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Olivier SénèqueOlivia Reinaud 《Tetrahedron》2003,59(29):5563-5568
Eight novel calix[6]arene-based biomimetic ligands for transition metal ions have been synthesized. They display a non-symmetrical N3, N4 or N3ArO binding core that mimics enzyme active sites presenting histidine and tyrosine residues. The key step for their synthesis is the mono-alkylation at the small rim of the C3v symmetrical trimethyl ether derivative of tBu-calix[6]arene with N-Boc-2-chloroethylamine to yield a novel calix[6]arene synthon. Its combined O-alkylation with a chloromethyl aromatic amine and N-deprotection or alkylation or reductive alkylation with a salicylaldehyde derivative yielded the calix[6]arene-based ligands with mixed N/O donors. 相似文献
3.
A new 1,6-hexyldiamine heptaborate, [H3N(CH2)6NH3][B7O10(OH)3] (1), has been solvothermally synthesized and characterized by single-crystal X-ray diffraction, FTIR, elemental analysis, and thermogravimetric analysis. Compound 1 crystallizes in monoclinic system, space group P21/n with a=8.042(2) Å, b=20.004(4) Å, c=10.103(2) Å, and β=90.42(3)°. The anionic [B7O10(OH)3]n2n− layers are interlinked via hydrogen bonding to form a 3D supramolecular network containing large channels, in which the templated [H3N(CH2)6NH3]2+ cations are located. 相似文献
4.
A new compound, β-Ba3YB3O9, has been attained through solid phase transition from α-Ba3YB3O9 at high temperatures. Differential thermal analysis (DTA) revealed the phase transition at about 1120°C, the melting temperature at about 1253°C. Its crystal structure has been determined from powder X-ray diffraction data. The refinement was carried out using the Rietveld method and the final refinement converged with Rp=10.5% and Rwp=13.7%. This compound belongs to the hexagonal space group R-3, with lattice parameters a=13.0441(1) Å and c=9.5291(1) Å. There are 6 formulas per unit cell and 7 atoms in the asymmetric unit. The structure of β-Ba3YB3O9 is built up from Ba(Y)O8, BaO6 and YB6O18 units formed by one YO6 octahedron and six BO3 triangles with shared O atoms. 相似文献
5.
A systematic study of the chemical interaction of Ba2YCu3O6+y and Gd3NbO7 was conducted under two processing conditions: purified air (21% po2), and 100 Pa po2 (0.1% po2). Phases present along the pseudo-binary join Ba2YCu3O6z and Gd3NbO7 were found to be in two five-phase volumes within the system. Three common phases that are present in all samples are (Y,Gd)2Cu2O5, Ba(Y,Gd)2CuO5 and Cu2O or CuO (depending on the processing conditions). The assemblies of phases can be categorized in three regions, with Ba2YCu3O6+y: Gd3NbO7 ratios of (I)<5.5:4.5; (II)=5.5:4.5; and (III)>5.5:4.5. The lowest melting temperature of the system was determined to be ≈938 °C in air, and 850 °C at 100 Pa po2. Structure determinations of two selected phases, Ba2(GdxY1−x)NbO6 (Fm3¯m, No. 225), and (GdxY3−x)NbO7 (C2221, No. 20 and Ccmm, No. 63), were completed using the X-ray Rietveld refinement technique. Reference X-ray powder diffraction patterns for selected phases of Ba2(GdxY1−x)NbO6 (x=0.2, 0.4, 0.6, and 0.8) and (GdxY3−x)NbO7 (x=0.6, 1.2, 1.8, 2.4 and 3) have been prepared for inclusion in the Powder Diffraction File (PDF). 相似文献
6.
