Structural and dynamical studies of poly(vinyl alcohol) gels by high-resolution solid-state C NMR spectroscopy

The ¹³C CP/MAS NMR spectra of isotactic, syndiotactic and atactic poly(vinyl alcohol) (PVA) gels were measured in order to clarify the structure of the immobile component of PVA gel. In the ¹³C CP/MAS NMR spectra, the three CH carbon peaks I, II and III (at about 77, 71 and 65 ppm) were clearly observed, which originate from the formation of strong intermolecular or intramolecular hydrogen bonds between hydroxyl groups like solid PVA. It has been assigned that these peaks originate from the crosslinked region in the gel state. On the basis of the experimental results, intermolecular hydrogen bonds play an important role in the formation of the crosslinked-region in the gel state. Further, the effect of PVA's tacticity on the amount of the crosslinked regions by intermolecular interactions was discussed. In addition, molecular motion in the immobile and mobile region of PVA gel was discussed through the observation of ¹³C spin-lattice relaxation time T₁.     

部分还原二氧化钛的NMR和EPR研究

Partially reduced TiO₂ nanomaterials have attracted significant interest because of their visible-light activity for catalysis and photodegradation. Herein, we prepared a partially reduced anatase TiO₂ (Re-A-TiO₂) nanoparticle material using a fast combustion method, demonstrating good activity toward decomposing methyl orange under visible light irradiation. The surface structure of the prepared material, after being surface-selectively ¹⁷O-labeled with H₂¹⁷O (¹⁷O-enriched water), was studied via ¹⁷O and ¹H solid-state magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy and electron paramagnetic resonance (EPR) spectroscopy, and the obtained results were compared to those of non-reduced anatase TiO₂ (A-TiO₂). The EPR results showed that the concentrations of paramagnetic species (i.e., oxygen vacancies (OV) and Ti³⁺) in Re-A-TiO₂ were much higher than that in A-TiO₂, while the former was associated with a higher OV/Ti³⁺ ratio. The intensities of the EPR signals were significantly affected by the adsorbed water, and this phenomenon was explored in combination with ¹H NMR spectroscopy. The ¹H species on Re-A-TiO₂ appeared at larger chemical shifts, denoting the increased acidity of the sample, and these ¹H species on Re-A-TiO₂ were more difficult to remove than those on A-TiO₂. On the other hand, different features were observed for the signals arising from the two-coordinated oxygen atoms (μ₂-O) in ¹⁷O NMR, suggesting a typical anatase TiO₂(101) surface on A-TiO₂, but a more complex surface environment for Re-A-TiO₂. Furthermore, a larger amount of hydroxyl groups (OH) were observed on Re-A-TiO₂ compared to that on A-TiO₂, indicating a larger proportion of exposed (001) facets on Re-A-TiO₂. However, the μ₂-O signals broadened and became similar when the drying temperature was increased to 100 ℃, indicating a non-faceted anatase TiO₂ surface in such conditions. Based on the EPR and NMR results, a significant fraction of the OH species is believed to be formed from the reaction of the paramagnetic centers and adsorbed water molecules. The ¹H→¹⁷O cross polarization (CP) MAS and two-dimensional heteronuclear correlation (2D HETCOR) NMR spectra were used to verify the spatial proximity of the hydrogen and oxygen species, confirming the spectral assignments of a strongly adsorbed water and one type of surface OH species. In particular, the ¹H NMR signals at approximately 11 ppm were ascribed to the hydrogen species in the intramolecular hydrogen bond. In summary, this study investigated the paramagnetic species and surface structure of anatase TiO₂ materials by combining EPR along with ¹H and ¹⁷O solid-state NMR spectroscopy. The differences in the surface structures of Re-A-TiO₂ and A-TiO₂ should be closely related to their different properties toward the photodegradation of methyl orange.     

