Heather L. Cuthbert scite author profile

A new quaternary layered transition-metal oxide, Na2Cu2TeO6, has been synthesized under air using stoichiometric (with respect to the cationic elements) mixtures of Na2CO3, CuO, and TeO2. Na2Cu2TeO6 crystallizes in the monoclinic space group C2/m with a = 5.7059(6) A, b = 8.6751(9) A, c = 5.9380(6) A, beta = 113.740(2) degrees, V = 269.05(5) A3, and Z = 2, as determined by single-crystal X-ray diffraction. The structure is composed of infinity(2)[Cu2TeO6] layers with the Na atoms located in the octahedral voids between the layers. Na2Cu2TeO6 is a green nonmetallic compound, in agreement with the electronic structure calculation and electrical resistance measurement. The magnetic susceptibility shows Curie-Weiss behavior between 300 and 600 K with an effective moment of 1.85(2) muB/Cu(II) and theta(c) = -87(6) K. A broad maximum at 160 K is interpreted as arising from short-range one-dimensional antiferromagnetic correlations. With the aid of the technique of magnetic dimers, the short-range order was analyzed in terms of an alternating chain model, with the surprising result that the stronger intrachain coupling involves a super-superexchange pathway with a Cu-Cu separation of >5 A. The J2/J1 ratio within the alternating chain refined to 0.10(1), and the spin gap is estimated to be 127 K.

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Metal-to-Metal Charge Transfer in AWO₄ (A = Mg, Mn, Co, Ni, Cu, or Zn) Compounds with the Wolframite Structure

Dey

et al. 2014

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Using a combination of UV-visible spectroscopy and electronic structure calculations, we have characterized the electronic structures and optical properties of AWO4 (A = Mn, Co, Ni, Cu, Zn, or Mg) tungstates with the wolframite structure. In MgWO4 and ZnWO4, the lowest energy optical excitation is a ligand to metal charge transfer (LMCT) excitation from oxygen 2p nonbonding orbitals to antibonding W 5d orbitals. The energy of the LMCT transition in these two compounds is 3.95 eV for ZnWO4 and 4.06 eV for MgWO4. The charge transfer energies observed for the other compounds are significantly smaller, falling in the visible region of the spectrum and ranging from 2.3 to 3.0 eV. In these compounds, the partially occupied 3d orbitals of the A(2+) ion act as the HOMO, rather than the O 2p orbitals. The lowest energy charge transfer excitation now becomes a metal-to-metal charge transfer (MMCT) excitation, where an electron is transferred from the occupied 3d orbitals of the A(2+) ion to unoccupied antibonding W 5d states. The MMCT value for CuWO4 of 2.31 eV is the lowest in this series due to distortions of the crystal structure driven by the d(9) configuration of the Cu(2+) ion that lower the crystal symmetry to triclinic. The results of this study have important implications for the application of these and related materials as photocatalysts, photoanodes, pigments, and phosphors.

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Electronic structures and low-dimensional magnetic properties of the ordered rocksalt oxidesNa3Cu2SbO6and
Derakhshan
¹
,
Cuthbert
²
,
Greedan
³

et al. 2007
Phys. Rev. B

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Crystal Structure and Physical Properties of a New CuTi₂S₄ Modification in Comparison to the Thiospinel

et al. 2004

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A new modification of CuTi(2)S(4) was prepared from the elements at 425 degrees C. It crystallizes in the rhombohedral space group Rm, with lattice parameters of a = 7.0242(4) A, c = 34.834(4) A, and V = 1488.4(2) A(3) (Z = 12). Two topologically different interlayer regions exist between the close-packed S layers that alternate along the c axis: one comprises both Cu (in tetrahedral voids) and Ti atoms (in octahedral voids), and the second exclusively Ti atoms (again in octahedral voids). In contrast to the known modification, the spinel, Cu-Ti interactions of 2.88 A occur that have bonding character according to the electronic structure calculations. Both CuTi(2)S(4) modifications are metallic Pauli paramagnets due to Ti d contributions. The Pauli susceptibility of the Rm form is larger than that of the thiospinel in quantitative agreement with the LMTO-ASA band structure calculations. The irreversible transformation to the spinel takes place at temperatures above 450 degrees C.

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Synthesis and Structural Characterization of [Cu20Se4(μ3-SePh)12(PPh3)6] and [Ag(SePh)]∞

Cuthbert

Wallbank

Taylor

et al. 2002

Z. anorg. allg. Chem.

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Reaction of lithium phenylselenothiolate, generated in situ from the reductive cleavage of PhSe-SiMe 3 with alkyl lithium reagents and insertion of elemental sulfur, with triphenylphosphine solubilized CuCl affords the molecular cluster complex [Cu 20 Se 4 -(µ 3 -SePh) 12 (PPh 3 ) 6 ] (1). The analogous reaction with AgCl yields the extended structure [Ag(SePh)] ϱ (2) in which an infinite layer of Ag I atoms is capped on either side by µ 4 -SePh ligands. Synthese und strukturelle Charakterisierung von [Cu 20 Se 4 (µ 3 -SePh) 12 (PPh 3 ) 6 ] und [Ag(SePh)] ؕInhaltsübersicht. Die Reaktion von Lithiumphenylselenothiolat, in situ durch reduktive Spaltung von PhSeϪSiMe 3 mit LithiumalkylReagenzien und Insertion elementarem Schwefel gebildet, mit in Triphenylphosphan gelöstem CuCl ergibt den molekularen Clusterkomplex [Cu 20 Se 4 (µ 3 -SePh) 12 (PPh 3 ) 6 ] (1). Die analoge Reaktion mit AgCl ergibt [Ag(SePh)] ϱ (2) mit einer unendlichen Schicht von