Mecheril V. Nandakumar 《Tetrahedron》2005,61(41):9775-9782
A Pd2dba3/P(i-BuNCH2CH2)3N catalyzed one-pot synthesis of unsymmetrically substituted trans-4-N,N-diarylaminostilbenes and both symmetrically and unsymmetrically substituted N,N-diarylaminostyrene derivatives is reported. The procedure involves two or more palladium catalyzed sequential coupling reactions (an amination and an inter-molecular Heck reaction) in one-pot using the same catalyst system with two different aryl halides, including aryl chlorides and hetero aryl halides as the coupling partners. 相似文献
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Oxides in the system PrCo1−xMgxO3 (x=0.0, 0.05, 0.10, 0.15, 0.20, 0.25) were synthesized by citrate technique and characterized by powder X-ray diffraction and scanning electron microscope. All compounds have a cubic perovskite structure (space group ). The maximum ratio of doped Mg in the system PrCo1−xMgxO3 is x=0.2. Further doping leads to the segregation of Pr6O11 in PrCo1−xMgxO3. The substitution of Mg for Co improves the performance of PrCoO3 as compared to the electrical conductivity measured by a four-probe electrical conductivity analyzer in the temperature range from 298 to 1073 K. The substitution of Mg for Co on the B site may be compensated by the formations of Co4+ and oxygen vacancies. The electrical conductivity of PrCo1−xMgxO3 oxides increases with increasing x in the range of 0.0-0.2. The increase in conductivity becomes considerable at the temperatures ?673 K especially for x?0.1; it reaches a maximum at x=0.2 and 1073 K. From x>0.2 the conductivity of PrCo1−xMgxO3 starts getting lower. This is probably a result of the segregation of Pr6O11 in PrCo1−xMgxO3 , which blocks oxygen transport, and association of oxygen vacancies. A change in activation energy for all PrCo1−xMgxO3 compounds (x=0-0.25) was observed, with a higher activation energy above 573 K and a lower activation energy below 573 K. The reasons for such a change are probably due to the change of dominant charge carriers from Co4+ to Vö in PrCo1−xMgxO3 oxides and a phase transition mainly starting at 573 K. 相似文献
8.
Magnetic diphase nanostructures of ZnFe2O4/γ-Fe2O3 were synthesized by a solvothermal method. The formation reactions were optimized by tuning the initial molar ratios of Fe/Zn. All samples were characterized by X-ray diffraction, thermogravimetric analysis, infrared spectroscopy, and Raman spectra. It is found that when the initial molar ratio of Fe/Zn is larger than 2, a diphase magnetic nanostructure of ZnFe2O4/γ-Fe2O3 was formed, in which the presence of ZnFe2O4 enhanced the thermal stability of γ-Fe2O3. Further increasing the initial molar ratio of Fe/Zn larger than 6 destabilized the diphase nanostructure and yielded traces of secondary phase α-Fe2O3. The grain surfaces of diphase nanostructure exhibited a spin-glass-like structure. At room temperature, all diphase nanostructures are superparamagnetic with saturation magnetization being increased with γ-Fe2O3 content. 相似文献
9.
We investigated the ammonolysis of β-Ga2O3 at elevated temperatures by means of ex situ X-ray diffraction, ex situ neutron diffraction and in situ X-ray absorption spectroscopy. Within the detection limits of these methods, we can rule out the existence of a crystalline or amorphous oxynitride phase that is not derived from wurtzite-type GaN. No evidence for a β-Ga2O3 related oxynitride phase was found, and the nitrogen solubility in β-Ga2O3 was found to be below the detection limit of about 2-3 at% in the anionic sublattice. These findings were obtained by monitoring the anionic occupancy factors and the lattice parameters of the β-Ga2O3 phase obtained from total diffraction pattern refinement with the Rietveld method and by linear combination fitting of the X-ray absorption spectra that were recorded during the ammonolysis. 相似文献
10.
Layered compounds have been synthesized and structurally characterized for the n=5 and 6 members of the perovskite-related family La4Srn−4TinO3n+2 by combining X-ray diffraction and transmission electron microscopy. Their structure can be regarded as comprising [(La,Sr)5Ti5O17] and [(La,Sr)6Ti6O20] perovskite blocks joined by crystallographic shears along the a-axis, with consecutive blocks shifted by 1/2 [100]p. The n=5 member is similar to the previously reported n=5 member of other AnBnO3n+2-related series. The n=6 member, which has only been briefly reported in other systems previously, is also a well-behaved member of this AnBnO3n+2 series. 相似文献
11.
Masaoki Oku Toetsu Shishido Takeshi Shinohara Qiang Sun Yoshiyuki Kawazoe Kazuo Nakajima Kazuaki Wagatsuma 《Journal of solid state chemistry》2004,177(2):457-460
The solid solutions of ScBRh3-ScRh3 and CeBRh3-CeRh3 are synthesized by the arc melting method, where RBRh3 and RRh3 (R=rare earth element) have perovskite and AuCu3 type structures, respectively. The binding energy of Sc 2p3/2 for ScBxRh3 increases with the boron concentration. The Knight shift of 45Sc observed by nuclear magnetic resonance spectroscopy decreases with increase of boron concentration. The decrement of the Knight shift corresponds the Sc 4s electron density at the Fermi level. The intensity ratio of f2: f1: f0 of Ce 3d XPS spectrum changes with boron concentration of CeBxRh3. It is concluded that in both cases of ScBxRh3 and CeBxRh3 the charge on the atoms on A-site changes with the concentration of the atoms on B-site, where the atoms are not directly bound. 相似文献
12.
