Covalent Stabilization of the Iridium-Containing Oxyhydrides SrMnIrOH and SrMnIrOH.

Reaction between SrMnIrO and CaH or LiH yields the iridium-containing oxyhydride phases SrMnIrOH or SrMnIrOH, respectively. Analysis of Mn K-edge XANES data indicate the presence of Ir centers in these oxyhydride phases, whose low-spin d configuration is consistent with the "covalent stabilization" of the metastable oxyhydride phases, as seen previously in analogous ruthenium and rhodium containing materials. Neutron powder diffraction data indicate the hydride ions are located exclusively within the "equatorial" anion sites of SrMnIrOH.

Competition between Anion-Deficient Oxide and Oxyhydride Phases during the Topochemical Reduction of LaSrCoRuO.

Binary metal hydrides can act as low-temperature reducing agents for complex oxides in the solid state, facilitating the synthesis of anion-deficient oxide or oxyhydride phases. The reaction of LaSrCoRuO, with CaH in a sealed tube yields the face-centered cubic phase LaSrCoRuOH. The reaction with LiH under similar conditions converts LaSrCoRuO to a mixture of tetragonal LaSrCoRuOH and cubic LaSrCoRuOH.

CCR2-dependent CX3CR1+ colonic macrophages promote dissemination.

Enterococci are common commensal bacteria that colonize the gastrointestinal tracts of most mammals, including humans. Importantly, these bacteria are one of the leading causes of nosocomial infections. This study examined the role of colonic macrophages in facilitating infections in mice.

Influence of Cation Substitution on Cycling Stability and Fe-Cation Migration in LiFeMTeO (M = Al, In) Cathode Materials.

LiFeTeO adopts a crystal structure, described in space group , related to that of LiSbO, in which Te, Fe, and Li cations reside in a partially ordered configuration within an hcp array of oxide ions. Chemical or electrochemical insertion of lithium is accompanied by a fully reversible migration of some of the Fe cations with an initial capacity of 120 mA h g (2.85 Li per formula unit).

Disproportionation of Co in the Topochemically Reduced Oxide LaSrCoRuO.

Complex transition-metal oxides exhibit a wide variety of chemical and physical properties which are a strong function the local electronic states of the transition-metal centres, as determined by a combination of metal oxidation state and local coordination environment. Topochemical reduction of the double perovskite oxide, LaSrCoRuO , using Zr, yields LaSrCoRuO . This reduced phase contains an ordered array of apex-linked square-based pyramidal Ru O , square-planar Co O and octahedral Co O units, consistent with the coordination-geometry driven disproportionation of Co .

CaMnOX (X = Cl, Br) Oxyhalides with 1-Dimensional Ferromagnetic Chains of Square-Planar S = 2 Mn.

Mixed anion oxyhalides with the formula CaMnOX (X = Cl, Br) are synthesized using solid-state reaction methods. These two materials crystallize in a novel structure type due to the small ionic radius of Ca and the strong Jahn-Teller effect of Mn. The resulting structure (space group ) contains one-dimensional chains of MnO square planes, with an angle of ∼120° between neighboring planes.

MnCaTaO-A Magnetically Ordered Polar Phase Prepared via Cation Exchange.

Reaction between the pseudo-Ruddlesden-Popper phase LiCaTaO and MnCl at 375 °C yields MnCaTaO, a paramagnetic polar phase (space group 2), which adopts an / distorted, layered perovskite structure. Magnetization and neutron diffraction data show that MnCaTaO adopts an antiferromagnetically ordered state below = 56 K and exhibits large lattice parameter anomalies and a transient increase in its polar distortion mode at = 50 K. However, in contrast to the related phase MnSrTaO, MnCaTaO shows no strong signature of weak ferromagnetism and thus shows no signs of magnetoelectric coupling.

Fluorochemicals from fluorspar via a phosphate-enabled mechanochemical process that bypasses HF.

All fluorochemicals-including elemental fluorine and nucleophilic, electrophilic, and radical fluorinating reagents-are prepared from hydrogen fluoride (HF). This highly toxic and corrosive gas is produced by the reaction of acid-grade fluorspar (>97% CaF) with sulfuric acid under harsh conditions. The use of fluorspar to produce fluorochemicals via a process that bypasses HF is highly desirable but remains an unsolved problem because of the prohibitive insolubility of CaF.

Complex Magnetic Order in Topochemically Reduced Rh(I)/Rh(III) LaMRhO (M = Co, Ni) Phases.

