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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Reactivity of Silanes with ( tBu PONOP)Ruthenium Dichloride: Facile Synthesis of Chloro-Silyl Ruthenium Compounds and Formic Acid Decomposition

The coordination of tBu PONOP ( tBu PONOP=2,6-bis(ditert-butylphosphinito)pyridine) to different ruthenium starting materials, to generate ( tBu PONOP)RuCl 2 , was investigated in this paper. The resultant ( tBu PONOP)RuCl 2 reactivity with three different silanes was then investigated and contrasted dramatically with the reactivity of ( iPr PONOP)RuCl 2 (DMSO) ( iPr PONOP=2,6-bis(diisopropylphosphinito)pyridine) with the same silanes. The 16-electron species ( tBu PONOP)Ru(H)Cl was produced from the reaction of triethylsilane with ( tBu PONOP)RuCl 2 . Reactions of ( tBu PONOP)RuCl 2 with both phenylsilane or diphenylsilane afforded the 16-electron hydrido-silyl species ( tBu PONOP)Ru(H)(PhSiCl 2 ) and ( tBu PONOP)Ru(H)(Ph 2 SiCl), respectively. Reactions of all three of these complexes with silver triflate afforded the simple salt metathesis products of ( tBu PONOP)Ru(H)(OTf), ( tBu PONOP)Ru(H)(PhSiCl(OTf)), and ( tBu PONOP)Ru(H)(Ph 2 Si(OTf)). Formic acid dehydrogenation was performed in the presence of triethylamine (TEA), and each species proved competent for gas-pressure generation of CO 2 and H 2 . Finally, the hydride species ( tBu PONOP)Ru(H)Cl, ( tBu PONOP)Ru(H)(OTf), and ( tBu PONOP)Ru(H)(PhSiCl 2 ) exhibited faster catalytic activity than the other compounds tested.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Magnetic, electrical and structural properties of the Re-doped ruthenocuprate Ru{sub 1−x}Re{sub x}Sr{sub 2}GdCu{sub 2}O{sub y}

Highlights: • We investigated the effect of the dilution of magnetic Ru sub-lattice of RuSr{sub 2}GdCu{sub 2}O{sub 8}. • We synthesized the doped compound Rui{sub x}Re{sub x}Sr{sub 2}GdCu{sub 2}O{sub y}, for 3%, 6%, 9% and 12% Re. • Re would affect the electron coupling: just 3 and 6% samples were superconductor. • Superconductivity emergence strongly affects magnetic properties of 3 and 6% samples. • A weak ferromagnetic component is consistent with a globally antiferromagnetic system. - Abstract: Despite the discovery of new superconductors classes, high-Tc oxides continue to be a current topic, because of their complex phase diagrams and doping-dependant effects (allowing one to investigate the interaction between orbitals), as well as structural properties such as lattice distortion and charge ordering, among many others. Ruthenocuprates are magnetic superconductors in which the magnetic transition temperature is much higher than the critical superconducting temperature, making them unique compounds. With the aim of investigating the dilution of the magnetic Ru sub-lattice, we proposed the synthesis of the Ru{sub 1−x}Re{sub x}Sr{sub 2}GdCu{sub 2}O{sub y} ruthenocuprate-type family, adapting the known two-step process (double perovskite + CuO) by directly doping the double perovskite, thus obtaining the perovskite compound Sr{sub 2}GdRu{sub 1−x}Re{sub x}O{sub y}, which represents a new synthesis process to the best of our knowledge. Our samples were structurally characterized through X-ray diffraction, and the patterns were analysed via Rietveld refinement. A complete magnetic characterization as a function of temperature and applied field, as well as transport measurements were carried out. We discuss our results in the light of the two-lattice model for ruthenocuprates, and a relation between RuO{sub 2} (magnetic) and CuO{sub 2} (superconductor) sub-lattices can clearly be observed.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Redox Stability Controls the Cellular Uptake and Activity of Ruthenium-Based Inhibitors of the Mitochondrial Calcium Uniporter (MCU)

The mitochondrial calcium uniporter (MCU) is the ion channel that mediates Ca 2+ uptake in mitochondria. Inhibitors of the MCU are valuable as potential therapeutic agents and tools to study mitochondrial Ca 2+ . The best-known inhibitor of the MCU is the ruthenium compound Ru360. Although this compound is effective in permeabilized cells, it does not work in intact biological systems. We have recently reported the synthesis and characterization of Ru265, a complex that selectively inhibits the MCU in intact cells. In this work, the physical and biological properties of Ru265 and Ru360 are described in detail. Using atomic absorption spectroscopy and X-ray fluorescence imaging, we show that Ru265 is transported by organic cation transporter 3 (OCT3) and taken up more effectively than Ru360. As an explanation for the poor cell uptake of Ru360, we show that Ru360 is deactivated by biological reductants. These data highlight how structural modifications in metal complexes can have profound effects on their biological activities.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Redox Stability Controls the Cellular Uptake and Activity of Ruthenium‐Based Inhibitors of the Mitochondrial Calcium Uniporter (MCU)

