Studies on the Synthesis and the Structure of Ferric Aluminum Magnesium Hydrotalcite—like Compounds

Hydrotalcite-like compounds (HTlc) are composed of trivalent and divalent metal ions, the general formula 1 is: [M2+1-xM3+x(OH)2]x+An-x/n·mH2O M3+ is trivalent metal ions, M2+is divalent metal ions, A is negative ions whose valence is n, and m is the amount of water in the crystal, and x is the molar ratio of trivalent metal ions to all metal ions. A lot of studies have been done on the synthesis and property of HTlc, which is made up of two kinds of the metal ions. It has been found …     

THE EXTRACTION OF GOLD FROM CYANIDE SOLUTION BY α—ALKYL SUBSTITUTED PYRIDINE RESIN

In this paper,we have studied the adsorption properties of gold by α-alkyl substituted pyridine resin( BPR) in alkaline solution.The single and dual component kinetic mass transfer process of Au(I),Ag(I) and other metal cyanide ions were also investigated.The results obtained show that the mass transfer rates of the cyanide ions in the resin phase are closely related to the molar ratio and the configuration of metal cyanide ions. The elution kinetics of Au(I) and other cyanide ions by NH4SCN has been investigated systematically.The intraparticle diffusion coefficient and activation energy of Au(I),Ag(I),Ni(I) Fe(Ⅲ） cyanide anions were determined in CI,NO3,OH-type BPR resin at different temperatures.It is found from the experimental results that the mechanism for extracting Au(I),Ag(I) and other metal cyanide anions by BPR resin belongs to ion exchange process.The difference of activation entropy of some metal cyanide anions(ΔS-ΔS^-) was evaluated.     

Synthesis and Study on the Complexation of Dithidiaza 21-Cown-7- Bearing Appended Coumarin or 1-Aminonaphthene as Sidearms

The high toxicity of many transition and post-transition metal ions, especially Hg2+ and Pb2 + , is well recognized and a lot of attention has been paid to control contamination of water supplies by toxic metal ions and to monitor the level of these metal ions in the environment. For the application purpose in controlling and monitoring the concentrations of specific metal ions in a complex matrix continuously and remotely by using ion-selective sensory devices, chemical sensors based on the synthetic fluoroionophores and chromoionophores capable of signaling complexation of metal ions have been reported, [1～ 5], and a series of dithidiaza 21-rown-7 bearing appended coumarin or 1-aminonaphthene as sidearms was synthesized. [6]     

Synthesis and Crystal Structure of a Hydrogen-bonded Supramolecular Compound [(C_6H_5N_2O)_3·Cu_1._5]·6H_2O

1 INTRODUCTION The binding of metal ions by proteins and pep- tides is of fundamental interest due to the impor- tance of metal ions in biological systems. Metals may be part of the active sites of enzymes, stabilize the macromolecular structure of proteins and affect enzymes or membranes to control cell metabolism[1]. Therefore, for many years there has been a great in- terest in the study of complexes able to mimic these active sites of metalloproteins. In this case, metal complexes of…     

Catalytic Kinetics of the Schiff Base Metal Complexes Bearing Side Chain of Cyclic morpholine in Carboxylic Ester Hydrolysis

It has been reported that two Schiff base transition metal complexes bearing the side chain of the morpholine ring were synthesized and characterized, and two complexes with the same base agent but different metal ions were used as a simulant hydrolase in the catalytic hydrolysis of p-nitrophenyl picolinate in this paper. The mechanism of PNPP catalytic hydrolysis is proposed and supported by the results of the spectral analysis and the kinetic calculation. A kinetic mathematical model, applied to the calculation of the kinetic and thermodynamics parameters of PNPP catalytic hydrolysis, has been established on the foundation of the mechanism proposed. The result of the study shows that the two complexes have a good catalytic activity in PNPP catalytic hydrolysis, and the rate of the PNPP catalytic hydrolysis was increased with the increase of the pH values in the buffer solution and affected by the polarization effect of metal ion of the complexes.     

