Precise Structural and Dynamical Details in Zeolites Revealed by Coupling-Edited H-O Double Resonance NMR Spectroscopy.

Despite the extensive industrial and research interests in zeolites, their intrinsic catalytic nature is not fully understood due to the complexity of the hydroxyl-aluminum moieties. O NMR would provide irreplaceable opportunities for much-needed fine structural determination given the ubiquitous presence of oxygen atoms in nearly all species; however, the low sensitivity and quadrupolar nature of oxygen-17 make its NMR spectroscopic elucidation challenging. Here, we show that state-of-the-art double resonance solid-state NMR techniques have been combined with spectral editing methods based on scalar (through-bond) and dipolar (through-space) couplings, which allowed us to address the subtle protonic structures in zeolites.

Direct Detection of Reactive Gallium-Hydride Species on the GaO Surface Solid-State NMR Spectroscopy.

Surface metal hydrides (M-H) are ubiquitous in heterogeneous catalytic reactions, while the detailed characterizations are frequently hindered by their high reactivity/low concentration, and the complicated surface structures of the host solids, especially in terms of practical solid catalysts. Herein, combining instant quenching capture and advanced solid-state NMR methodology, we report the first direct and unambiguous NMR evidence on the highly reactive surface gallium hydrides (Ga-H) over a practical GaO catalyst during direct H activation. The spectroscopic effects of Ga and Ga isotopes on the H NMR signal are clearly differentiated and clarified, allowing a concrete discrimination of the Ga-H signal from the hydroxyl crowd.

Emerging roles of protein phosphorylation in plant iron homeostasis.

Remarkable progress has been made in dissecting the molecular mechanisms involved in iron (Fe) homeostasis in plants, especially the identification of key transporter and transcriptional regulatory networks. But how the protein activity of these master players is regulated by Fe status remains underexplored. Recent studies show that major players toggle switch their properties by protein phosphorylation under different Fe conditions and consequently control the signaling cascade and metabolic adjustment.

Unraveling the Surface Hydroxyl Network on InO Nanoparticles with High-Field Ultrafast Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy.

Hydroxyl groups are among the major active surface sites over metal oxides. However, their spectroscopic characterizations have been challenging due to limited resolutions, especially on hydroxyl-rich surfaces where strong hydroxyl networks are present. Here, using nanostructured InO as an example, we show significantly enhanced discrimination of the surface hydroxyl groups, owing to the high-resolution H NMR spectra performed at a high magnetic field (18.

Acidity and Local Confinement Effect in Mordenite Probed by Solid-State NMR Spectroscopy.

Herein, utilizing acetonitrile as the probe molecule, the acidity and host-guest interactions of H-mordenite (H-MOR) zeolites are investigated comprehensively by solid-state NMR spectroscopy and theoretical calculation. The locations and local configurations of Brønsted acid sites (BASs) in H-MOR are revealed by multinuclear and multidimensional NMR experiments with adsorption/coadsorption of acetonitrile (CDCN) and trimethylphosphine (TMP). Moreover, the confinement effect of dual pores in MOR has been characterized via the quantitative determination of host-guest interactions between CHCN and BASs.

Identification of different carbenium ion intermediates in zeolites with identical chabazite topology C-C through-bond NMR correlations.

C-C through-bond NMR correlation experiments reveal the stabilization of different carbenium ion intermediates in two zeolites possessing identical CHA topology (H-SAPO-34 and H-SSZ-13) during the methanol to olefins reaction.

Mapping the dynamics of methanol and xenon co-adsorption in SWNTs by in situ continuous-flow hyperpolarized Xe NMR.

A comparative study of the adsorption and desorption processes of methanol in two kinds of nanochannels (i.e. MCM-41 and SWNTs) is performed by in situ continuous-flow laser-hyperpolarized 129Xe NMR.

Fast detection and structural identification of carbocations on zeolites by dynamic nuclear polarization enhanced solid-state NMR.

Acidic zeolites are porous aluminosilicates used in a wide range of industrial processes such as adsorption and catalysis. The formation of carbocation intermediates plays a key role in reactivity, selectivity and deactivation in heterogeneous catalytic processes. However, the observation and determination of carbocations remain a significant challenge in heterogeneous catalysis due to the lack of selective techniques of sufficient sensitivity to detect their low concentrations.

Direct structural identification of carbenium ions and investigation of host-guest interaction in the methanol to olefins reaction obtained by multinuclear NMR correlations.