Single crystals of the new compounds TM2Cu3Ga8 (TM=V, Mo, W) were synthesised from the elements. Structure determinations of the isotypic compounds (cI104, space group , Z=8; Mo2Cu3Ga8: a=11.9171(10) Å, 613 refl., 23 param., R1(F)=0.022, wR2(F2)=0.047; W2Cu3Ga8: 11.9248(8) Å, 346 refl., 23 param., R1(F)=0.048, wR2(F2)=0.086; V2Cu3Ga8: 11.7861(14) Å, 374 refl., 24 param., R1(F)=0.033, wR2(F2)=0.081) showed a new cubic structure type which can be classified as an ordered defect variant of a bcc packing with a′=4a: [(TM)2(Cu)3(□)3][Ga8]. The coordination polyhedra of the transition metals consist of Ga8-cubes with 3 sides capped by Cu leading to coordination number 11. The arrangement of the TMGa8Cu3-polyhedra is in a way they form itself a 3-fold capped cube. All compositions were confirmed by EDX measurements. 相似文献
13.
Zuoliang Liu Guochun Zhang Jianxiu Zhang Peizhen Fu 《Journal of solid state chemistry》2010,183(6):1437-1441
Using Na2CO3-H3BO3-NaF as fluxes, transparent RE:Na3La9O3(BO3)8 (abbr. RE:NLBO, RE=Er, Yb) crystals have been grown by the top seed solution growth (TSSG) method. The X-ray powder diffraction analysis shows that the RE:NLBO crystals have the same structure with NLBO. The element contents were determined by molar to be 0.64% Er3+ in Er:NLBO, 2.70% Yb3+ in Yb:NLBO, respectively. The polarized absorption spectra of RE:NLBO have been measured at room temperature and show that both Er:NLBO and Yb:NLBO have a strong absorption bands near 980 nm with wide FWHM (Full Wave at Half Maximum) (21 nm for Er:NLBO and 25 nm for Yb:NLBO). Fluorescence spectra have been recorded. Yb:NLBO has the emission peaks at 985 nm, 1028 nm and 1079 nm and the emission peak of Er:NLBO is at 1536 nm. Spectral parameters have been calculated by the Judd-Ofelt theory for Er:NLBO and the reciprocity method for Yb:NLBO, respectively. The calculated values show that Er:NLBO is a candidate of 1.55 μm laser crystals and Yb:NLBO is a candidate for self-frequency doubling crystal. 相似文献
14.
Jens-Erik Jørgensen Lene Mosegaard Torben R. Jensen 《Journal of solid state chemistry》2007,180(1):180-185
The formation of maghemite, γ-Fe2O3 nanoparticles has been studied by in situ X-ray powder diffraction. The maghemite was formed by thermal decomposition of an amorphous precursor compound made by reacting lauric acid, CH3(CH2)10COOH with Fe(NO3)3·9H2O. It has been shown that cubic γ-Fe2O3 was formed directly from the amorphous precursor and that vacancy ordering starts about 45 min later at 305 °C resulting in a tripled unit cell along the c-axis. The kinetics of grain growth was found to obey a power law with growth exponents n equal to 0.136(6) and 0.103(5) at 305 and 340 °C, respectively. Particles with average sizes of 12 and 13 nm were obtained in 86 and 76 min at 305 and 340 °C, respectively. The structure of cubic and vacancy ordered phases of γ-Fe2O3 was studied at 305 °C by Rietveld refinements. 相似文献
15.
Xiaole Weng Paul Boldrin Isaac Abrahams Suela Kellici 《Journal of solid state chemistry》2008,181(5):1123-1132
A new direct route for the “bottom up” syntheses of phases in the Lan+1NinO3n+1 series (n=1, 2, 3 and ∞) has been achieved via single-step heat treatments of nanosized co-crystallized precursors. The co-crystallized precursors were prepared using a continuous hydrothermal flow synthesis system that uses a superheated water flow at ca. 400 °C and 24.1 MPa to produce nanoparticulate slurries. Overall, a significant reduction in time and number of steps for the syntheses of La3Ni2O7 and La4Ni3O10 was achieved compared with more conventional synthesis methods, which typically require multiple homogenization and reheating steps over several days. 相似文献
16.
