Boson peak of alkali and alkaline earth silicate glasses: influence of the nature and size of the network-modifying cation

The influence of the size of the alkaline earth cation on the boson peak of binary metasilicate glasses, MSiO(3) (M = Mg, Ca, Sr, Ba), has been investigated from vibrational densities of states determined by inversion of low-temperature heat capacities. As given both by C(p)/T(3) and g(ω)/ω(2), the intensity of the boson peak undergoes a 7-fold increase from Mg to Ba, whereas its temperature and frequency correlatively decrease from 18 to 10 K and from 100 to 20 cm(-1), respectively. The boson peak results from a combination of librations of SiO(4) tetrahedra and localized vibrations of network-modifying cations with non-bridging oxygens whose contribution increases markedly with the ionic radius of the alkaline earth. As a function of ionic radii, the intensity for Sr and Ba varies in the same way as previously found for alkali metasilicate glasses. The localized vibrations involving alkali and heavy alkaline earth cations appear to be insensitive to the overall glass structure. Although the new data are coherent with an almost linear relationship between the temperature of the boson peak and transverse sound velocity, pure SiO(2) and SiO(2)-rich glasses make marked exceptions to this trend because of the weak transverse character of SiO(4) librations. Finally, the universality of the calorimetric boson peak is again borne out because all data for silicate glasses collapse on the same master curve when plotted in a reduced form (C(P)∕/T(3))/(C(P)/T(3))(b) vs. T/T(b).     

Kinetics of ion-exchange of alkaline earth metals on antimony(V) phosphate cation exchanger

Forward and reverse ion exchange kinetics of Mg(II), Ca(II), Sr(II) and Ba(II) exchange with H(I) has been studied on antimony(V) phosphate cation exchanger applying the Nernst-Planck equations. As a result, some kinetic parameters like diffusion coefficients, activation energies, and entropies of activation have been evaluated under the conditions favoring a particle diffusion-controlled mechanism. Such kinetic parameters have also been compared with the kinetic parameters of different single and double salts.     

Three iodometalate organic-inorganic hybrid materials based on methylene blue cation: Syntheses,structures, properties and DFT calculations

The functional dye of methylene blue (MB) has been employed for seeking new organic–inorganic hybrid photochromic materials. Although the photochromism has not been observed yet, three iodometalate compounds, namely (MB) (PbI₃) (DMF) (1), (MB)₄(Cu₂I₄)₂ (2), and (MB)₃(Bi₂I₉) (DMF)₂ (3), have been synthesized and characterized. The iodometalate anion features as a [PbI₃]_∞⁻ chain in 1, a dinuclear unit of Cu₂I₄^2- in 2, and a dinuclear unit of Bi₂I₉³⁻ in 3. Due to the synergy of cations and anions, the MB⁺ cations present supramolecular column stacks in 1 and 3, but a novel supramolecular octamer structure in 2. Their thermogravimetric analyses reveal that the polymeric inorganic anion structure is helpful to increase the stability of cation whereas the discrete structure is adverse. For seeking some clues which is significant to searching new photochromic systems, the density functional theory (DFT) studies have been performed on 1, in which the electronic structure analyses suggests that the stacking mode of cations and anions could be also an important factor influencing the charge transfer between them. In addition, dielectric hysteresis loop testing has been performed on 1 due to its polar space group of Cc.     

Three alkaline earth metal-organic frameworks based on fluorene-containing carboxylates: syntheses,structures and properties

Three metal-organic frameworks,{[Mg_2(MFDA)_2(DMF)_3]·0.5H_2O}_n(1),{[Ca(MFDA)(DMF)(H_2O)]·0.5DMF}_n(2)and[Ca(MFDA)(DMF)_2]_n(3)(DMF=N,N-dimethylformamide)have been synthesized by the solvothermal reactions between the ligand 9,9-dimethylfluorene-2,7-dicarboxylic acid(H_2MFDA)and the corresponding metal salts,respectively.The single crystal X-ray structural analyses reveal that compounds 1-3 display three-dimensional structures based on the M(Ⅱ)-O-C chains.It is interesting that the MFDA ligands in 1-3 have different dihedral angles between the two carboxylate groups ranging from 9.9(1)°to 41.8(2)°.All of compounds exhibit strong ligand-centered blue emissions under UV lights.Their thermal properties have also been studied.     