The N and C solid state NMR study of intramolecular hydrogen bond in some Schiff bases

In present work set of eight Schiff bases derived from substituted salicylaldehydes and aliphatic and aromatic amines has been studied in the solid state by ¹⁵N and ¹³C CPMAS NMR methods. ¹⁵N CPMAS NMR measurement is especially useful for investigation of the tautomerism in the compounds considered, owing to the large difference in the nitrogen chemical shifts of OH and NH tautomers. In the solid state, four of the compounds examined were shown by ¹⁵N CPMAS NMR to exist as OH tautomeric forms, and the remaining four as the corresponding NH forms with different stage of proton transfer process, from oxygen to nitrogen site.

This was confirmed by ¹³C CPMAS. The results reported were compared with those obtained for only two compounds in CDCl₃ solutions (solubility problems).     

Wide-line H NMR: a new application for the study of Brönsted acidity strength of solids with HY zeolite as example

The fitting of 4 K ¹H wide-line NMR spectra of Brönsted-acidic solid samples loaded with known amounts of water allows the determination of the concentration of the following species: H₃O⁺, H₂O…HO; and of the remaining initial species: OH and H₂O.     

1,3-丙二胺邻苯二酚钼钨手性八面体配合物的仿生合成、晶体结构以及与ATP作用的液相NMR研究

合成了1,3-丙二胺邻苯二酚钼钨手性八面体配合物(NH₃CH₂CH₂CH₂NH₂)₂[Mo_0.4W_0.6O₂(C₆H₄O₂)₂],并对其进行了单晶结构解析,研究了其与ATP作用的液相NMR谱.该晶体属正交晶系,空间群为Pcan.晶胞参数a=0.7501(2)nm,b=2.3994(7)nm,c=1.2178(4)nm,Z=4.[Mo_0.4W_0.6O₂(C₆H₄O₂)₂]^2-的配位几何构型为手性八面体,晶体为外消旋体.配位阴离子中MoW中心金属离子除了与两个端基O配位形成cis-MO键外,同时还分别与两个邻苯二酚配位基团的的氧原子配位,形成4个M-Ob(M=Mo,W)键,构成两个五元环.利用¹HNMR,¹³CNMR,³¹PNMR以及¹H-¹⁵NHMBC对标题配合物及其与ATP在D₂O溶剂中的作用进行了研究,发现标题配合物的MoW中心金属离子在纯D₂O溶剂中被还原成+5价,但与ATP混合后转化为+6价,且与原配位基邻苯二酚发生解离.解离后的[MO₂]²⁺最大可能与腺嘌呤上的氨基N原子配位,而此配位可能是其抗癌抗肿瘤活性的主要作用机理之一.     

NMR Study of Pore Surface and Size in a Mesoporous Material FSM-16

Surface structure, pore size distribution and pore wall thickness of a mesoporous material FSM-16 have been studied by X-ray powder diffraction (XRD), ^lH and ²⁹Si MAS NMR and ¹H liquid-state NMR, and by applying surface silylation as a probe. Concentrations of surface hydroxyl groups for FSM-16 are estimated from ²⁹Si and ¹H MAS NMR, which are about 3×l0²¹ g^-1, corresponding to approximately 3 nm^-2. O₂ molecules contribute to ²⁹Si spin-lattice relaxation of Q² and Q³ as well as Q⁴, suggesting thin wall thickness. ¹H MAS NMR spectra indicate the presence of isolated and hydrogen-bonded hydroxyl groups. Both hydroxyl groups are silylated, where the silylated fraction is about 50%. The spatial distribution of surface hydroxyl groups is estimated from the line width in ¹H static spectra. A rather homogeneous distribution is demonstrated in one of the samples. The sample with less homogeneous distribution has a larger affinity for moisture. Pore size and pore wall thickness were determined by ¹H NMR measurements on water saturated FSM-16 samples, which are in good agreement with literature values obtained by N₂ adsorption isotherms and transmission electron micrographs on a similar sample. In benzene saturated samples, a non-freezing surface layer of benzene is much thicker than that of water, which indicates a stronger interaction between benzene and the FSM-16 surface.     

