An atypical easy reductive cleavage of the conjugated CC bond in 1,1′-disubstituted isoindigos under the action of aqueous hydrazine hydrate

The reaction of diverse symmetrically-substituted isoindigo derivatives with 80% aqueous hydrazine hydrate is described. The influence of the structure of the substituent on either oxindole or isatin-3-hydrazone formation is discussed.     

Synthesis,X-ray crystal structure and electrochemical properties of (dithiolato)(diimine)copper(II) complexes: [Cu(mnt)(phen)] n and [Cu(dmit)(phen)] 2

Copper (II) complexes [Cu(dmit)(phen)]₂ (1) and [Cu(mnt)(phen)] _n (2) (mnt^2??=?maleonitriledithiolate, dmit^2??=?1,3-dithiole-2-thione-4,5-dithiolate, phen?=?1,10-phenanthroline) have been prepared by ligand-exchange between phen and [N(Bu)₄]₂[Cu(dmit)₂] or [N(Bu)₄]₂[Cu(mnt)₂]. Both complexes have been characterized by spectroscopic, electrochemical, and single-crystal X-ray analysis. In complex 1, dimers are extended into a two-dimensional array by weak S5–Cu contacts. In complex 2, monomers are extended into chains in a head-to-tail arrangement by weak Cu–S coordination bonds and π–π stacking interactions.     

Nickel deficiency in RENi2-xP2 (RE=La, Ce, Pr). Combined crystallographic and physical property studies

Large single crystals from RENi_2-xP₂ (RE=La, Ce, Pr) were synthesized from the pure elements using Sn as a metal flux, and their structures were established by X-ray crystallography. The title compounds were confirmed to crystallize in the body-centered tetragonal ThCr₂Si₂ structure type (space group I4/mmm (No. 139); Pearson's symbol tI10), but with a significant homogeneity range with respect to the transition metal. Systematic synthetic work, coupled with accurate structure refinements indicated strong correlation between the degree of Ni-deficiency and the reaction conditions. According to the temperature dependent dc magnetization measurements, LaNi_2-xP₂ (x=0.30(1)), as expected, is Pauli-like paramagnetic in the studied temperature regime, while the Ce-analog CeNi_2-xP₂ (x=0.28(1)) shows the characteristics of a mixed valent Ce³⁺/Ce⁴⁺ system with a possible Kondo temperature scale on the order of 1000 K. For three different PrNi_2-xP₂ (x?0.5) samples, the temperature and field dependence of the magnetization indicated typical local moment 4f-magnetism and a stable Pr³⁺ ground state, with subtle variations of T_C as a function of the concentration of Ni defects. Field-dependent heat capacity data for CeNi_2-xP₂ (x=0.28(1)) and PrNi_2-xP₂ (x=0.53(1)) are discussed as well.     

PrCo2Al8 and Pr2Co6Al19: Crystal structure and electronic properties

The praseodymium cobalt aluminides, PrCo₂Al₈ and Pr₂Co₆Al₁₉, were prepared by reaction of the elemental components in an arc-melting furnace, followed by heat treatment at 900 °C for several days. Their chemical composition was checked by scanning electron microscopy and energy dispersive spectroscopy, and their crystal structure was refined from single crystal X-ray diffraction data. PrCo₂Al₈ adopts the CaCo₂Al₈ type of structure, crystallizing with the orthorhombic space group Pbam, with four formula units in a cell of dimensions at room temperature: , , . Pr₂Co₆Al₁₉ crystallizes in the monoclinic space group C2/m, with four formula units in a cell of dimensions at room temperature: , , and β=103.903(1)°. Its structure belongs to the U₂Co₆Al₁₉ type. The crystal structures of both compounds studied can be viewed as three-dimensional structures resulting from the packing of Al polyhedra centred by the transition elements. Along the c-axis, the coordination polyhedra around the Pr atoms pack by face sharing to form strands, which are separated one from another by an extended Co-Al network. Magnetic measurements have revealed that PrCo₂Al₈ orders antiferromagnetically at , with a clear metamagnetic transition occurring at a critical field H_c=0.9(1) T. The temperature dependence of the susceptibility of Pr₂Co₆Al₁₉ does not provide any evidence for long-range magnetic ordering in the temperature domain 1.7-300 K. At low temperatures (T<10 K), the susceptibility saturates in a manner characteristic of a non-magnetic singlet ground state. At high temperatures, the magnetic susceptibility of each compound follows a Curie-Weiss law, with the effective magnetic moment per Pr atom of 3.48(5)μ_B and 3.41(2)μ_B for PrCo₂Al₈ and Pr₂Co₆Al₁₉, respectively. These values are close to the theoretical value of 3.58μ_B expected for a free Pr³⁺ ion and exclude any contribution due to the Co atoms. Both compounds exhibit in the temperature range 5-300 K metallic-like electrical conductivity, and their Seebeck coefficient is of the order of several μV/K.     

