DFT-calculated structures based on 1H NMR chemical shifts in solution vs. structures solved by single-crystal X-ray and crystalline-sponge methods: Assessing specific sources of discrepancies

DFT calculations of ¹H NMR chemical shifts, using various functionals and basis sets, the conductor-like polarizable continuum model and discrete solute-solvent hydrogen bond interactions have been used to derive the solution structures of methyl salicylate and methyl 2,5-dihydroxybenzoate. We demonstrate that very good agreement between experimental and computed ¹H NMR chemical shifts can be obtained for various basis sets. The DFT structures in solution were compared with the recently reported X-ray structure, solved by the crystalline-sponge method, of the methyl salicylate and the single-crystal X-ray structure of methyl 2,5-dihydroxybenzoate. It is demonstrated that the information provided by ¹H NMR chemical shifts about the solution structure is significantly more precise than that obtained by the single-crystal X-ray and the crystalline-sponge methods.     

A new uranyl niobate sheet in the cesium uranyl niobate Cs9[(UO2)8O4(NbO5)(Nb2O8)2]

A new cesium uranyl niobate, Cs₉[(UO₂)₈O₄(NbO₅)(Nb₂O₈)₂] or Cs₉U₈Nb₅O₄₁ has been synthesized by high-temperature solid-state reaction, using a mixture of U₃O₈, Cs₂CO₃ and Nb₂O₅. Single crystals were obtained by incongruent melting of a starting mixture with metallic ratio=Cs/U/Nb=1/1/1. The crystal structure of the title compound was determined from single crystal X-ray diffraction data, and solved in the monoclinic system with the following crystallographic data: a=16.729(2) Å, b=14.933(2) Å, c=20.155(2) Å β=110.59(1)°, P2₁/c space group and Z=4. The crystal structure was refined to agreement factors R₁=0.049 and wR₂=0.089, calculated for 4660 unique observed reflections with I?2σ(I), collected on a BRUKER AXS diffractometer with MoKα radiation and a CCD detector.In this structure the UO₇ uranyl pentagonal bipyramids are connected by sharing edges and corners to form a uranyl layer corresponding to a new anion-sheet topology, and creating triangular, rectangular and square vacant sites. The two last sites are occupied by Nb₂O₈ entities and NbO₅ square pyramids, respectively, to form infinite uranyl niobate sheets stacking along the [010] direction. The Nb₂O₈ entities result from two edge-shared NbO₅ square pyramids. The Cs⁺ cations are localized between layers and ensured the cohesion of the structure.The cesium cation mobility between the uranyl niobate sheets was studied by electrical measurements. The conductivity obeys the Arrhenius law in all the studied temperature domains. The observed low conductivity values with high activation energy may be explained by the strong connection of the Cs⁺ cations to the infinite uranyl niobate layers and by the high density of these cations in the interlayer space without vacant site.Infrared spectroscopy investigated at room temperature in the frequency range 400-4000 cm⁻¹, showed some characteristic bands of uranyl ion and niobium polyhedra.     

High-pressure single-crystal X-ray diffraction of Tl2SeO4

The effect of pressure on the crystal structure of thallium selenate (Tl₂SeO₄) (Pmcn, Z=4), containing the Tl⁺ cations with electron lone pairs, has been studied with single-crystal X-ray diffraction in a diamond anvil cell up to 3.64 GPa at room temperature. No phase transition has been observed. The compressibility data are fitted by a Murnaghan equation of state with the zero-pressure bulk modulus B₀=29(1) GPa and the unit-cell volume at ambient pressure V₀=529.6(8) Å³ (B′=4.00). Tl₂SeO₄ is the least compressible in the c direction, while the pressure-induced changes of the a and b lattice parameters are quite similar. These observations can be explained by different pressure effects on the nine- and 11-fold coordination polyhedra around the two non-equivalent Tl atoms. The SeO₄²⁻ tetrahedra are not rigid units and become more distorted. Their contribution to the compressibility is small. The effect of pressure on the isotypical oxide materials A₂TO₄ with the β-K₂SO₄ structure is discussed. It appears that the presence of electron lone pairs on the Tl⁺ cation does not seem to influence the compressibility of Tl₂SeO₄.     

Magnetism and Raman spectroscopy of the dimeric lanthanide iodates Ln(IO3)3 (Ln=Gd, Er) and magnetism of Yb(IO3)3

Colorless single crystals of Gd(IO₃)₃ or pale pink single crystals of Er(IO₃)₃ have been formed from the reaction of Gd metal with H₅IO₆ or Er metal with H₅IO₆ under hydrothermal reaction conditions at 180 °C. The structures of both materials adopt the Bi(IO₃)₃ structure type. Crystallographic data are (MoKα, λ=0.71073 Å): Gd(IO₃)₃, monoclinic, space group P2₁/n, a=8.7615(3) Å, b=5.9081(2) Å, c=15.1232(6) Å, β=96.980(1)°, V=777.03(5) Z=4, R(F)=1.68% for 119 parameters with 1930 reflections with I>2σ(I); Er(IO₃)₃, monoclinic, space group P2₁/n, a=8.6885(7) Å, b=5.9538(5) Å, c=14.9664(12) Å, β=97.054(1)°, V=768.4(1) Z=4, R(F)=2.26% for 119 parameters with 1894 reflections with I>2σ(I). In addition to structural studies, Gd(IO₃)₃, Er(IO₃)₃, and the isostructural Yb(IO₃)₃ were also characterized by Raman spectroscopy and magnetic property measurements. The results of the Raman studies indicated that the vibrational profiles are adequately sensitive to distinguish between the structures of the iodates reported here and other lanthanide iodate systems. The magnetic measurements indicate that only in Gd(IO₃)₃ did the 3+ lanthanide ion exhibit its full 7.9 μ_B Hund's rule moment; Er³⁺ and Yb³⁺ exhibited ground state moments and gap energy scales of 8.3 μ_B/70 K and 3.8 μ_B/160 K, respectively. Er(IO₃)₃ exhibited extremely weak ferromagnetic correlations (+0.4 K), while the magnetic ions in Gd(IO₃)₃ and Yb(IO₃)₃ were fully non-interacting within the resolution of our measurements (∼0.2 K).     