Abstract The mitochondrial calcium uniporter (MCU) is the ion channel that mediates Ca 2+ uptake in mitochondria. Inhibitors of the MCU are valuable as potential therapeutic agents and tools to study mitochondrial Ca 2+ . The best‐known inhibitor of the MCU is the ruthenium compound Ru360. Although this compound is effective in permeabilized cells, it does not work in intact biological systems. We have recently reported the synthesis and characterization of Ru265, a complex that selectively inhibits the MCU in intact cells. Here, the physical and biological properties of Ru265 and Ru360 are described in detail. Using atomic absorption spectroscopy and X‐ray fluorescence imaging, we show that Ru265 is transported by organic cation transporter 3 (OCT3) and taken up more effectively than Ru360. As an explanation for the poor cell uptake of Ru360, we show that Ru360 is deactivated by biological reductants. These data highlight how structural modifications in metal complexes can have profound effects on their biological activities.

Woods, Joshua J.↗
DOE OSTI2018

The Effects of Ru and Rh Substitutions on the Magneto-electronic and Optical Properties of the TbNi{sub 5} Intermetallic Compound: An Ab Initio Investigation

In this study, we have performed the first-principles investigation of the structural, electronic, magnetic, and optical properties of TbNi{sub 5}, TbNi{sub 3}Ru{sub 2}, and TbNi{sub 3}Rh{sub 2} compounds. The full-potential linearized augmented plane waves with local orbitals method is used in the framework of density functional theory (DFT) employing the generalized gradient approximation (GGA) for the exchange correlation functional as implemented in WIEN2k package. The structural properties are reposed on the evaluation of the equilibrium lattice parameters of these compounds under hexagonal structure such as lattice constants (a and c), bulk modulus (B), and its first pressure derivative (B{sup ′}). The spin-polarized electronic structures, including band structure and density of states, are calculated employing the GGA plus band correlated Hubbard parameter (GGA + U) scheme. The results show that density of states and magnetic moment of the pure TbNi{sub 5} compound are changed by doping. These changes are observed in the appearance of additional peaks on the spectral density of states (DOS) and in the augmentation of the total magnetic moment of TbNi{sub 3}X{sub 2} (X = Ru and Rh) intermetallic compounds. Based on the electronic structure results, the frequency dependents of optical conductivity are estimated in all the spectra and interpreted in the interband optical absorption part.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Heterobimetallic coordination polymers involving 3d metal complexes and heavier transition metals cyanometallates

The results of the first steps in the design of coordination polymers based on penta- and heptacyanometallates of heavier d transitions metals are presented. The 2D structure of the coordination polymers: [(Mn(acacen)){sub 2}Ru(NO)(CN){sub 5}]{sub n} and two complexes composed of different cyanorhenates, [Ni(cyclam)]{sub 2}[ReO(OH)(CN){sub 4}](ClO{sub 4}){sub 2}(H{sub 2}O){sub 1.25} and [Cu(cyclam)]{sub 2}[Re(CN){sub 7}](H{sub 2}O){sub 12}, was confirmed by single crystal XRD study, the rhenium oxidation state having been proved by the magnetic measurements. An amorphism of [M(cyclam)]{sub 3}[Re(CN){sub 7}]{sub 2} (M=Ni, Cu) polymers does not allow to define strictly their dimensionality and to model anisotropic magnetic behavior of the compounds. However, with high probability a honey-comb like layer structure could be expected for [M(cyclam)]{sub 3}[Re(CN){sub 7}]{sub 2} complexes, studied in this work, because such an arrangement is the most common among the bimetallic assemblies of hexa- and octacyanometallates with a ratio [M(cyclam)]/[M(CN){sub n}]=3/2. For the first time was prepared and fully characterized a precursor (n-Bu{sub 4}N){sub 2}[Ru(NO)(CN){sub 5}], soluble in organic media. - Graphical abstract: The very first results in the design of 2D coordination polymers based on penta- and heptacyanometallates of 4d and5d transitions metals are presented. - Highlights: • Design of coordination polymers based on penta- and heptacyanometallates. • New Ru and Re cyanide based heterobimetallic coordination complexes. • Hydrolysis and ox/red processes involving [Re(CN){sub 7}]{sup 3+} during crystallization. • High magnetic anisotropy of [M(cyclam)]{sub 3}[Re(CN){sub 7}]{sub 2}(H{sub 2}O){sub n}, M=Cu, Ni, complexes.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Spin waves and spin-state transitions in a ruthenate high-temperature antiferromagnet