One-dimensional Copper(II) Complex Constructed with Nitrate Counter-anion as Bitopic Connector

The design and synthesis of supramolecular structures has become an area of intense research in recent two decades.By carefully choosing the ions and ligands,frameworks with interesting and desirable properties can be created1-2.Essence of supramolecular chemistry is the self-assembly process of diversified interactions,such as metal-ligand coordination,hydrogen bonding,π-πstacking,etc.In contrast to the well-studied metal ions and ligands,there are relatively few examples about anionic func…     

A Novel Platinum（Ⅳ） Halide Anion as Ethyl-triphenylphosphenonium Salt： Synthetic, Structural and Theoretical Study

1 INTRODUCTION The importance of metal ions in nucleic acid and other biologic processes has stimulated considerable research interest in the area of metal interactions with nuclei acid constituents[1, 2] due to the discovery that some platinum compounds, especially cis-Pt (NH3)2- Cl2, exhibit carcinostatic properties[3]. This has led to an increased research activity in the chemistry and structures of platinum complexes containing novel or- ganic ligands. And crystal engineering has its…     

A Three-dimensional Heteronuclear Polymer of [Ag2Fe（SCN）5（DMF）]n Containing Channels and One-dimensional Ag2S2-S-Ag2S2 Chains with Ag…Ag Interaction

Introduction So far, considerable attention has been paid to mag-netic interaction between two different metal ions.1-3 As a potential bridging ligand, thiocyanate can coordinate to a harder metal center with N atom and softer ones with S atom at the same time, resulting in the formation of small ferromagnetic coupling.2 On the other hand, the Fe(III) atom is a good candidate as a hard acid and Ag(I) is a good candidate as a soft acid, so that the Fe(III) centers could be expected to conn…     

FT-Raman Spectroscopic Studies on the Interaction of Metal Ions With Sphingomyelin Bilayer

The interaction of trivalent lanthanide ions and divalent calcium ions with sph-'ngomyelm bilayer has been studied by FT-Raman spectroscopy.The results showed that the bonding of metal ions to the phosphate group of sphingomyelin bi-iayer,either La3 or Ca2 did not change the conformation of the choline group,that is,O-C-C-N is still in its gauche conformation.The presence of metal ions changed the states of the interfacial region from liquid-like to amorphous state and even to crystalline.They increased the fluidity of acyl chains of sphingomyelin bilaver and made them packed disorderly.     

Synthesis and Structure of Bis（indene—1,2,3—trione 2—oximato）bis （aqua）Mn（Ⅱ）：Mn（C9H4NO3）2（H2O）2

1 INTRODUCTION The interest in the complexes of transition metals with ligands ketoxime[1, 2] as potential models for metal binding sites in ferroverdin[3, 4] has prompted the investigation on the structures and the overall coordination geometry of the metal centers in these complexes. Oxime derivatives are interesting ligands since the ketoximes are found to chelate transition metals through the N (oxime) and O (ketone) atoms[5, 6]. However, monodentate coordination via only one O or …     

移动床热煤气脱硫气固反应过程模拟Ⅲ错流及逆、并流移动床反应器的比较

基于前文对错流移动床反应器的分析,进一步建立了逆、并流移动床非催化气固反应器模型方程,对不同操作条件下错流和逆、并流三类移动床反应器的行为进行了比较。结果表明,三类不同气固接触方式移动床的行为存在差异,其根本原因在于其内进行的非催化气固反应过程受固剂转化率的影响,当反应属本征动力学或内扩散控制时,错流、逆流移动床的床层利用效率较高,但反应属外扩散控制如在加压条件下操作或所要求的固剂转化率可降低时,三类移动床反应器床层利用效率趋于一致。     

Rapid 1H[13C]-resolved diffusion and spin-relaxation measurements by NMR spectroscopy

Hadamard-encoded heteronuclear-resolved NMR diffusion and relaxation measurements allow overlapping signal decays to be resolved with substantially shorter measuring times than are generally associated with 2D heteronuclear cross-correlation experiments. Overall measuring time requirements can be reduced by approximately an order of magnitude, compared to typical 2D heteronuclear single-quantum correlation-resolved diffusion or relaxation measurements. Specifically, in cases where chemical shift correlation information provides enhanced spectral resolution, the use of Hadamard encoding can be used to overcome uniqueness challenges that are associated with the analysis of concurrent dynamic processes and the extraction of time constants from overlapping exponential signal decays. This leads to substantially improved resolution of similar time constants than can be achieved solely through the use of post-acquisition processing techniques. In the ideal case of complete spectral separation of the signal decays, the usual constraint that time constants must be sufficiently different to resolve by exponential analysis can be circumvented entirely. Hadamard-based pulse sequences have been used to determine 1H[13C]-resolved diffusion coefficients and spin-relaxation time constants for the chemically similar components of an aqueous solution of ethanol, glycerol, and poly(ethylene glycol), and a dye-containing block-copolymer solution, which exhibit significant spectral overlap in their 1H NMR spectra.     