Synthesis and characterization of crystalline structures based on phenylboronate ligands bound to alkaline earth cations

We describe the preparation of the first crystalline compounds based on arylboronate ligands PhB(OH)(3)(-) coordinated to metal cations: [Ca(PhB(OH)(3))(2)], [Sr(PhB(OH)(3))(2)]·H(2)O, and [Ba(PhB(OH)(3))(2)]. The calcium and strontium structures were solved using powder and single-crystal X-ray diffraction, respectively. In both cases, the structures are composed of chains of cations connected through phenylboronate ligands, which interact one with each other to form a 2D lamellar structure. The temperature and pH conditions necessary for the formation of phase-pure compounds were investigated: changes in temperature were found to mainly affect the morphology of the crystallites, whereas strong variations in pH were found to affect the formation of pure phases. All three compounds were characterized using a wide range of analytical techniques (TGA, IR, Raman, XRD, and high resolution (1)H, (11)B, and (13)C solid-state NMR), and the different coordination modes of phenylboronate ligands were analyzed. Two different kinds of hydroxyl groups were identified in the structures: those involved in hydrogen bonds, and those that are effectively "free" and not involved in hydrogen bonds of any significant strength. To position precisely the OH protons within the structures, an NMR-crystallography approach was used: the comparison of experimental and calculated NMR parameters (determined using the Gauge Including Projector Augmented Wave method, GIPAW) allowed the most accurate positions to be identified. In the case of the calcium compound, it was found that it is the (43)Ca NMR data that are critical to help identify the best model of the structure.     

碱金属与碱土金属在煤炭热转化过程中的影响研究进展

对比阐述了AAEMs在煤炭热转化过程的影响与作用,论述了催化气化中炭结构转变、碱金属形态变化、催化剂失活等过程。AAEMs是催化气化的催化剂,是活性炭制备过程的造孔剂,也是高AAEMs煤利用过程的有害组分,同样也是煤灰提铝过程的焙烧活化剂。AAEMs与炭相互作用影响炭的表面结构,进而影响气化剂在炭表面的吸附与反应,而AAEMs与炭的相互作用也会影响AAEMs的挥发与释放,耦合催化气化与煤灰资源化利用可以有效降低催化剂回收成本。通过对比认识AAEMs在煤炭热转化中的影响与作用,以期为AAEMs作用下煤炭热转化过程提供新思路与方法。     

The photochemistry of a bis-crown ether based on benzobis(thiazole) and its alkaline earth metal cation complexes

Irradiation of acetonitrile solutions of the bis-crown ether E,E-2,7-bis[2-(6,7,9,10,12,13,15,16-octahydro-5,8,11,14,17-pentaoxabenzocyclopentadecen-2-yl)vinyl]-benzo[1,2-d;3,4-d']bisthiazole (hereafter, 1) gives efficient E --> Z photoisomerization (initial phi(trans --> cis) = 0.48), leading to lambda(exc)-dependent quasi-photostationary states composed primarily of E,Z and E,E isomer mixtures. Further irradiation gives [2 + 2]-cycloadducts of 1. In the presence of Ba2+ ions, essentially quantitative formation of 2:2 complexes, 1(2) x (Ba2+)2 controls the photochemical outcome. E --> Z photoisomerization of the ligand is entirely suppressed and efficient intramolecular [2 + 2]-photocycloaddition in the complexes leads to cyclobutane dimers of 1 (phiCB = 0.26). The reactivity of 1 in the presence of Mg2+ ions for which 1:2 complex formation dominates gives both cis-trans photoisomerization and enhanced photocycloaddition.     

Syntheses,crystal structures and thermoanalyses of alkaline earth metal complexes derived from dinitropyridone

Six new alkaline-earth metal compounds derived from dinitropyridone ligands (3,5-dinitropyrid-2-one, 2HDNP; 3,5-dinitropyrid-4-one, 4HDNP and 3,5-dinitropyrid-4-one-N-hydroxide, 4HDNPO) were synthesized and characterized by elemental analysis, FT-IR and partly by powder XRD, TG-DSC and X-ray single-crystal diffraction analysis. The structural determination revealed that one molecule of both magnesium salts (Mg(2DNP)₂ ·?8H₂O, (1), and Mg(4DNP)₂ ·?6H₂O (4)) comprise one cation [Mg(H₂O)₆]²⁺ and two anions displaying centro-symmetry with the Mg atom located at the center. Two anions (and crystalline water molecules) are joined by hydrogen bonds. The barium salt Ba(4DNP)₂ ·?4H₂O (5), is a centro-symmetric dimer with each Ba(II) being coordinated by one monodentate ligand anion, two bidentate ligand anions (different coordination pattern) and five water molecules. Another barium salt, Ba(4DNPO)₂ ·?6H₂O (6), is a coordination polymer, the ten-coordinate (BaO₁₀) barium environment comprising four water molecules, a pair of 4DNPOs via the pyridine-N-oxide oxygen, and one 4DNPOs from an adjacent metal atom offering chelating nitro group oxygen, bridging adjacent bariums. Abundant intermolecular hydrogen bonds link the molecules of each complex into multi-dimensional chains. The X-ray powder diffraction analysis confirmed the phase homogeneity of the polycrystalline samples. The TG-DSC results revealed that Mg(2DNP)₂ ·?8H₂O and Ba(4DNP)₂ ·?6H₂O each has three main weight-loss stages. The first step is the loss of all water molecules and the last step is the loss of the nitro groups and/or decomposition of the pyridine rings with the release of heat.     