Synthesis and Biological Evaluation of Amino Alcohol Containing 1,3,4-Oxadiazole

A series of amino alcohol derivatives containing 1,3,4-oxadiazole moieties was synthesized with 7-bromo-2-tetralone as starting materials, 2,2-dimethyl-1,3-oxazolidine as intermediates and Strecker reaction and cyclization with POCl₃ as key steps. The structures of the key intermediate and target compounds were confirmed by ¹H NMR, ¹³C NMR and HRMS. Some compounds have resulted in the generation of highly potent sphingosine 1-phosphate receptor type 1(S1P₁) agonists.     

A H and C NMR study of the prototropic equilibria of 2-indolinone

¹³C NMR data are reported for 0.5 M solutions in CDCl₃ of 2-indolinone and six related compounds. The question of prototropic equilibria is discussed involving three possible tautomers, A, B, C. Form A is found to predominate in the dynamic equilibria established for three of the compounds studied. In the case of a fourth compound slow exchange between forms B and C results in the finding of both of these forms in the approximate ratio 1:1.8. These findings are supported by ¹H NMR measurements. Corresponding ¹H and ¹³H C NMR measurements on methanol solutions are essentially the same.     

酚类糖苷缀合物的合成、表征及美白活性

根据拼合原理,以对苯二酚(p-HQ)、间苯二酚(m-HQ)及邻苯二酚(o-HQ)为先导化合物,通过一侧酚羟基的苄基保护、引入溴乙酸甲酯、还原、与3种糖元偶联、脱除保护基得到9种目标化合物。 同样以3-(4-羟基苯基)-1-丙醇为起始物质,通过苄基保护、与3种糖元偶联、脱除保护基得到3种目标化合物。 通过IR、¹H NMR、¹³C NMR、HRMS等波谱分析方法对所合成的12种目标化合物进行了结构表征。 对合成的酚类糖苷缀合物进行了美白活性研究。 结果表明,化合物p-HQ-6a、m-HQ-7a、p-HQ-6b、m-HQ-6b、o-HQ-6b、p-HQ-6c、m-HQ-7c、L-3a和L-4b对酪氨酸酶有抑制作用,其中o-HQ-6b和p-HQ-6c对酪氨酸酶的抑制作用优于阳性对照物α-熊果苷。     

与二茂铁酰基相连的螺噁嗪的合成、结构及性质

在二环已基碳二亚胺(DCC)存在下, 将9′-羟基螺噁嗪与二茂铁甲酸进行酯化缩合, 合成了一种与二茂铁酰基相连的螺噁嗪衍生物2, 用核磁共振氢谱、碳谱、红外光谱、高分辨质谱和X射线单晶衍射对其结构进行了表征. 化合物2在几种有机溶剂中都表现出了良好的光致变色性质; 通过实验证明了在无冰水浴冷却条件下, 用高压汞灯照射时化合物2在二氯甲烷中表现出的特殊变色性是酸致变色的结果; 同时还研究了化合物2在固体PMMA薄膜中的光致变色性质. 在高压汞灯照射下,化合物2在二氯甲烷溶液中显示了良好的荧光性. 循环伏安法测定结果表明化合物2具有良好的氧化还原可逆性.     

P NMR investigation of a ringing gel phase and adjacent phases

The temperature-surfactant concentration phase diagram was examined for the dodecyltrimethylammonium dimethylphosphate/3-methyl-3-methoxybutanol/water ternary system. The phase diagram contained a highly elastic gel phase which is known as a “ringing gel phase”. The ringing gel phase and adjacent phases in the ternary system were investigated by polarized optical microscopy, freeze-fracture transmission electron microscopy, and ³¹P NMR. Globular textures were observed in an optically isotropic gel phase. Since the globules were larger than those found in an isotropic solution, the texture consists of domains of aggregated units in the cubic (I₁) phase. Structure units of domains are equivalent to microemulsions which are constructed by surfactant molecules and swollen by alcohol in the isotropic (L₁) phase. Characteristic polarized microscopic textures were visualized in two phases with higher surfactant concentrations. These phases were identified as being hexagonal (H₁) and lamellar (L) liquid crystals which was confirmed by transmission electron microscopy. The ³¹P NMR signal of the ringing gel showed a sharp singlet the same as that of the L₁ phase, indicating the fully averaged anisotropic interaction of the aggregates. The characteristic NMR signals of the anisotropic hexagonal and lamellar liquid crystal phases displayed chemical shielding with an asymmetric lineshape.     