Self-Assembly Behavior of Benzotriazole in Water

The self-assembly behavior of ¹H-benzotriazole (BTA) in aqueous solutions below its solubility limit has been revealed for the first time using NMR and light scattering techniques. Relaxation time, diffusion and chemical shift NMR techniques in addition to various light scattering techniques were used to study the aqueous behavior of ¹H-Benzotriazole (BTA). These studies have revealed the self assembly of BTA molecules in water. Results show that BTA molecules tend to aggregate in water to form nanoparticles with radius in the range of 5 nm. The critical aggregation concentration (CAC) is estimated based on NMR data to be ～16–20 mM. Such a critical aggregation concentration is comparable with the typical critical micelle concentration (CMC) for surfactants that have moderate aqueous solubility. The self-assembly behavior of BTA may not be limited to benzotriazole. It might be generally true for all poorly water soluble species to aggregate at concentrations below their solubility.     

1H‐19F REDOR‐filtered NMR spin diffusion measurements of domain size in heterogeneous polymers

Solid state NMR spectroscopy is inherently sensitive to chemical structure and composition and thus makes an ideal method to probe the heterogeneity of multicomponent polymers. Specifically, NMR spin diffusion experiments can be used to extract reliable information about spatial domain sizes on multiple length scales, provided that magnetization selection of one domain can be achieved. In this paper, we demonstrate the preferential filtering of protons in fluorinated domains during NMR spin diffusion experiments using ¹H‐¹⁹F heteronuclear dipolar dephasing based on rotational echo double resonance (REDOR) MAS NMR techniques. Three pulse sequence variations are demonstrated based on the different nuclei detected: direct ¹H detection, plus both ¹H?¹³C cross polarization and ¹H?¹⁹F cross polarization detection schemes. This ¹H‐¹⁹F REDOR‐filtered spin diffusion method was used to measure fluorinated domain sizes for a complex polymer blend. The efficacy of the REDOR‐based spin filter does not rely on spin relaxation behavior or chemical shift differences and thus is applicable for performing NMR spin diffusion experiments in samples where traditional magnetization filters may prove unsuccessful. This REDOR‐filtered NMR spin diffusion method can also be extended to other samples where a heteronuclear spin pair exists that is unique to the domain of interest.     

Polymorphism of N,N'-diacetylbiuret studied by solid-state 13C and 15N NMR spectroscopy, DFT calculations, and X-ray diffraction

The molecular configuration and crystal structure of solid polycrystalline N,N′′‐diacetylbiuret (DAB), a potential nitrogen‐rich fertilizer, have been analyzed by a combination of solid‐ and liquid‐state NMR spectroscopy, X‐ray diffraction, and DFT calculations. Initially a pure NMR study (“NMR crystallography”) was performed as available single crystals of DAB were not suitable for X‐ray diffraction. Solid‐state ¹³C NMR spectra revealed the unexpected existence of two polymorphic modifications (α‐ and β‐DAB) obtained from different chemical procedures. Several NMR techniques were applied for a thorough characterization of the molecular system, revealing chemical shift anisotropy (CSA) tensors of selected nuclei in the solid state, chemical shifts in the liquid state, and molecular dynamics in the solid state. Dynamic NMR spectroscopy of DAB in solution revealed exchange between two different configurations, which raised the question, is there a correlation between the two different configurations found in solution and the two polymorphic modifications found in the solid state? By using this knowledge, a new crystallization protocol was devised which led to the growth of single crystals suitable for X‐ray diffraction. The X‐ray data showed that the same symmetric configuration is present in both polymorphic modifications, but the packing patterns in the crystals are different. In both cases hydrogen bonds lead to the formation of planes of DAB molecules. Additional symmetry elements, a two‐fold screw in the case of α‐DAB and a c‐glide plane in the case of β‐DAB, lead to a more symmetric (α‐DAB) or asymmetric (β‐DAB) intermolecular hydrogen‐bonding pattern for each molecule.     

