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Floating Zone Growth of Pure and Pb-Doped Bi-2201 Crystals
In this review, we summarize recent progress in crystal growth and understanding of the influence of crystal structure on superconductivity in pure and Pb-doped Bi2Sr2CuOy (Bi-2201) materials belonging to the overdoped region of high-temperature cuprate superconductors. The crystal growth of Bi-2201 superconductors faces challenges due to intricate materials chemistry and the lack of knowledge of corresponding phase diagrams. Historically, a crucible-free floating zone method emerged as the most promising growth approach for these materials, resulting in high-quality single crystals. This review outlines the described methods in the literature and the authors’ synthesis endeavors encompassing Pb-doped Bi-2201 crystals, provides a detailed structural characterization of as-grown and post-growth annealed samples, and highlights optimal growth conditions that yield large-size, single-phase, and compositionally homogeneous Bi-2201 single crystals.
The Contrasting Character of Early and Late Transition Metal Fluorides as Hydrogen Bond Acceptors
The association constants and enthalpies for the binding of hydrogen bond donors to group 10 transition metal complexes featuring a single fluoride ligand (trans-[Ni(F)(2-C5NF4)(PR3)2], R = Et 1a, Cy 1b, trans-[Pd(F)(4-C5NF4)(PCy3)2] 2, trans-[Pt(F){2-C5NF2H(CF3)}(PCy3)2] 3 and of group 4 difluorides (Cp2MF2, M = Ti 4a, Zr 5a, Hf 6a; Cp*2MF2, M = Ti 4b, Zr 5b, Hf 6b) are reported. These measurements allow placement of these fluoride ligands on the scales of organic H-bond acceptor strength. The H-bond acceptor capability β (Hunter scale) for the group 10 metal fluorides is far greater (1a 12.1, 1b 9.7, 2 11.6, 3 11.0) than that for group 4 metal fluorides (4a 5.8, 5a 4.7, 6a 4.7, 4b 6.9, 5b 5.6, 6b 5.4), demonstrating that the group 10 fluorides are comparable to the strongest organic H-bond acceptors, such as Me3NO, whereas group 4 fluorides fall in the same range as N-bases aniline through pyridine. Additionally, the measurement of the binding enthalpy of 4-fluorophenol to 1a in carbon tetrachloride (−23.5 ± 0.3 kJ mol–1) interlocks our study with Laurence’s scale of H-bond basicity of organic molecules. The much greater polarity of group 10 metal fluorides than that of the group 4 metal fluorides is consistent with the importance of pπ–dπ bonding in the latter. The polarity of the group 10 metal fluorides indicates their potential as building blocks for hydrogen-bonded assemblies. The synthesis of trans-[Ni(F){2-C5NF3(NH2)}(PEt3)2], which exhibits an extended chain structure assembled by hydrogen bonds between the amine and metal-fluoride groups, confirms this hypothesis.
Tetracarbonyl[N-(diphenylphosphanyl-κP)-N,N′-diisopropyl-P-phenylphosphorus diamide-κP]molybdenum(0) with an unknown solvent
The title complex, [Mo(C24H30N2P2)(CO)4], contains a molybdenum centre bearing a P,P′-cis-chelating Ph2PN(iPr)P(Ph)NH(iPr) and four carbonyl ligands in a distorted octahedral coordination geometry. This results in a nearly planar four-membered metallacycle. In the crystal, molecules are linked by N—H...O and C—H...O hydrogen bonds to form layers parallel to the ac plane. For the final refinement, the contributions of disordered solvent molecules were removed from the diffraction data with SQUEEZE in PLATON [Spek (2015). Acta Cryst. C71, 9–18]. The given chemical formula and other crystal data do not take into account the unknown solvent molecule(s).
Tetracarbonyl[4,4-dimethyl-2-(pyridin-2-yl)-2-oxazoline-κ2N,N′]molybdenum(0)
In the title compound, [Mo(C10H12N2O)(CO)4], the molybdenum(0) center is surrounded by a bidentate diimine [4,4-dimethyl-2-(pyridin-2-yl)-2-oxazoline] and four carbonyl ligands in a distorted octahedral coordination geometry. The diimine ligand coordinates via the two nitrogen atoms.
