NMR study of solid C60(γ-cyclodextrin)2

A solid complex of C₆₀ with γ-cyclodextrin (γ-CyD) was examined with NMR spectroscopic methods in order to understand the dynamics of C₆₀, and the interaction between C₆₀ and γ-CyD. A ¹³C solid-state cross-polarization magic angle spinning (CP/MAS) NMR spectra shows C₆₀ resonance at 142.6 ppm. This provides the evidence of interaction between ¹³C spins in C₆₀ and ¹H spins in the γ-CyD host. Ambient temperature experiments on the ¹³C CP/MAS NMR, with varying contact time, shows that the water associated with γ-CyDs plays an important role in the nuclear relaxation processes. The dynamics of C₆₀ in γ-CyD was investigated using temperature and field-dependent ¹³C spin-lattice relaxation time measurements. The influence of water on the dynamics of C₆₀ was less significant below 250 K.     

Characterization of polyalkylvinyl ether phases by solid-state and suspended-state nuclear magnetic resonance investigations

Pure organic polyalkylvinyl ether phases were synthesized by suspension polymerization using different ratios and compositions of n-butylvinyl ether (C₄VE) and n-octadecylvinyl ether (C₁₈VE) with triethylene glycol divinyl ether or divinylbenzene as crosslinkers, respectively. These phases were investigated by means of solid-state ¹³C cross-polarization magic angle spinning nuclear magnetic resonance (NMR) spectroscopy and ¹H high-resolution magic angle spinning (HR MAS) NMR spectroscopy in suspended-state. A comparison of these two methods showed the substantial advantages of ¹H HR MAS NMR measurements. Structure elucidation was achieved using a 2D H,H-COSY NMR experiment performed under MAS conditions enabling full peak assignment of the ¹H NMR spectra of these phases. The dynamic behavior of the polyalkylvinyl ether phases was determined by employing temperature-dependent measurements of spin–lattice relaxation times (T₁) as well as accumulation of a 2D wide line separation NMR spectrum.     

镜煤吡啶不溶物及其热解加氢产物的NMR研究

本文对镜煤吡啶不溶物、热解加氢后吡啶及四氢呋喃不溶物进行了固体NMR研究,获得了12种结构参数,并对热解加氢产物中的苯可溶各馏份进行了一维、二维液体NMR研究,归属了其¹³C和¹H谱,计算了各馏份的平均分子结构.     

Unusual observation of nitrogen chemical shift anisotropies in tetraalkylammonium halides by 14N MAS NMR spectroscopy

¹⁴N Magic-angle spinning (MAS) NMR spectra for a number of polycrystalline, symmetrical tetraalkylammonium halides with short alkyl chains (C₂H₅– to n-C₄H₉–) have been recorded following a careful setup of the experimental conditions. Analysis of the spectra demonstrates the presence of ¹⁴N chemical shift anisotropies (CSAs) on the order of |δ_σ|=10–30 ppm along with ¹⁴N quadrupole coupling constants in the range of 10–70 kHz. The magnitude and sign of the CSAs determined from ¹⁴N MAS NMR are confirmed by recording and analysis of the corresponding slow-speed spinning (500–650 Hz) ¹⁵N CP/MAS NMR spectra. Most interestingly, it is observed experimentally and demonstrated theoretically and by simulations, that these CSAs are reflected in the spinning sideband (ssb) intensities of the ¹⁴N MAS spectra at much higher spinning speeds than can be applied to retrieve the corresponding ¹⁵N CSAs from the ssb pattern in the ¹⁵N CP/MAS spectra.     

The surface structure of catalysts activated with hydrogen donors as elucidated by multinuclear solid-state NMR

¹H, ²⁷Al and ³¹P MAS, and ¹³C and ²⁹Si CP/MAS NMR spectroscopies, were used to characterize catalysts of Pd supported on various solids including SiO₂, AlPO₄ and Mg₃(PO₄)₂ that were activated with the chiral hydrogen-donor limonene. The above-mentioned techniques were used to check for the formation of an organopalladium complex between Pd²⁺ atoms and the olefin bonds in the limonene molecule on the catalyst surface. The results are compared with those obtained for catalysts activated in a hydrogen stream.     