The structure elucidation of isomalyngamide K from the marine cyanobacterium Lyngbya majuscula by experimental and DFT computational methods

The 2Z-isomer of malyngamide K has been isolated along with the known compounds malyngamide C, deoxy-C and K, and characterized from a Papua New Guinea field collection of the cyanobacterium Lyngbya majuscula. The planar structure was deduced by 1D and 2D NMR spectroscopic and mass spectral data interpretation. The absolute configurations were determined on the basis of spectroscopic techniques, chemical degradation and DFT theoretical calculations.     

First-principles calculation of 17O and 25Mg NMR shieldings in MgO at finite temperature: rovibrational effect in solids

The temperature dependence of (17)O and (25)Mg NMR chemical shifts in solid MgO have been calculated using a first-principles approach. Density functional theory, pseudopotentials, a plane-wave basis set, and periodic boundary conditions were used both to describe the motion of the nuclei and to compute the NMR chemical shifts. The chemical shifts were obtained using the gauge-including projector augmented wave method. In a crystalline solid, the temperature dependence is due to both (i) the variation of the averaged equilibrium structure and (ii) the fluctuation of the atoms around this structure. In MgO, the equilibrium structure at each temperature is uniquely defined by the cubic lattice parameters, which we take from experiment. We evaluate the effect of the fluctuations within a quasiharmonic approximation. In particular, the dynamical matrix, defining the harmonic Hamiltonian, has been computed for each equilibrium volume. This harmonic Hamiltonian was used to generate nuclear configurations that obey quantum statistical mechanics. The chemical shifts were averaged over these nuclear configurations. The results reproduce the previously published experimental NMR data measured on MgO between room temperature and 1000 degrees C. It is shown that the chemical shift behavior with temperature cannot be explained by thermal expansion alone. Vibrational corrections due to the fluctuations of atoms around their equilibrium position are crucial to reproduce the experimental results.     

NMR of Natural Products as Potential Drugs

This review outlines methods to investigate the structure of natural products with emphasis on intramolecular hydrogen bonding, tautomerism and ionic structures using NMR techniques. The focus is on 1H chemical shifts, isotope effects on chemical shifts and diffusion ordered spectroscopy. In addition, density functional theory calculations are performed to support NMR results. The review demonstrates how hydrogen bonding may lead to specific structures and how chemical equilibria, as well as tautomeric equilibria and ionic structures, can be detected. All these features are important for biological activity and a prerequisite for correct docking experiments and future use as drugs.     

Nuclear magnetic resonance studies of solvent flow through chromatographic columns: effect of packing density on flow patterns

NMR (nuclear magnetic resonance) techniques have been used to measure and characterise solvent flow through chromatographic columns. NMR imaging was used to track an injection of D2O. PGSE (pulsed gradient spin echo) NMR was used to measure the flow-rate dependence of axial and transverse apparent diffusion. A combination of these two techniques (dynamic NMR imaging) gave the spatial distribution of the local velocity and apparent diffusion through a cross-section of the column. Significant column wall effects were observed and these effects were found to be highly dependent upon the column packing density. The column performance was assessed in terms of the HETP (height equivalent to a theoretical plate) determined by the NMR techniques employed.     

Hopping dynamics and diffusion of atoms,molecules, and ions in nanoporous solids by exchange NMR spectroscopy

Molecular diffusion in nanoporous materials can be understood as series of dynamic hopping or exchange motions of molecules between different discrete sites. Exchange NMR offers the spectral resolution to distinguish between these different sites, based on isotropic and anisotropic NMR interactions that manifest differences in the local chemical or structural environments of molecules at different sites or their local orientations. Such interactions facilitate the observation of distinct adsorption environments and provide insights on the number and distributions of distinct types of environments and the geometries and motional correlation times of local hopping events between different sites. The temporal range accessible by exchange NMR is governed by the time required for the observation of the NMR signal (<?1 ms) and the return of the nuclear magnetic polarization to thermal equilibrium (typically several seconds). Over such timescales, this permits slow molecular exchange processes between local environments to be probed in great quantitative detail. The resulting insights on dynamic exchange or hopping of atoms, molecules, or ions in nanoporous solids provide a basis for understanding processes that occur over longer length and time scale, which ultimately account for their macroscopic diffusion properties.