Probing and determining the intermediates formed during catalytic reactions in heterogeneous catalysis are strong challenges. Using C labelling and two dimensional C-C through-bond NMR correlations, we directly reveal the structures of a range of carbenium ion species formed during the conversion of methanol to olefins on acidic H-ZSM-5 zeolite by mapping the carbon-carbon bond connectivities. Additionally, we use C-Al and Si-C through-space NMR experiments to probe the interactions between the confined carbon species (including carbenium ions) and the framework of the zeolite, which quantitatively provide an estimate for the carbon-aluminium and carbon-silicon distances, respectively.

Direct observation of DME carbonylation in the different channels of H-MOR zeolite by continuous-flow solid-state NMR spectroscopy.

The dynamic evolution of acetyl intermediates in the two different channels of H-mordenite (H-MOR) zeolite during dimethyl ether (DME) carbonylation is tracked by using in situ solid-state NMR spectroscopy under continuous-flow conditions. Thus, the reaction path via methyl acetate produced over active sites in 8 member ring (MR) channels, followed by diffusion into 12 MR channels, is proposed.

Diffusion of water inside carbon nanotubes studied by pulsed field gradient NMR spectroscopy.

Diffusion dynamics of guest molecules in nanopores has been studied intensively because diffusion is center on a number of research fields such as separation, drug delivery, chemical reactions, and sensing. In the present work, we report an experimental investigation of the self-diffusion of water inside carbon nanotube (CNT) channels using a pulsed field gradient (PFG) NMR method. The dispersion of CNTs homogeneously in water and cooling to temperatures below the melting point of bulk water allow us to probe the translational motion of confined water molecules.

Synthesis and characterization of a compact tricyclic resorcinol from (+)- and (-)-3-pinanol.

Resorcinol derivatives are important building blocks in the synthesis of natural products and pharmaceutical compounds including cannabinoids. Here we describe the synthesis and the structural characterization of a key resorcinol which carries a fully restricted bridged bicyclic group. We also report a potential mechanism for the acid catalyzed condensation of (+)- or (-)-3-pinanol with 2,6-dimethoxyphenol.

Ionothermal synthesis process for aluminophosphate molecular sieves in the mixed water/ionic liquid system.

The synthesis process of aluminophosphate AlPO(4)-11 molecular sieve in the mixed water/1-butyl- 3-methylimidazolium bromide ([bmim]Br) ionic liquid was investigated by XRD, multinuclear solid-state NMR, scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS). It was observed that a tablet phase, named SIZ-2, was formed at the early stage of crystallization. During crystallization metastable SIZ-2 with an incompletely condensed framework phosphorus disappeared gradually, and the phosphorous species became fully condensed through hydroxyl reaction with tetrahedral aluminum to form thermodynamically stable AlPO(4)-11 in the final product.

In situ solid-state NMR for heterogeneous catalysis: a joint experimental and theoretical approach.

In situ solid-state NMR is a well-established tool for investigations of the structures of the adsorbed reactants, intermediates and products on the surface of solid catalysts. The techniques allow identifications of both the active sites such as acidic sites and reaction processes after introduction of adsorbates and reactants inside an NMR rotor under magic angle spinning (MAS). The in situ solid-state NMR studies of the reactions can be achieved in two ways, i.

Density functional calculations on the distribution, acidity, and catalysis of Ti(IV) and Ti(III) ions in MCM-22 zeolite.

Isolated Ti species in zeolites show unique catalytic activities for a variety of chemical reactions. In this work, density functional calculations were used to explore three current concerns: 1) the distributions of Ti(IV) and Ti(III) ions in the MCM-22 zeolite; 2) the Lewis acidity of the Ti(IV) and Ti(III) sites; and 3) activation of alkane C-H bonds by photocatalysis with Ti-doped zeolites. Neither the Ti(IV) nor Ti(III) ions are randomly distributed in the MCM-22 zeolite.

Novel 1',1'-chain substituted hexahydrocannabinols: 9β-hydroxy-3-(1-hexyl-cyclobut-1-yl)-hexahydrocannabinol (AM2389) a highly potent cannabinoid receptor 1 (CB1) agonist.

In pursuit of a more detailed understanding of the structural requirements for the key side chain cannabinoid pharmacophore, we have extended our SAR to cover a variety of conformationally modified side chains within the 9-keto and 9-hydroxyl tricyclic structures. Of the compounds described here, those with a seven-atom long side chain substituted with a cyclopentyl ring at C1' position have very high affinities for both CB1 and CB2 (0.97 nM < K(i) < 5.

Cooperative structure-directing effect in the synthesis of aluminophosphate molecular sieves in ionic liquids.

