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91.
Guennic BL Petit S Chastanet G Pilet G Luneau D Amor NB Robert V 《Inorganic chemistry》2008,47(2):572-577
We report the synthesis and structural and magnetic characterization of an original Cu(3) oxidase model. The Schiff base ligand used in the synthesis derives from condensation of acetylacetone with glycine amino acid. The K[Cu(3)(L)(3)(micro(3)-OH)].(H(2)O)(2) complex crystallizes at room temperature in the tetragonal P43212 space group with a = 20.540(3) A and c = 15.866(6) A and consists of triangular Cu(3) units. The magnetic behavior interpretation suggests the presence of spin frustration, which has been investigated by means of ab initio DDCI calculations. It is shown that the system should be viewed as a "ménage à trois" spin-coupled pattern mediated by a central hydroxo group, lifting the doublet degeneracy by approximately 8 cm-1. 相似文献
92.
Anica?Weller Enrique?Javier?Carrasco-Correa Carolina?Belenguer-Sapi?a Adela?de los?Reyes Mauri-Aucejo Pedro?Amorós José?Manuel?Herrero-MartínezEmail author 《Mikrochimica acta》2017,184(10):3799-3808
Monolithic stationary phases for use in capillary electrochromatography were prepared by incorporation of mesoporous silica particles (of type MCM-41 or UVM-7) in a polymer obtained from butyl methacrylate and ethylene glycol dimethacrylate as monomers, 1,4-butanediol and 1-propanol as porogen, and azobisisobutyronitrile as initiator. The stability of the dispersions with varying fractions of silica particles was investigated by UV-vis spectrometry. Using continuous stirring during the capillary filling and short UV-polymerization times, polymeric beds with homogenously dispersed mesoporous particles (with contents up to 35 wt% of silica) are obtained. The resulting hybrid monolithic columns were characterized using scanning electron microscopy. The chromatographic performance of these novel stationary phases was evaluated by using alkyl benzenes and benzoic acid derivatives as test analytes. The use of these polymers leads to increased retention and separation efficiency compared to the parent monolith. The column efficiency reached values of up to 140,000 plates m?1. The resulting hybrid monolithic columns also exhibited a satisfactory reproducibility with relative standard deviations of ca. 14% (batch-to-batch). 相似文献
93.
Investigation of the Crystal Structure,Characterization, Hirshfeld Surface,and Theoretical Study of (C6H14N)5[HP2Mo5O23]·4H2O 下载免费PDF全文
The synthesis of an organoammonium diphosphopentamolybdates(VI), (C6H14N)5[HP2Mo5O23] · 4H2O ( 1 ), is reportet. The molecular structure and spectroscopic analysis were performed using experimental techniques like X‐ray diffraction, FT‐IR, and UV/Vis. The single crystal analysis of the title compound shows that the compound crystallizes in the monoclinic crystal system with space group P21/c and cell constants of a = 12.7934(2) Å, b = 14.8145(2) Å, c = 27.2637(5) Å, and β = 92.9298(14)°. The Hirshfeld surfaces and the associated 2D fingerprint plots were investigated to study the intermolecular interactions in the crystal packing and this study has confirmed that the hydrogen bonding interactions play a dominating role in the stability of crystal structure. The theoretical calculations were done using PM3 semi‐empirical model and several properties were studied. 相似文献
94.
95.
The effects of temperature, organic modifier and the type of acid on the retention factor, the resolution and peak shape of betamethasone and dexamethasone are described. The study is performed using narrow bore porous graphitic carbon (PGC) columns online with diode-array detector (DAD) and ESI MS/MS. The results show that temperature affects the retention behaviour of the two compounds and ACN yields the best separation while no effect is obtained by changing the type of organic acid. The developed method is applied for the confirmation of dexamethasone and betamethasone in human urine. 相似文献
96.