Enantio- and diastereoselective synthesis of γ-amino alcohols
The γ-amino alcohol structural motif is often encountered in drugs and natural products. We developed two complementary catalytic diastereoselective methods for the synthesis of N-PMP-protected γ-amino alcohols from the corresponding ketones. The anti-products were obtained through Ir-catalyzed asymmetric transfer hydrogenation, the syn-products via Rh-catalyzed asymmetric hydrogenation.
Tetracarbonyl-2κ4C-[μ-5-methyl-1,1,3-triphenyl-2-(propan-2-yl)-2,4-diaza-1,3-diphosphahexan-4-ido-1κN4:2κP1,P3](N,N,N′,N′-tetramethylethane-1,2-diamine-1κ2N,N′)lithiummolybdenum
The title complex, [LiMo(C6H16N2)(C24H29N2P2)(CO)4], contains a distorted octahedrally coordinated molybdenum centre bearing a lithiated P,P′-cis-chelating PNPN ligand, which results in a nearly planar four-membered metallacycle. The Li atom is coordinated by one equivalent tetramethylethylenediamine. In the crystal, molecules are linked via weak C—H...O interactions, forming a chain along the b-axis direction.
The Weak 3D Topological Insulator Bi12Rh3Sn3I9
Topological insulators (TIs) gained high interest due to their protected electronic surface states that allow dissipation-free electron and information transport. In consequence, TIs are recommended as materials for spintronics and quantum computing. Yet, the number of well-characterized TIs is rather limited. To contribute to this field of research, we focused on new bismuth-based subiodides and recently succeeded in synthesizing a new compound Bi12Rh3Sn3I9, which is structurally closely related to Bi14Rh3I9 – a stable, layered material. In fact, Bi14Rh3I9 is the first experimentally supported weak 3D TI. Both structures are composed of well-defined intermetallic layers of ∞2[(Bi4Rh)3I]2+ with topologically protected electronic edge-states. The fundamental difference between Bi14Rh3I9 and Bi12Rh3Sn3I9 lies in the composition and the arrangement of the anionic spacer. While the intermetallic 2D TI layers in Bi14Rh3I9 are isolated by ∞1[Bi2I8]2− chains, the isoelectronic substitution of bismuth(III) with tin(II) leads to ∞2[Sn3I8]2− layers as anionic spacers. First transport experiments support the 2D character of this material class and revealed metallic conductivity. © 2020 The Authors. Published by Wiley-VCH GmbH
Enantiomer-selective magnetization of conglomerates for quantitative chiral separation
Selective crystallization represents one of the most economical and convenient methods to provide large-scale optically pure chiral compounds. Although significant development has been achieved since Pasteur’s separation of sodium ammonium tartrate in 1848, this method is still fundamentally low efficient (low transformation ratio or high labor). Herein, we describe an enantiomer-selective-magnetization strategy for quantitatively separating the crystals of conglomerates by using a kind of magnetic nano-splitters. These nano-splitters would be selectively wrapped into the S-crystals, leading to the formation of the crystals with different physical properties from that of R-crystals. As a result of efficient separation under magnetic field, high purity chiral compounds (99.2 ee% for R-crystals, 95.0 ee% for S-crystals) can be obtained in a simple one-step crystallization process with a high separation yield (95.1%). Moreover, the nano-splitters show expandability and excellent recyclability. We foresee their great potential in developing chiral separation methods used on different scales. © 2019, The Author(s).
3,3′-Dimethyl-1,1′-methylenediimidazolium tetrabromidocobaltate(II)
The title compound, (C9H14N4)[CoBr4], was obtained as single crystals directly in very low yield as a side product in the reaction of 1,1′-bis(1-methylimidazolium)acetate bromide and CoBr2. The title compound consists of an imidazolium-based dication and a tetrabromidocobaltate(II) complex anion, which are connected via C—H...Br interactions in the crystal. The dihedral angle between the imidazolium rings in the cation is 72.89 (16)°. The CoII ion in the anion is coordinated tetrahedrally by four bromide ligands [Co—Br = 2.4025 (5)–2.4091 (5) Å and Br—Co—Br = 106.224 (17)–113.893 (17)°]. The compound exhibits a high melting point (>300°C) and is a light-blue solid under ambient conditions.