Smenoqualone a novel sesquiterpenoid from the marine sponge Smenospongia sp.

Smenoqualone, a novel quinonic terpenoid with a rearranged drimane skeleton was isolated from a marine sponge Smenospongia sp. The stereostructure was determined by detailed analyses of ¹H and ¹³C NMR spectra, ¹H-¹H COSY, ¹H-¹³C correlations via HMQC, HMBC and NOE difference NMR experiments.     

Application of ionic liquids as a catalyst in the synthesis of polyvinyl butyral(PVB) polymer

Polyvinyl butyral(PVB) polymer was successfully synthesized using ionic liquid(IL) catalyst. The synthesis of PVB was achieved by acetalization of polyvinyl alcohol(PVA) and butyraldehyde(BA) in the presence of[HMIM]⁺HSO₄^- IL catalyst. The FT-IR, ¹H NMR, DSC, GPC and SEM characterizations were used to analyze the structure and properties of PVB. The effects of the concentration of PVA in water and the number of reuse cycles on the acetalization degree were investigated. The results indicated that the maximum acetalization degree of PVB obtained using[HMIM]⁺HSO₄^- IL catalyst was up to 72%. The comparison of the commercial PVB and the PVB obtained using[HMIM]⁺HSO₄^- IL catalyst showed that the self-made PVB has a larger molecular weight, higher viscosity, and higher acetalization degree than the commercial PVB.     

Catalytic promotion of piperonyl alcohol to trimethylendioxyorthocyclophane by bentonitic earth, or by hydrochloric acid

The cyclooligomerization of piperonyl alcohol (1) afforded trimethylendioxyorthocyclophane (2), a novel product, which was promoted by the catalytic action of a commercial bentonitic earth, Tonsil Actisil FF, as well as by hydrochloric acid in 1, 4-dioxane. The structure of 2 was established by ¹H, ¹³C NMR and HMQC experiments (DMSO-d₆ and in the solid state), and by the corresponding mass spectrometric data (EI, CID and HR).     

An NMR study of the conformational flexibility of phenyl acetate dissolved in a nematic liquid crystalline solvent

The ¹H, ²H and ¹³C NMR spectra of phenyl acetate, phenyl acetate-[¹³CO] and phenyl acetate-[C²H₃] dissolved in a nematic liquid crystalline solvent have been analysed to yield dipolar coupling, D_ij. These have been interpreted using the additive potential model to provide information on the molecular conformation, resulting in three possible shapes for V(φ), the potential energy for rotation about the ring-oxygen bond. A comparison with the results of molecular orbital calculations leads to the conclusion that a potential with a minimum at 54.4° ± 0.1° is the most probable.     

The structure of laurobtusol, a new rearranged sesquiterpenoid from the mediterranean red alga laurencia obtusa

An alcohol with a new tricyclic humulane skeleton, laurobtusol was isolated from the Mediterranean Red Alga Laurencia obtusa. The structure was established mainly by 2 D NMR methods and the relative configuration was assigned by a quantitative computer simulation of the lanthanide induced shifts in the ¹H NMR spectrum and Molecular Mechanics calculation (MM2).     

