined and¹H MAS NMR spectroscopy was used to characterize their surface OH groups. The results reveal that the solids are amorphous and texturally suitable for use as catalysts.     

2H Chemical-shift resolution and dipolar2H-1H,2H-15N correlations in solid-state MAS NMR spectroscopy for structure determination and distance measurements in hydrogen-bonded systems

In solid-state NMR, deuteron (²H) spectroscopy can be performed in full analogy to¹H spectroscopy, including²H chemical-shift resolution and²H-X dipolar correlation schemes, when the NMR experiments are conducted in a “rotor-synchronized” fashion under fast magic-angle spinning. Here, 2H-X NMR experiments of this type, including²H-¹⁵N and²H-¹H chemical-shift correlations and distance measurements, are introduced and demonstrated on cytosine monohydrate, whose acidic protons can readily be replaced by deuterons by recrystallization from D₂O. In this way,²H NMR spectroscopy provides information complementary to¹H NMR data, which is particularly useful for studying hydrogen bonds in supra- or biomolecular systems. Electronic supplementary material Supplementary material is available in the online versionof this article atand is accessible for authorized users.     

核磁共振研究二茂铁硒铂配合物构象交换热焓

The intramolecular conformational exchange thermodynamics of cis-PtCl[1,1'bis(undecenylseleno)ferrocene](B11SeFcPt) in CDCl3 solution was studied by one dimensional proton NMR． The chemical equilibrium constants were obtained directly from the integration of the 1H NMR spectra and the enthalpy as a function of temperature for the conformational exchange of B11SeFcPt was calculated from the equilibrium constant.     

对位取代四苯基卟啉及其铁(Ⅲ)配合物的~1H NMR研究

本文用BRUKER MSL-400型超导核磁共振仪,对于对位取代四苯基卟啉[H_2(p-X)TPP,X=Cl,H,CH_3,OCH_3],对位取代四苯基卟啉铁(Fe(Ⅲ)(p-X)TPPCl)及其轴向配合物([Fe(Ⅲ)(p-X)TPP(HIm)_2]~+Cl~-,([Fe(Ⅲ)(p-CH_3)TPPYm]~+Cl~-,Y=2-CH_3Im,2-C_2H_5-4-CH_3Im,n-C_3H_7NH_2,N(C_2H_5)_3)的质子核磁共振谱进行了较系统的研究,探讨了分子对称性、电子结构、顺磁效应等对~1H NMR谱的影响以及铁卟啉配合物的电子自旋离域机理。     

核磁共振氢谱中卫星峰在教学科研中的应用*

系统介绍了核磁共振氢谱中卫星峰的种类、组成和分析方法。卫星峰中包含了大量的低丰度自旋核和氢核,特别是13C-1H间的精细偶合信息。这些偶合中1J偶合最为常见,该偶合常数和C-H之间的化学环境息息相连。因此,若能把握这类信息,对于结构解析是很大一个助力。本文详细介绍了几例卫星峰的分析过程及其在大学化学课程教学和科研中的应用,特别是用于理解超共轭效应和立体电子效应。