Ruthenium compounds serve as a platform for fundamental concepts such as spin-triplet superconductivity, Kitaev spin liquids and solid-state analogues of the Higgs mode in particle physics. However, basic questions about the electronic structure of ruthenates remain unanswered, because several key parameters (including Hund’s coupling, spin–orbit coupling and exchange interactions) are comparable in magnitude and their interplay is poorly understood, partly due to difficulties in synthesizing large single crystals for spectroscopic experiments. Here we introduce a resonant inelastic X-ray scattering (RIXS) technique capable of probing collective modes in microcrystals of 4d electron materials. We observe spin waves and spin-state transitions in the honeycomb antiferromagnet SrRu 2 O 6 (ref. 10) and use the extracted exchange interactions and measured magnon gap to explain its high Néel temperature. We expect that the RIXS method presented here will enable momentum-resolved spectroscopy of a large class of 4d transition-metal compounds.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Time-resolved x-ray photoelectron spectroscopy techniques for real-time studies of interfacial charge transfer dynamics

X-ray based spectroscopy techniques are particularly well suited to gain access to local oxidation states and electronic dynamics in complex systems with atomic pinpoint accuracy. Traditionally, these techniques are applied in a quasi-static fashion that usually highlights the steady-state properties of a system rather than the fast dynamics that often define the system function on a molecular level. Novel x-ray spectroscopy techniques enabled by free electron lasers (FELs) and synchrotron based pump-probe schemes provide the opportunity to monitor intramolecular and interfacial charge transfer processes in real-time and with element and chemical specificity. Two complementary time-domain xray photoelectron spectroscopy techniques are presented that are applied at the Linac Coherent Light Source (LCLS) and the Advanced Light Source (ALS) to study charge transfer processes in N3 dye-sensitized ZnO semiconductor nanocrystals, which are at the heart of emerging light-harvesting technologies.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Effect of disorder on the magnetic properties of cubic Mn{sub 2}Ru{sub x}Ga compounds: A first-principles study

We perform first-principles electronic structure calculations to explain the anomalous magnetic behavior of the Mn{sub 2}Ru{sub x}Ga compounds upon Ru doping as shown experimentally recently by Kurt et al. [Phys. Rev. Lett. 112, 027201 (2014)]. Our results suggest that disorder caused by the distribution of the Mn and Ru atoms at various sites reproduces the experimental data. All compounds present antiparallel alignment of the neighboring Mn magnetic moments and, with the exception of Mn{sub 2}RuGa, none of them presents half metallic behavior.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Resistive switching in ultra-thin La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/SrRuO{sub 3} superlattices

Superlattices may play an important role in next generation electronic and spintronic devices if the key-challenge of the reading and writing data can be solved. This challenge emerges from the coupling of low dimensional individual layers with macroscopic world. Here, we report the study of the resistive switching characteristics of a hybrid structure made out of a superlattice with ultrathin layers of two ferromagnetic metallic oxides, La{sub 0.7}Sr{sub 0.3}MnO{sub 3} (LSMO) and SrRuO{sub 3} (SRO). Bipolar resistive switching memory effects are measured on these LSMO/SRO superlattices, and the observed switching is explainable by ohmic and space charge-limited conduction laws. It is evident from the endurance characteristics that the on/off memory window of the cell is greater than 14, which indicates that this cell can reliably distinguish the stored information between high and low resistance states. The findings may pave a way to the construction of devices based on nonvolatile resistive memory effects.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Rethinking 𝛼−RuCl 3 : Parameters, models, and phase diagram