Topochemical reduction of the cation-disordered perovskite oxides LaCoRhO and LaNiRhO with Zr yields the partially anion-vacancy ordered phases LaCoRhO and LaNiRhO, respectively. Neutron diffraction and Hard X-ray photoelectron spectroscopy (HAXPES) measurements reveal that the anion-deficient phases contain Co/Ni and a 1:1 mixture of Rh and Rh cations within a disordered array of apex-linked MO square-planar and MO square-based pyramidal coordination sites. Neutron diffraction data indicate that LaCoRhO adopts a complex antiferromagnetic ground state, which is the sum of a C-type ordering (mM) of the -components of the Co spins and a G-type ordering (mΓ) of the -components of the Co spins.

The crystal and defect structures of polar KBiNbO.

KBiNbO was prepared from RbBiNbO by a sequence of cation exchange reactions which first convert RbBiNbO to LiBiNbO, before KBiNbO is formed by a further K-for-Li cation exchange. A combination of neutron, synchrotron X-ray and electron diffraction data reveal that KBiNbO adopts a polar, layered, perovskite structure (space group 11) in which the BiNbO layers are stacked in a (0, ½, ) arrangement, with the K cations located in half of the available 10-coordinate interlayer cation sites. The inversion symmetry of the phase is broken by a large displacement of the Bi cations parallel to the -axis.

The influence of the 6s configuration of Bi on the structures of A'BiNbO (A' = Rb, Na, Li) layered perovskite oxides.

Solid state compounds which exhibit non-centrosymmetric crystal structures are of great interest due to the physical properties they can exhibit. The 'hybrid improper' mechanism - in which two non-polar distortion modes couple to, and stabilize, a further polar distortion mode, yielding an acentric crystal structure - offers opportunities to prepare a range of novel non-centrosymmetric solids, but examples of compounds exhibiting acentric crystal structures stabilized by this mechanism are still relatively rare. Here we describe a series of bismuth-containing layered perovskite oxide phases, RbBiNbO, LiBiNbO and NaBiNbO, which have structural frameworks compatible with hybrid-improper ferroelectricity, but also contain Bi cations which are often observed to stabilize acentric crystal structures due to their 6s electronic configurations.

Hole and Electron Doping of Topochemically Reduced Ni(I)/Ru(II) Insulating Ferromagnetic Oxides.

LaSrNiRuO, LaSrNiRuO, and LaSrNiRuO are, respectively, the = ∞, 1, and 2 members of the (LaSr)Sr(NiRu)O compositional series. Reaction with CaH, in the case of the LaSrNiRuO perovskite phases, or Zr oxygen getters in the case of the LaSrNiRuO and LaSrNiRuO Ruddlesden-Popper phases, yields the corresponding topochemically reduced (LaSr)Sr(NiRu)O compounds (LaSrNiRuO, LaSrNiRuO, and LaSrNiRuO), which contain Ni and Ru cations in square-planar coordination sites. The = 1 members of each series (LaSrNiRuO, LaSrNiRuO, and LaSrNiRuO) exhibit insulating ferromagnetic behavior at low temperature, attributable to exchange couplings between the Ni and Ru centers they contain.

Directed synthesis of a hybrid improper magnetoelectric multiferroic material.

Preparing materials which simultaneously exhibit spontaneous magnetic and electrical polarisations is challenging as the electronic features which are typically used to stabilise each of these two polarisations in materials are contradictory. Here we show that by performing low-temperature cation-exchange reactions on a hybrid improper ferroelectric material, LiSrTaO, which adopts a polar structure due to a cooperative tilting of its constituent TaO octahedra rather than an electronically driven atom displacement, a paramagnetic polar phase, MnSrTaO, can be prepared. On cooling below 43 K the Mn centres in MnSrTaO adopt a canted antiferromagnetic state, with a small spontaneous magnetic moment.

LaSrCoRhO and LaSrNiRhO:Topochemically Reduced, Mixed Valence Rh(I)/Rh(III) Oxides.

Topochemical reduction of the = 1 Ruddlesden-Popper phases LaSrCoRhO and LaSrNiRhO with Zr yields LaSrCoRhO and LaSrNiRhO, respectively. Magnetization and XPS data reveal that while the rhodium centers in LaSrCoRhO and LaSrNiRhO have an average oxidation state of Rh, these are actually mixed valence Rh(I,III) compounds, with the disproportionation of Rh driven by the favorability of locating d Rh and d Rh cations within square-planar and square-based pyramidal coordination sites, respectively.

Structure and magnetism of the Rh-containing perovskite oxides LaSrMnRhO and LaSrFeRhO.

Synchrotron X-ray powder diffraction data indicate that La0.5Sr0.5Mn0.

Evidence of Paracrystalline Cation Order in the Ruddlesden-Popper Phase LaSrNiRuO through Neutron Total Scattering Techniques.