Microstructure determination of N-vinyl-2-pyrrolidone/butyl acrylate copolymers by NMR spectroscopy

The copolymer composition of N-vinyl-2-pyrrolidone/butyl acrylate (V/B) copolymers was determined from the quantitative ¹³C{¹H} NMR spectra. The monomer reactivity ratios for N-vinyl-2-pyrrolidone (V) and butyl acrylate (B) were found to be r_V=0.11±0.07, r_B=0.54±0.19, using the Kelen–Tudos and non-linear least-square error-in-variable (EVM) methods. The ¹³C{¹H} and ¹H NMR spectra of these copolymers are overlapping and complex. The complete spectral assignment of the carbon and proton NMR spectra were done by employing distortionless enhancement by polarization transfer (DEPT) and two-dimensional (2D) ¹³C–¹H heteronuclear single quantum correlation spectroscopy experiments. The 2D total correlation spectroscopy (TOCSY) (¹H–¹H homonuclear TOCSY) NMR spectrum was used to ascertain the various geminal and vicinal couplings in the copolymer.     

X-ray structure and multinuclear NMR studies of platinum(II) and palladium(II) complexes with 5,7-ditertbutyl-1,2,4-triazolo[1,5-a]pyrimidine

Pt(II) and Pd(II) dichloride complexes with 5,7-ditertbutyl-1,2,4-triazolo[1,5-a]pyrimidine (dbtp) have been synthesized and characterized by infrared and ¹H, ¹³C NMR, ¹³C CPMAS spectroscopy. The structures of the cis-PtCl₂(dbtp)₂ · EtOH (1) and cis-PdCl₂(dbtp)(dmso) (2) has been determined by signal-crystal X-ray diffraction. In both complexes the X-ray crystal structures shows that heterocycle ligand (dbtp) binds the central atom monodentate via nitrogen atom N(3). In addition, compound (2) is interesting for its structural features, because it is the first report of mixed dichloride Pd(II) complexes with N-donor (triazolopyrimidine) and S-donor (dimethylsulfoxide) ligands. In this structure the Pd–Cl distances are: 2.302(1) and 2.281(1) Å, Pd–N 2.041(3) Å and Pd–S 2.245(1) Å. The ¹H, ¹³C NMR studies show clearly that these structures are retained in solution.     

Dispersion of stratum corneum in an aqueous mixed solution of surfactants: the effect of a mixture of sodium dodecyl sulfate and N,N-dimethyldodecylamine oxide

Molecular interactions between sodium dodecyl sulfate (SDS) and N,N-dimethyldodecylamine oxide (C₁₂DMAO), whose mixtures were effective for dispersion of stratum corneum (SC) into intact corneocytes, were studied and found to be strongest at an SDS/C₁₂DMAO molar ratio of 1/3, when dispersion of SC was most effective and the sizes of the mixed micelles were largest.

This dispersion effect was confirmed as being caused by the stronger solubilizing power of molecular complexes formed between SDS and C₁₂DMAO in the binary mixed solutions by using ¹H NMR. The mechanisms for removing intercellular lipids such as ceramides, cholesterol and their derivatives, which play an important role as adhesives among the corneocytes, and for dispersing SC into intact cells were proposed on the basis of supporting data obtained from ¹H-NMR and light scattering measurements.     

键联环糊精、糖苷的卟啉及金属卟啉的合成

全甲基化-6-羟基-β-环糊精(PMβ-CD-CH₂OH)在N₂气流下与三氟甲基磺酸酐反应得到全甲基化-6-三氟甲基磺酸酯-β-环糊精(PMβ-CD-CH₂OTf)(6).6分别与5-(p-氨基苯基)-10,15,20-三苯基镍(钌羰基)卟啉[NiTP_NH2P](2)和[Ru(CO)TP_NH2P](3)缩合得到化合物7和8.1-溴-2,3,4,6-O-乙酰基-α-D-葡萄糖(4)和1-溴-2,3,5-O-乙酰-β-D-呋喃糖(5)分别与H₂TP_NH2P(1)反应得到化合物9和10.新化合物6-10经IR,UV-Vis,¹HNMR和元素分析确证,其中化合物6由MS谱进一步确定.