Macroscopic inhomogeneous deformation behavior arising in single crystal Ni–Mn–Ga foils under tensile loading

This study investigated macroscopic inhomogeneous deformation occurring in single-crystal Ni–Mn–Ga foils under uniaxial tensile loading. Two types of single-crystal Ni–Mn–Ga foil samples were examined as-received and after thermo-mechanical training. Local strain and the strain field were measured under tensile loading using laser speckle and digital image correlation. The as-received sample showed a strongly inhomogeneous strain field with intermittence under progressive deformation, but the trained sample result showed strain field homogeneity throughout the specimen surface. The as-received sample is a mainly polycrystalline-like state composed of the domain structure. The sample contains many domain boundaries and large domain structures in the body. Its structure would cause large local strain band nucleation with intermittence. However, the trained one is an ideal single-crystalline state with a transformation preferential orientation of variants after almost all domain boundary and large domain structures vanish during thermo-mechanical training. As a result, macroscopic homogeneous deformation occurs on the trained sample surface during deformation.     

光诱导转化法制备单晶Ag纳米三棱体和立方体

The preparation of Ag nanoparticles with the non-spherical shape has been conducted from aqueous solution by photo induced conversion. Ag nanoprisms (80～120nm) and nanocube s(90～200nm) were respectively obtained in the presence of trisodiumcitrate (TSC) orpolyvinylpirrolidon (PVP). These Ag nanoparticles were single-crystals. The results showed that Ag nanoprisms had apreferential growth direction along the Ag(111) axis and Ag nanocubes had a preferential growth direction along the Ag(100) axis. By means of characterization with TEM, ED and UV-V is Spectra, the fundamental analyses and discussion about the changing causes of nanoparticles shape from spherical tonon-spherical have been carried out in the photo induced process.     

铜纳米线的液相制备及其表面修饰研究进展

在现代纳米科学技术领域中,铜纳米线由于具有独特的光学、电学、力学和热学性质而成为制备透明柔性导电电极的优良材料。铜价格低廉,自然存储量较大,是实际应用中替代贵金属的理想材料。然而,将铜离子还原为单质铜比较困难,且单质铜非常容易被氧化,这成为应用中亟需解决的关键问题。如何制备单分散、稳定且具有抗氧化性的铜纳米线也成为该领域的研究热点。在各种制备铜纳米线的方法中,液相还原法不仅可以解决以上问题,且该方法具有制备条件限制少、成本低、简单易行等优点而被广泛应用于铜纳米线的大量合成。本文从铜纳米线的研究背景和研究价值入手,首先综述了不同（光滑或粗糙、单晶或孪晶）铜纳米线的液相制备方法及其生长机制。讨论了铜纳米线的氧化及其抗氧化表面包覆问题。最后对铜纳米线的研究意义和应用前景做出展望。     

Synthesis,characterization, and antibacterial evaluation of copper(II) complexes supported by phenylacetic acid derivatives,and diamine ligands

Four mixed-ligand complexes, [Cu₃(cpa)₆(pda)₁] (1) (cpa = 4-chlorophenylacetic acid, pda = 1,2-diaminopropane), [Cu₃(fpa)₆(tn)₁] (2) (fpa = 4-fluorophenylacetic acid, tn = 1,3-diaminopropane), [Cu₃(cpa)₆(en)₁] (3) (cpa = 4-chlorophenylacetic acid, en = ethylenediamine), and [Cu₃(fpa)₆(pda)₁] (4) (fpa = 4-fluorophenylacetic acid, pda = 1,2-diaminopropane), were synthesized by reacting 4-chlorophenylacetic acid or 4-fluorophenylacetic acid, the diamines, and metal salts. Their structures were determined by elemental analysis and single-crystal X-ray diffraction analysis. The antimicrobial activities for the metal complexes were evaluated against Escherichia coli, Pseudomonas putida, Bacillus subtilis, and Bacillus cereus. The antimicrobial results indicated that the four synthesized complexes displayed good inhibitory activity against E. coli and B. subtilis, and could be promising antibacterial agents.     

Effect of substitution and the counterion on the structural and spectroscopic properties of CuII complexes of methylated pyrazoles

The coordination chemistry of pyrazole and three of its methyl derivatives with the chloride and nitrate salts of copper(II) under strictly controlled reaction conditions is systematically explored to gain a better understanding of the effect of counterion coordination strength and ligand identity on the structure and electronic absorption spectra of their resulting complexes. Despite the initial 2 : 1 ligand to metal ratio in water, copper(II) nitrate forms exclusively 4 : 1 ligand to metal complexes while copper(II) chloride forms a 4 : 1 ligand to metal complex only with pyrazole, with the methyl derivatives forming 2 : 1 ligand to metal complexes, as determined by single-crystal X-ray diffraction (XRD). This is attributed to a combination of ligand sterics and stronger coordination of chloride relative to nitrate. Electronic absorption spectroscopy in both water and methanol reveals a surprisingly strong effect of the pyrazole methyl position on the Cu^II d–d transition, with 4-methylpyrazole producing a higher energy d–d transition relative to the other ligands studied. In addition, the number of methyl groups plays a determining role in the energy of the pz π→Cu^II d_xy LMCT band, lowering the transition energy as more methyl groups are added.