LiB3O5 crystal structure at 20, 227 and 377 °C

Crystal structure of LiB₃O₅ (a framework of [B₃O₅]⁻ rings and Li atoms located in interspaces) was refined at high temperatures using single-crystal X-ray diffraction, MoKα-radiation, anharmonic approximation, orthorhombic; Pna2₁; Z=4; 20 °C (a=8.444, b=7.378, c=5.146 Å, 1411 F(hkl), R=0.022); 227 °C (a=8.616, b=7.433, c=5.063 Å, 1336 F(hkl), R=0.026), 377 °C (a=8.746, b=7.480, c=5.013 Å, 1193 F(hkl), R=0.035). A high mobility of Li atoms and their highly asymmetric vibrations are revealed. Ellipsoid of Li thermal vibrations is oviform. Li is shifted on heating to 0.26 Å mainly along a-axis causing high thermal expansion in this direction; Li temperature factors are multiplied by 4 on heating. Rigid boron-oxygen groups in LiB₃O₅ remain practically stable on heating similar to α-Na₂B₈O₁₃ and α-CsB₅O₈. At the same time these groups rotate relative to each other like hinges leading to extremely anisotropic thermal expansion (α_a=101, α_b=31, α_c=−71, α_v=60×10⁻⁶ °C⁻¹, 20-530 °C, HTXRPD data).     

Synthesis, structure and two-photon absorption properties of a new multi-branched compound, 1,2,4,5-tetrakis(4-pyridylvinyl)benzene

A conjugated and symmetric multi-branched compound, 1,2,4,5-tetrakis(4-pyridylvinyl)benzene (TKPVB), has been synthesized and the crystal structures of TKPVB and its intermediate, 1,2,4,5-tetrakis(dimethoxyphosphorylmethyl)benzene, were determined by diffraction method. TKPVB with four units of 4-vinylpyridine moieties attached to the central benzene core presents an A-π-A general framework, where A is a π-deficient pyridine ring. The single-photon and two-photon absorption and fluorescence properties in different solvents of varying polarity have been investigated. It is also found that the one- and two-photon-induced fluorescence spectra are quite similar, which indicate that the one- and two-photon allowed-excited states are the same.     

Preparation and crystal structure of [Bi3I(C4H8O3H2)2(C4H8O3H)5]2Bi8I30 containing the novel polynuclear [Bi8I30] anion

Preparation and crystal structure of the novel compound [Bi₃I(C₄H₈O₃H₂)₂(C₄H₈O₃H)₅]₂Bi₈I₃₀ are reported. The title compound is prepared by heating of BiI₃ and diethylene glycol at 413 K in a sealed quartz glass tube filled with argon. Deep red single crystals are grown and applied to perform X-ray powder diffraction and X-ray single-crystal diffraction measurements. The compound crystallizes triclinic with space group P-1: Z=2, a=13.217(1) Å, b=15.277(1) Å, c=22.498(1) Å, α=84.33(1), β=73.18(1), γ=67.48(1). [Bi₃I(C₄H₈O₃H₂)₂(C₄H₈O₃H)₅]₂Bi₈I₃₀ comprises the novel polynuclear [Bi₈I₃₀]⁶⁻ anion and [Bi₃I(C₄H₈O₃H₂)₂(C₄H₈O₃H)₅]³⁺ as the cation. Cation as well as the anion can be assumed to represent intermediates between solid BiI₃ and BiI₃ completely dissolved in diethylene glycol.     

Crystal growth of a novel oxygen-deficient layered perovskite: Ba7Li3Ru4O20

Single crystals of both Ba₇Li₃Ru₄O₂₀ and Ba₄NaRu₃O₁₂ were grown from reactive molten hydroxide fluxes. Ba₇Li₃Ru₄O₂₀ is a 7L-layer perovskite-related phase resulting from the stacking of six [AO₃] layers and one oxygen deficient [AO₂] layer, thereby creating LiO₄ tetrahedra in addition to the LiO₆ octahedra and face-sharing Ru₂O₉ bi-octahedra formed from the [AO₃] layers. The compound crystallizes in the space group with a=5.7927(1) Å and c=50.336(2) Å, Z=3. Ba₄NaRu₃O₁₂ crystallizes in the space group P6₃mc with lattice parameters of a=5.8014(2) Å and c=19.2050(9) Å, Z=2. Ba₄NaRu₃O₁₂ is identical to a previously reported neutron refinement structure. The magnetic properties of Ba₇Li₃Ru₄O₂₀ are also reported.     

Synthesis, structure, and magnetism of Tb4PdGa12 and Tb4PtGa12

Single crystals of Tb₄MGa₁₂ (M=Pd, Pt) have been synthesized. The isostructural compounds crystallize in the cubic space group , with Z=2 and lattice parameters: a=8.5940(5) and 8.5850(3) Å for Tb₄PdGa₁₂ and Tb₄PtGa₁₂, respectively. The crystal structure consists of corner-sharing MGa₆ octahedra and TbGa₃ cuboctahedra. Magnetic measurements suggest that Tb₄PdGa₁₂ is an antiferromagnetic metamagnet with a Néel temperature of 16 K, while the Pt analog orders at T_N=12 K.     

Single-crystal high-nickel layered cathodes for lithium-ion batteries: advantages,mechanism, challenges and approaches

The ever-increasing demand of advanced lithium-ion batteries is calling for high-performance cathode materials. Among promising next-generation cathode materials, high-nickel layered oxides with spherical polycrystalline secondary particles exhibit the outstanding advantage of high energy density. However, polycrystals, suffered from the pulverization of particles and the expansion of cracks, show the shortcoming of poor cycling performance. As an efficient solution, the single-crystal route has been underestimated hitherto. Herein, the unique structural degradation mechanism of single crystals is emphasized, and their advantages against polycrystals are comprehensively summarized in terms of electrochemical, thermal, and mechanical properties. Furthermore, we point out the practical challenges of single-crystal materials toward practical applications and raise hopeful strategies for overcoming such issues. Based on the aforementioned characteristics and approaches, future directions are outlooked as well.