取代基的电子效应对苯甲酰苯胺衍生物NMR化学位移的影响

用400MHz超导核磁共振波谱仪测定了X取代苯甲酰苯胺(X=p-NO₂,p-Cl,p-Br,p-1,H,p-CH₃,p-OCH₃,m-CH₃)的¹H和¹³C NMR谱,按双参数方程进行计算,结果表明N-¹H,羰基碳,与羰基相连的苯环碳和与氮相连的苯环碳等碳原子的化学位移与取代基共轭效应参数σ_R和诱导效应参数σ_I间的良好的线性关系。测得了双参数方程中适用于苯甲酰苯胺衍生物的3个常数a、b和c的值以及σ_R、σ_I的权重。     

取代基的电子效应对苯甲酰苯胺衍生物NMR化学位移的影响

用400MHz超导核磁共振波谱仪测定了X取代苯甲酰苯胺(X=p-NO₂,p-Cl,p-Br,p-1,H,p-CH₃,p-OCH₃,m-CH₃)的¹H和¹³C NMR谱,按双参数方程进行计算,结果表明N-¹H,羰基碳,与羰基相连的苯环碳和与氮相连的苯环碳等碳原子的化学位移与取代基共轭效应参数σ_R和诱导效应参数σ_I间的良好的线性关系。测得了双参数方程中适用于苯甲酰苯胺衍生物的3个常数a、b和c的值以及σ_R、σ_I的权重。     

取代基效应(SCS)与乙烯-α-烯烃共聚物的序列结构——7.氢化丁苯共聚物(HBS)

测定了两个氢化丁苯共聚物样品的¹H、¹³C NMR谱。通过处理文献中的¹³C NMR谱数据得到了-C₂H₅和-C₆H₅的SCS参数。利用乙烯-α-烯烃共聚物的SCS方法结合DEPT NMR实验技术重新归属了该共聚物的¹³C NMR谱。明确指出,氢化丁苯共聚物分子链中主链任何一个乙烯单元的两个CH₂在序列分布上分属于二元组和三元组。CH则用三元组来表征。最后,对HBS共聚物的序列分布进行了计算。     

Solid-state 13C and 1H spin diffusion NMR analyses of the microfibril structure for bacterial cellulose

To obtain further information about the cause for the rather large splitting of the C4 resonance line into the downfield (C4D) and upfield (C4U) lines in CP/MAS ¹³C NMR spectra for native cellulose, ¹³C and ¹H spin diffusion measurements have been conducted by using different types of bacterial cellulose samples. In ¹³C spin diffusion measurements, the C4D resonance line is selectively inverted by the Dante π pulse sequence and the ¹³C spin diffusion is allowed to proceed from the C4D carbons to other carbons including the C4U carbons with use of the ¹³C4-enriched bacterial cellulose sample. The analysis based on the simple spin diffusion theory for the process experimentally observed reveals that the C4U carbons may be located at distances less than about 1 nm from the C4D carbons. In ¹H spin diffusion measurements, poly(vinyl alcohol) (PVA) films in which ribbon assemblies of bacterial cellulose are dispersed are employed and the ¹H spin diffusion process is examined from the water-swollen PVA continuous phase to the dispersed ribbon assemblies by the ¹³C detection through the ¹H–¹³C CP technique. As a result, it is found that the C4D and C4U carbons are almost equally subjected to the ¹H spin diffusion from the PVA phase, indicating that the C4U carbons are not localized in some limited area, e.g. in the surfacial region, but are distributed in the whole area in the microfibrils. These experimental results suggest that the C4U carbons may exist as structural defects probably due to conformational irregularity associated with disordered hydrogen bonding of the CH₂OH groups in the microfibrils.     

H-SAPO-34分子筛催化醇类转化的差异性研究

本文研究了H-SAPO-34催化甲醇和丁醇转化反应及其产物分布的差异,结合气相色谱-质谱（GC-MS）联用、¹³C交叉极化魔角旋转核磁共振（¹³C CP MAS NMR）技术捕获了反应过程中生成的重要反应中间物种.甲醇转化过程以乙烯、丙烯和丁烯为主要产物;而丁醇转化过程中主要产物是丁醇脱水生成的丁烯,反应初期以丙烯和丁烯作为主要产物.两种醇类转化均以低碳烯烃作为主要产物,且存留物种和¹³C CP MAS NMR分析均观察到芳烃物种,说明H-SAPO-34催化甲醇和丁醇转化存留在催化剂上的有机物种相近.虽然起始于不同的醇类反应,但H-SAPO-34上限域空间的酸催化环境都能引导甲醇和丁醇制取低碳烯烃的反应过程.