RuCl 3 was likely the first ever deliberately synthesized ruthenium compound, following the discovery of the 44 Ru element in 1844. For a long time it was known as an oxidation catalyst, with its physical properties being discrepant and confusing, until a decade ago when its allotropic form 𝛼−RuCl 3 rose to exceptional prominence. This “rediscovery” of 𝛼−RuCl 3 has not only reshaped the hunt for a material manifestation of the Kitaev spin liquid, but it has opened the floodgates of theoretical and experimental research in the many unusual phases and excitations that the anisotropic-exchange magnets as a class of compounds have to offer. Given its importance for the field of Kitaev materials, it is astonishing that the low-energy spin model that describes this compound and its possible proximity to the much-desired spin-liquid state is still a subject of significant debate ten years later. In the present study, we argue that the existing key phenomenological observations put strong natural constraints on the effective microscopic spin model of 𝛼−RuCl 3 , and specifically on its spin-orbit-induced anisotropic-exchange parameters that are responsible for the nontrivial physical properties of this material. These constraints allow one to focus on the relevant region of the multidimensional phase diagram of the 𝛼−RuCl 3 model, suggest an intuitive description of it via a different parametrization of the exchange matrix, offer a unifying view on the earlier assessments of its parameters, and bring closer together several approaches to the derivation of anisotropic-exchange models. We explore extended phase diagrams relevant to the 𝛼−RuCl 3 parameter space using quasiclassical, Luttinger-Tisza, exact diagonalization, and density-matrix renormalization-group methods, demonstrating a remarkably close quantitative accord between them on the general structure and hierarchy of the phases, with the zigzag, ferromagnetic, and incommensurate phases that are proximate to each other. As a result, one of the highlights is the detailed agreement on the nature of the incommensurate phases that realize two distinct counterrotating helical states.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Response of the Dielectric Parameters of (110)SrTiO{sub 3} Films to the Formation of Ferroelectric Domains in Their Volume

Three-layer SrRuO{sub 3}/SrTiO{sub 3}/SrRuO{sub 3} heterostructures were grown by laser evaporation on (110)LaAlO{sub 3} substrates. Photolithography and ion etching are used to form plane-parallel film capacitors, in which a layer of strontium titanate is placed between two film electrodes of strontium ruthenate. Data on the structure and orientation of the intermediate SrTiO{sub 3} layer in the grown heterostructures were obtained. The variation of the dielectric constant and dielectric loss of the SrTiO{sub 3} intermediate layer upon varying the temperature and intensity of an external electric field was studied.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Origin of metal-insulator transitions in the parent compounds of ruthenium-pnictide superconductors

Here we study the interplay of the structural phase transition, flat electronic band dispersion, and metal-to-insulator transition (MIT) in the parent compounds of the Ru-pnictide superconductors by using first-principles calculations. Our electron and phonon calculations reveal that Ru(P,As) undergo MIT accompanied by orthorhombic to monoclinic distortion at low temperature, but RuSb stays orthorhombic and metallic in agreement with the experimental findings. It is demonstrated that electronic correlation, as treated in DFT + U, DFT + Gutzwiller, and dynamical mean-field theory (DMFT), cannot induce MIT in the undistorted crystal structure. We find that, although small monoclinic distortion can remove the van Hove singularity at the Fermi level, it does not immediately gap out the Fermi surface and a large value of monoclinic distortion is necessary for a clear MIT, suggesting the possibility of an intermediate pseudogapped monoclinic metallic phase. Furthermore, we predict a light-induced two-step insulator-to-metal and structural transitions in the monoclinic phases of RuP and RuAs, which can be tested in future ultrafast pump-probe experiments as an alternative ideal playground to VO 2 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Surfactant-thermal method to synthesize a new Zn(II)-trimesic MOF with confined Ru(bpy){sub 3}{sup 2+} complex

A surfactant-thermal method was used to prepare a new zinc-1,3,5-benzentricarboxylate-based metal-organic framework (ZJU-100) with confined Ru(bpy){sub 3}{sup 2+} (RuBpy) complex by using surfactant PEG 400 as reaction medium. The RuBpy molecules were encapsulated between the 2-D sheets in ZJU-100. ZJU-100 showed bathochromic shift in the steady-state emission spectrum and increased emission lifetimes relative to RuBpy molecules. The extended lifetime is attributed to the reduced nonradiative decay rate due to the stabilization of RuBpy within the rigid MOF framework. These results represent the first example of MOF with confined complex synthesized by surfactant, indicating that the surfactant-thermal method could offer exciting opportunities for preparing new MOFs host/guest materials with novel structures and interesting luminescent properties. - Graphical abstract: A surfactant-thermal method was used to prepare a new zinc-1,3,5-benzentricarboxylate-based metal-organic framework (ZJU-100) with confined Ru(bpy){sub 3}{sup 2+} (RuBpy) complex by using surfactant PEG 400 as reaction medium. - Highlights: • Surfactant-thermal synthesis of crystalline metal-organic framework host/guest materials. • RuBpy molecules were encapsulated between the 2-D sheets of MOFs. • Extended lifetime is observed due to the stabilization of RuBpy within the rigid MOF framework.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