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Structure and Properties of Sr_1−xCa_xMn_0.5Ru_0.5O₃ Perovskites: Using Chemical Pressure to Control Mn/Ru Mixed Valency

et al. 2010

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The structure and properties of Sr 1-x Ca x Ru 0.5 Mn 0.5 O 3 compositions have been investigated. Both bond distances and X-ray absorption measurements reveal Mn 3þ þ Ru 5þ T Mn 4þ þ Ru 4þ mixed valency across the entire series. Despite a complete lack of Ru/Mn chemical order, all samples magnetically order between 220 and 300 K. The characteristics and type of magnetic order are sensitive to the occupation and ordering of the Mn e g orbitals, which can be manipulated by changes in chemical pressure, via the Sr/Ca ratio. Sr-rich samples are tetragonally distorted by a cooperative Jahn-Teller distortion (CJTD) that leads to an elongation of the c-axis as well as antiphase rotations of the octahedra about the c-axis (a 0 a 0 ctilt system). The CJTD results from orbital ordering involving occupied d z 2 orbitals on Mn 3þ , which stabilize C-type antiferromagnetic order. For Sr-rich samples, the various oxidation states contribute in approximately equal proportions (i.e., Ru þ4.5 and Mn þ3.5 ). Substituting Ca 2þ for Sr 2þ triggers additional rotations of the octahedra (ab þ atilt system) that result in orthorhombic symmetry for Sr 1-x Ca x Mn 0.5 Ru 0.5 O 3 samples with x g 0.3. The crossover to orthorhombic symmetry is accompanied by the loss of orbital order and the emergence of an itinerant electron ferrimagnetic state. X-ray absorption near edge structure (XANES) measurements show that as the Ca 2þ content increases there is a shift in the valence degeneracy toward Mn 4þ þ Ru 4þ . This helps to explain the absence of orbital ordering in Ca-rich samples, as well as the crossover from antiferromagnetism to ferrimagnetism. Neutron diffraction and ac susceptibility measurements show that CaRu 0.5 Mn 0.5 O 3 undergoes magnetic phase separation into a disordered ferrimagnetic state (T C ≈ 230 K) and a G-type antiferromagnetic state (T N ≈ 95 K).

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Alk‐2‐ynyl Trimethylsilyl Chalcogenoethers by Nucleophilic Substitution of Propargyl Bromides

et al. 2006

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Synthesis, Structure, and Unexpected Magnetic Properties of La₃Re₂O₁₀

et al. 2007

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Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n'arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. Questions? Contact the NRC Publications Archive team atPublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information. NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. For the publisher's version, please access the DOI link below./ Pour consulter la version de l'éditeur, utilisez le lien DOI ci-dessous.http://doi.org/10.1021/ic701011rAccess and use of this website and the material on it are subject to the Terms and Conditions set forth at Synthesis, structure, and unexpected magnetic properties of La₃Re₂O₁₀ Cuthbert, Heather L.; Greedan, John E.; Vargas-Baca, Ignacio; Derakhshan, Shahab; Swainson, Ian P.http://nparc.cisti-icist.nrc-cnrc.gc.ca/fra/droits L'accès à ce site Web et l'utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D'UTILISER CE SITE WEB. NRC Publications Record / Notice d'Archives des publications de CNRC:http://nparc.cisti-icist.nrc-cnrc.gc.ca/eng/view/object/?id=7578386d-bb5d-4976-bcf7-9ff75d47288c http://nparc.cisti-icist.nrc-cnrc.gc.ca/fra/voir/objet/?id=7578386d-bb5d-4976-bcf7-9ff75d47288c dimer units of two edge-shared ReO 6 octahedra, separated by La 3+ within the lattice. The Re−Re distance within the dimer units is 2.488 Å, which is indicative of metal−metal bonding with a bond order of 1.5. The average oxidation state of the Re atom is +5.5, leaving one unpaired electron per dimer unit (S ) 1/2). Although the closest interdimer distance is 5.561 Å, the magnetic susceptibility data and heat capacity measurements indicate this compound exhibits both short-and long-range magnetic order at surprisingly high temperatures. The zero field cooled (ZFC) magnetic susceptibility data show two broad features at 55 and 105 K, indicating short-range order, and a sharper cusp at 18 K, which signifies long-range antiferromagnetic order. The heat capacity of La 3 Re 2 O 10 shows a λ-type anomaly at 18 K, which is characteristic of long-range magnetic order. DFT calculations determined that the unpaired electron resides in a π-bonding orbital and that the unpaired electron density is widely delocalized over the atoms within the dimer, with high values at the bridging oxygens. Extended Hückel spin dimer calculations suggest possible interaction pathways between these dimer units within the crystal lattice. Results from ...

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