Ivan V. Ogorodnyk Igor V. Zatovsky Vyacheslav N. Baumer 《Journal of solid state chemistry》2006,179(11):3461-3466
New complex phosphates of the general formula K2M0.5Ti1.5(PO4)3 (M=Mn, Co) have been obtained from the melting mixture of KPO3, K4P2O7, TiO2 and CoCO3·mCo(OH)2 or Mn(H2PO4)2 by means of a flux technique. The synthesized phosphates have been characterized by the single-crystal X-ray diffraction and the FTIR-spectroscopy. The compounds crystallize in the cubic system with the space group P213 and cell parameters a=9.9030(14) Å for K2Mn0.5Ti1.5(PO4)3 and a=9.8445(12) Å for K2Co0.5Ti1.5(PO4)3. Both phosphates are isostructural with the langbeinite mineral and contain four formula unit K2M0.5Ti1.5(PO4)3 per unit cell. The structure can be described using [M2(PO4)3] framework composed of two [MO6] octahedra interlinked via three [PO4] tetrahedra. The Curie-Weiss-type behavior is observed in the magnetic susceptibility. 相似文献
17.
Diol capped γ-Fe2O3 nanoparticles are prepared from ferric nitrate by refluxing in 1,4-butanediol (9.5 nm) and 1,5-pentanediol (15 nm) and uncapped particles are prepared by refluxing in 1,2-propanediol followed by sintering the alkoxide formed. X-ray diffraction (XRD) shows that all the samples have the spinel phase. Raman spectroscopy shows that the samples prepared in 1,4-butanediol and 1,5-pentanediol and 1,2-propanediol (sintered at 573 and 673 K) are γ-Fe2O3 and the 773 K-sintered sample is Fe3O4. Raman laser studies carried out at various laser powers show that all the samples undergo laser-induced degradation to α-Fe2O3 at higher laser power. The capped samples are however, found more stable to degradation than the uncapped samples. The stability of γ-Fe2O3 sample with large particle size (15.4 nm) is more than the sample with small particle size (10.2 nm). Fe3O4 having a particle size of 48 nm is however less stable than the smaller γ-Fe2O3 nanoparticles. 相似文献
18.
Hyunsoo Park 《Journal of solid state chemistry》2004,177(1):159-164
The compound previously reported as Ba2Ti2B2O9 has been reformulated as Ba3Ti3B2O12, or Ba3Ti3O6(BO3)2, a new barium titanium oxoborate. Small single crystals have been recovered from a melt with a composition of BaTiO3:BaTiB2O6 (molar ratio) cooled between 1100°C and 850°C. The crystal structure has been determined by X-ray diffraction: hexagonal system, non-centrosymmetric space group, a=8.7377(11) Å, c=3.9147(8) Å, Z=1, wR(F2)=0.039 for 504 unique reflections. Ba3Ti3O6(BO3)2 is isostructural with K3Ta3O6(BO3)2. Preliminary measurements of nonlinear optical properties on microcrystalline samples show that the second harmonic generation efficiency of Ba3Ti3O6(BO3)2 is equal to 95% of that of LiNbO3. 相似文献
19.
J.L. Cui W.J. Xiu L.D. Mao P.Z. Ying X. Qian 《Journal of solid state chemistry》2007,180(3):1158-1162
Ag-doped n-type (Bi2Te3)0.9-(Bi2−xAgxSe3)0.1 (x=0-0.4) alloys were prepared by spark plasma sintering and their physical properties evaluated. When at low Ag content (x=0.05), the temperature dependence of the lattice thermal conductivity follows the trend of (Bi2Te3)0.9-(Bi2Se3)0.1; while at higher Ag content, a relatively rapid reduction above 400 K can be observed due possibly to the enhancement of scattering of phonons by the increased defects. The Seebeck coefficient increases with Ag content, with some loss of electrical conductivity, but the maximum dimensionless figure of merit ZT can be obtained to be 0.86 for the alloy with x=0.4 at 505 K, about 0.2 higher than that of the alloy (Bi2Te3)0.9-(Bi2Se3)0.1 without Ag-doping. 相似文献
20.
Sylvie Daviero-Minaud Chanapa Kongmark Rose-Noëlle Vannier 《Journal of solid state chemistry》2009,182(2):289-294
The actual oxygen environment of the tungsten dopant in the Ba2In2−xWxO5+3x/2 solid solution was revealed by combining X-ray absorption spectroscopy at the tungsten LI and LIII edges and at the indium LI edge. Whatever the substitution ratio, the tungsten atoms exhibit a regular octahedral environment. When the substitution ratio increases, the oxygen vacancies are progressively filled until their total occupancy for x=2/3. For x?0.3, the perovskite structure is stabilised; the tungsten atoms are randomly distributed in the structure. Although X-ray diffraction revealed a cubic symmetry for these compositions, a local distortion of the indium environment is observed when a tungsten atom is in its surrounding. 相似文献