Cation ordering in perovskite-derived phases can lead to a wealth of tunable physical properties. Ordering is typically driven by a large difference between the cation size and charge, but many Ruddlesden-Popper phases ABO appear to lack such B-site ordering, even when these differences are present. One such example is the "double" Ruddlesden-Popper = 1 composition LaSrNiRuO.

A Structurally Characterized Cobalt(I) σ-Alkane Complex.

A cobalt σ-alkane complex, [Co(Cy P(CH ) PCy )(norbornane)][BAr ], was synthesized by a single-crystal to single-crystal solid/gas hydrogenation from a norbornadiene precursor, and its structure was determined by X-ray crystallography. Magnetic data show this complex to be a triplet. Periodic DFT and electronic structure analyses revealed weak C-H→Co σ-interactions, augmented by dispersive stabilization between the alkane ligand and the anion microenvironment.

Hole and Electron Doping of the 4d Transition-Metal Oxyhydride LaSr NiRuO H.

Hole or electron doping of phases prepared by topochemical reactions (e.g. anion deintercalation or anion-exchange) is extremely challenging as these low-temperature conversion reactions are typically very sensitive to the electron counts of precursor phases.

Pressure-Induced Transitions in the 1-Dimensional Vanadium Oxyhydrides SrVOH and SrVOH, and Comparison to 2-Dimensional SrVOH.

High-pressure X-ray diffraction measurements on the layered oxyhydrides SrVOH and SrVOH reveal that both compounds undergo a pressure-induced rock-salt to CsCl (1-2) structural transition, similar to those observed in binary compounds (oxides, halides, chalcogenides, etc.). This structural transition, observed at 43 and 45 GPa in SrVOH and SrVOH, respectively, relieves almost all of the accumulated strain on the infinite V-O-V ladders, such that the V-O bond lengths are almost identical at 0 and 50 GPa but are substantially compressed at intermediate pressures.

Exsolution of SrO during the Topochemical Conversion of LaSrCoRuO to the Oxyhydride LaSrCoRuOH.

 Reaction of the  = 1 Ruddlesden-Popper oxide LaSrCoRuO with CaH yields the oxyhydride phase LaSrCoRuOH via a topochemical anion exchange. Close inspection of the X-ray and neutron powder diffraction data in combination with HAADF-STEM images reveals that the nanoparticles of SrO are exsolved from the system during the reaction, with the change in cation stoichiometry accommodated by the inclusion of  > 1 (Co/Ru)OH "perovskite" layers into the Ruddlesden-Popper stacking sequence. This novel pseudotopochemical process offers a new route for the formation of > 1 Ruddlesden-Popper structured materials.

CaMnIrO: An Anion-Deficient Perovskite Oxide Containing Ir.

Reaction between CaMnIrO and NaH, either through solid-solid contact or via a gas mediated reaction process, yields the topochemically reduced phase CaMnIrO in which Mn and Ir cations are located within a partially anion-vacancy disordered lattice. Magnetization data from CaMnIrO can be fit by the Curie-Weiss law to yield C = 1.586 cm K mol and θ = -86.

Synthesis and Magnetism of Extended Solids Containing Transition-Metal Cations in Square-Planar, MO Coordination Sites.

With the exception of systems containing Cu, complex metal oxides containing paramagnetic transition-metal cations in square-planar coordination are rare. However, by either introducing chalcogenide, pnictide, or halide anions to form mixed-anion systems or by utilizing low-temperature topochemical reduction via anion deintercalation, an extensive range of phases containing square-planar MO units can be prepared. The crystal chemistry of a series of transition-metal AMOX oxyhalide and AMOBX oxychalcogenide and oxypnictide phases is reviewed along with how their magnetic behavior changes as a function of the transition-metal and electron count.

Structure and Magnetism of (La/Sr)MIrO and Topochemically Reduced (La/Sr)MIrO (M = Fe, Co) Complex Oxides.

Neutron powder diffraction data show that SrFeIrO, SrCoIrO, and LaSrCoIrO all adopt undistorted, n = 1 Ruddlesden-Popper structures in which the Ir and Fe/Co/Co cations are statistically disordered over all the octahedral coordination sites. Magnetization data indicate the two cobalt phases are spin glasses at low temperature, while SrFeIrO appears to adopt an antiferromagnetic state with very small magnetically ordered domains. Topochemical reduction with a Zr getter converts the tetragonal AMIrO phases to the corresponding orthorhombic AMIrO phases in which the Ir and Fe/Co/Co cations are located in approximately square-planar coordination sites.

Rhodium-containing oxide-hydrides: covalently stabilized mixed-anion solids.

The first rhodium-containing oxide-hydride phases, LaSrCo0.5Rh0.5O3H and La0.