An organic–inorganic hybrid material based on paradodecatungstate building blocks and sodium–aminoacetic acid complex subunits,{Na10(H3N–CH2–COO)2[H2W12O42]}·28H2O (1), have been synthesized under mildly acidic conditions. This compound was characterized by single-crystal X-ray diffraction, elemental analysis, IR and UV–visible spectroscopies, and cyclic voltammetry. The compound crystallizes in the triclinic space group P-1 with a = 11.879(2) Å, b = 12.706(2) Å, c = 13.067(2) Å, α = 74.11(3)°, β = 79.71(3)°, γ = 65.95(3)°, V = 1727.2(5) Å3, and Z = 1. The crystal structure consists of infinite 2D layers constructed from [H2W12O42]10? clusters and sodium–aminoacetic acid complexes; adjacent layers are further joined by the complex units and sodium cations to yield a three-dimensional network. 相似文献
97.
A method for the generation of transition metal-phosphorus multiple bonds has been developed using the reactions of a novel thiophosphinidene-bridged dimolybdenum complex with different metal carbonyls. The overall process could be considered as a transmetalation of the phosphinidene ligand involving the activation of P-S and P-Mo bonds. 相似文献
98.
Electrical properties of ferroelectric BiMnO3–PbTiO3 under tailored synthesis and ceramic processing
Conductivity is a main issue in research on multiferroic perovskite oxides, which makes the characterization of their ferroelectric properties difficult, and for several compounds even to unambiguously state their ferroelectric nature. In this report, we use ferroelectric BiMnO3–PbTiO3 as a model system to study the relationships among synthesis, processing, and conductivity in ABO3 perovskite oxides with magnetically active cations in the B-site. Three single phase, dense ceramic materials processed by conventional sintering, hot pressing, or spark plasma sintering (SPS) of powders synthesized by either wet chemistry or mechanochemical activation were studied. Impedance spectroscopy analysis was carried out to obtain grain and grain boundary conductivities for the three materials, along with activation energies. Mechanosynthesis is shown not to modify the mechanism of bulk or boundary conductivity, but only the carrier concentration, while SPS processing results in a low temperature, additional conduction mechanism. 相似文献
99.
Fethi Ben Amor 《代数通讯》2013,41(3):1118-1134
We study orthogonally additive homogeneous polynomials on a uniformly complete vector lattice taking values either in a separated bornological vector space or in a separated topological vector space. This study is based on the notions of orthosymmetric multilinear maps and vector lattice powers. 相似文献
100.
Ferrando-Soria J Ruiz-García R Cano J Stiriba SE Vallejo J Castro I Julve M Lloret F Amorós P Pasán J Ruiz-Pérez C Journaux Y Pardo E 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(6):1608-1617
The concept of "molecular magnetic sponges" was introduced for the first time in 1999 by the creative imagination of the late Olivier Kahn. It refers to the exotic spongelike behavior of certain molecule-based materials that undergo a dramatic change of their magnetic properties upon reversible dehydration/rehydration processes. Here we report a unique example of a manganese(II)-copper(II) mixed-metal-organic framework of formula [Na(H(2)O)(4)](4)[Mn(4){Cu(2)(mpba)(2)(H(2)O)(4)}(3)]·56.5H(2)O (1) (mpba=N,N'-1,3-phenylenebis(oxamate)). Compound 1 possesses a 3D Mn(II)(4)Cu(II)(6) pillared layer structure with mixed square and octagonal pores of approximate dimensions 1.2×1.2 nm and 2.1×3.0 nm, respectively, hosting a large amount of crystallization H(2)O molecules and hydrated Na(I) countercations as guests. It reversibly switches from a crystalline hydrated phase with long-range ferromagnetic ordering at a rather high critical temperature (T(c)) of 22.5 K to an amorphous dehydrated phase with T(c) as low as 2.3 K, which is accompanied by a breathing-type dynamic effect involving a large crystal volume (ca. 45%) and color changes after water desorption/adsorption. The combination of both the open-framework structure and the spongelike optical, mechanical, and magnetic switching behavior in this new class of oxamato-based porous magnets offers fascinating possibilities in designing multifunctional materials for host-guest molecular sensing. 相似文献