In situ two-dimensional NMR and fluorescence emission spectroscopy were employed to investigate the cooperative structure-direction effect of organic amine such as morpholine in the synthesis of aluminophosphate molecular sieves in ionic liquids. In situ rotating frame nuclear Overhauser effect spectra (ROESY) together with fluorescence measurements demonstrate that the aggregates between imidazolium cations and morpholines through intermolecular hydrogen bonds can be formed in the gel during the crystallization of molecular sieves. Combining with the characterizations of the solid products by solid-state NMR, it is verified that different aggregates of organic amines with imidazolium cations, which is similar to self-assembled supramolecular analogues, could act as the structure-directing agents for selective tuning of the framework topologies such as AEL, AFI and LTA in the final solid products.

[A rudimentary study of the acid fibroblast growth factor's plant expression vector construction and transformation tobacco].

Acid fibroblast growth factor (aFGF) has great potential in clinical application, but it is very expensive. In order to reduce the cost of production and to make full use of the merits integrated with plant bioreator, we have explored the aFGF in transgenic Tobacco expression. AFGF gene was inserted into plant expression vector pBI121; the acquired plants contained aFGF gene expression vector pBI121-TOAB-aF.

[Establishment of transgenic receptor system and aFGF transformation in astragalus].

Objective: To establish a high-frequency regeneration system of Astragalus and an aFGF transformation system.

Method: Cotyledon node of the Astragalus explants was used for organogenesis to establish a high-frequency regeneration system. GV3101 was used to transform cotyledon node, and aFGF gene was introduced into Astragalus, renewable strain was detected by PCR.

Template-synthesized porous silicon carbide as an effective host for zeolite catalysts.

A facile method has been developed for the fabrication of porous silicon carbide (SiC) by means of sintering a mixture of SiC powder and carbon pellets at a relatively lower temperature, that is, 1450 degrees C, in air. The pore density and the total pore volume of the resulting porous SiC could be tuned by changing the initial SiC/C weight ratio. The structure evolution and the associated property changes during the preparation were examined through X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, (29)Si magic-angle spinning (MAS) NMR spectroscopy, and mercury-intrusion porosimetry analyses.

Enhanced in situ continuous-flow MAS NMR for reaction kinetics in the nanocages.

A new approach of in situ continuous-flow laser-hyperpolarized (129)Xe MAS NMR together with (13)C MAS NMR is designed and applied successfully to study the adsorption and reaction kinetics in the nanospace. Methanol conversion in CHA nanocages has been investigated in detail for proof of principle demonstrating the prospect of in situ NMR of reaction kinetics. Our findings well elucidates that the reaction intermediate can be identified by (13)C MAS NMR spectroscopy, meanwhile the kinetic and dynamic processes of methanol adsorption and reaction in CHA nanocages can be monitored by one- and two-dimensional hyperpolarized (129)Xe MAS NMR spectroscopy under the continuous-flow condition close to the real heterogeneous catalysis.

New insights into the role of amines in the synthesis of molecular sieves in ionic liquids.

A combination of state-of-the art in situ one- and two-dimensional NMR spectroscopy and density functional theory (DFT) calculations have been employed for the first time to investigate the role of amines in the synthesis of aluminophosphate molecular sieves in ionic liquids (ILs). In situ rotating-frame nuclear Overhauser effect spectroscopy (ROESY) was used to demonstrate that the hybrid of imidazolium ionic liquids with organic amines, such as morpholine, connected through a hydrogen bond can be formed in the gel during the crystallization of molecular sieves. By combining the characterizations of the final solid products obtained by using XRD analyses, solid-state NMR spectroscopy, thermogravimetric analysis, and DFT calculation results, it was verified that the hybrid between morpholine and the imidazolium cation in the initial preparation stage can act as the structure-directing agent (SDA) for the synthesis of AFI-structured aluminophosphate molecular sieves.

Tandem ring-opening/closing reactions of N-Ts aziridines and aryl propargyl alcohols promoted by t-BuOK.

t-BuOK was found to be an effective promoting reagent for tandem ring-opening/closing reactions of various N-Ts aziridines and aryl propargyl alcohols to afford dihydroxazine derivatives in moderate to good yields. A plausible reaction mechanism has been proposed.

Probing the porosity of cocrystallized MCM-49/ZSM-35 zeolites by hyperpolarized 129Xe NMR.

One- and two-dimensional 129Xe NMR spectroscopy has been employed to study the porosity of cocrystallized MCM-49/ZSM-35 zeolites under the continuous flow of hyperpolarized xenon gas. It is found by variable-temperature experiments that Xe atoms can be adsorbed in different domains of MCM-49/ZSM-35 cocrystallized zeolites and the mechanically mixed counterparts. The exchange of Xe atoms in different types of pores is very fast at ambient temperatures.