Thermogravimetric investigation of the alkaline earth diliturates

Thermolysis curves for calcium, strontium and barium diliturates were obtained. Calcium dilituratc forms an octahydrate from aqueous solution while strontium, dilituratc forms a. heptahydrate and barium diliturate forms a tetrahydrate.Methods for the thermogravimetrie determination of strontium and barium were developed and found to be quite accurate; calcium can only be determined semi-qnartitatively by precipitation as the diliturate salt.     

Electrochromatography in the separation of ions: Separation of alkaline earth metals

Complete Separation of ternary mixtures of Ca, Mg and Sr or Ba ions with ammonium chloride and less complete but detectable separation of the same mixtures with ammonium nitrate have been achieved, as well as a few binary separations of the type Ca-Ba, Ca-Sr, Ca-Mg, Mg-Sr and Mg-Ba.     

Evaluation of alkali and alkaline earth metal cation selectivities of lariat ether amides by electrospray ionization mass spectrometry

Lariat ethers with pendant amide groups have shown promise as new ion sensors because of their selectivity towards particular metal ions. In this study we report alkali and alkaline earth metal binding selectivities of dibenzo-16-crown-5 and fifteen dibenzo-16-crown-5 lariat ether amides (LEAs) as determined by electrospray ionization mass spectrometry (ESI-MS). Additionally, the influence of the acid/base nature of the solution on metal cation selectivity is investigated. The validity of using ESI-MS for determination of selectivities is established by analogous experiments using hosts with known binding constants for the same metal cations and solvent systems. Collisionally activated dissociation (CAD) is used to evaluate the influence of the alkali metal cation binding on the fragmentation of the LEAs.     

Luminescence of vanadium and rare earth ions in alkaline earth sulfates

The luminescence of samples MeSO₄V, RE (Me = Mg, Ca, Ba) depends strongly on the nature of the Me ions. The amount of association of the V⁵⁺ and RE³⁺ ions can be estimated from the measured quantum efficiencies.     

Optimization of alkali-alkalkine earth cation separation on weak cation-exchangers

Summary The elution behavior of alkali and earth alkaline cations has been studied on a newly synthesized weak cationexchanger (WCX). Applying this stationary phase isocratic separation of these cations is possible. The dependence of retention on competing ion concentration is described via a simple model. The influence of crown ethers as well as organic eluent additives on selectivity and peak efficiency is demonstrated. With optimized separation such cations can be determined with detection limits of about 0.5 ppm using a conductivity detector without ion suppression.     

Cationic networks in the structures of rare earth germanates and borogermanates: Typology of cationic networks in the structures of rare earth compounds

The cationic networks in the structure of binary and mixed-anion compounds forming in the Ln₂O₃-B₂O₃-GeO₂ systems have been studied. The collection of the known cationic networks consisting of two dominating pure forms, anisotropic and isotropic, as well as of the combined anisotropic-isotropic and multivector variety of anisotropic cationic networks, was enlarged by two new types of isotropic cationic networks, namely, combined isotropic-isotropic (in the Nd₄GeO₈ structure) and imperfect isotropic (in the structure of borogermanates Ln₁₄ (BO₆)₆ (GeO₄)2O(₈).     

燃烧过程中碱/碱土金属对重金属迁移转化影响的研究进展

碱/碱土金属广泛存在于各种固体燃料中，在燃烧过程中碱/碱土金属与燃料中重金属及其他矿物发生复杂的物理化学反应，从而影响重金属的迁移和转化。本研究主要介绍了碱/碱土金属对As、Se、Pb和Cr四种重金属迁移转化的影响规律，包括碱金属和碱土金属对重金属迁移转化的影响，颗粒物团聚与黏结对重金属排放的影响三个方面。碱/碱土金属能够抑制重金属的挥发：碱金属与Cl元素的结合，降低了PbCl₂的生成；碱金属的存在有利于提升高岭土对Pb的吸附效率；碱/碱土金属可以与As和Se形成稳定的化合物。但同时需要注意碱/碱土金属与Cr的部分结合产物中，Cr以六价态存在，具有较高的毒性。碱/碱土金属对于团聚现象发生，分别起到了促进和抑制作用，适当含量的碱金属有利于减少重金属的释放。通过总结碱/碱土金属对重金属迁移转化的影响规律，以期为降低重金属的危害提供思路。     

Di-ionizable p-tert-butylcalix[4]arene-1,2-crown-5 and -crown-6 compounds in the cone conformation: synthesis and alkaline earth metal cation extraction

Di-ionizable p-tert-butylcalix[4]arene-1,2-crown-5 and -crown-6 ethers in the cone conformation were prepared and their conformations and regioselectivities were verified by NMR spectroscopy. The metal ion-complexing properties of these ligands were evaluated by competitive solvent extractions of alkaline earth metal cations from water into chloroform. The ligands were found to be efficient extractants with selectivity for Ba(2+). The maximal loadings were 95-100% as calculated for formation of 1 : 1 ionized ligand-metal ion complexes. With the variation of proton-ionizable groups, which were oxyacetic acid moieties and N-(X)sulfonyl oxyacetamide units with X = methyl, phenyl, 4-nitrophenyl, and trifluoromethyl, "tunable" acidity was obtained.