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    A study of di(amino)stibines with terminal Sb( iii ) hydrogen-ligands by X-ray- and neutron-diffraction
    (Royal Society of Chemistry, 2019-01-31) Schwamm, RJ; Edwards, AJ; Fitchett, CM; Coles, MP
    The bis(amidodimethyl)disiloxane ligands [O{SiMe2NR}2]2− (R = 2,6-Me2C6H3 (Ar′) and 2,6-iPr2C6H3 (Ar), abbreviated [NONR]2−, are a stable support for Sb(III) complexes of general formula Sb(NONR)X (X = Cl, H). The compounds are monomeric in the solid-state, with bidentate N,N′-coordination of the [NONR]2− and terminal chloride/hydrogen-ligands. Sb(NONAr′)H was analyzed by single-crystal neutron diffraction, giving the first accurate parameters for the Sb–H bond to an antimony(III) centre. © Royal Society of Chemistry 2025.
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    First Holocene cryptotephras in mainland Australia reported from sediments at Lake Keilambete, Victoria, Australia
    (Elsevier, 2017-05) Smith, RE; Tyler, JJ; Reeves, JM; Blockley, S; Jacobsen, GE
    We report the first observations of Holocene cryptotephra deposits in lacustrine sediments from mainland Australia. All counts of cryptotephra shards are presented, but we focus on two prominent peaks of dark coloured glass shards representing distinct cryptotephras within the sediments of Lake Keilambete, Victoria, southeast Australia. These two basaltic cryptotephras, aged 4589-3826 cal BP and 7149-5897 cal BP, may have derived from eruptions of Mts Gambier or Schank, South Australia. In addition, colourless shards, most likely of silicic composition and therefore unlikely to emanate from an Australian volcano were observed, suggesting a distant volcanic source beyond Australia. The presence of both the ‘local’ basaltic shards and the distal silicic shards highlights the potential to identify isochronous marker horizons in southern Australian sediments, thus potentially enabling a long-term goal of establishing a novel chronostratigraphic tool based on a cryptotephra network. © 2016 Elsevier B.V.
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    Designing novel tunable Mn-based inorganic oxyfluoride pigments
    (Elsevier, 2024-06) Lehr, B; Zurowski, G; Chhoeun, J; Kumar, K; Nolis, G; Shanahan, J; Kilpatrick, K; Rojas, K; Cabana, J; Kissel, D; Avdeev, M; Sullivan, E
    A high tunability of green-blue colors in the manganese-doped oxyfluoride Sr2.5A0.5Mn0.1MO4F (A = Ca, Sr, Ba; M = Al, Ga) and anion-deficient Sr2.5A0.5Mn0.1MO4-αF1-δ (A = Ca, Sr, Ba; M = Al, Ga) is reported, and the chromophores responsible for this intense pigmentation are investigated. The hues exhibited by these materials are quantified via diffuse reflectance UV/Vis spectroscopy and measurement of their direct band gaps via Tauc plot. It is shown that choice of A cation (A = Ca, Sr, Ba) and M cation (M = Al, Ga) for as-synthesized phases Sr2.5A0.5Mn0.1MO4F yield a wide range of green colors (band gap range 2.70–2.96 eV). Treatment of these phases under reducing conditions according to Sr2.5A0.5Mn0.1MO4-αF1-δ (A = Ca, Sr, Ba; M = Al, Ga) induces anion non-stoichiometry, shifting the observed colors to a wide range of blue/blue-purple hues (band gaps from 3.31 to 3.66 eV), showing potential as tunable inorganic blue pigments. Density field theory (DFT) calculations support the preferential occupation of the smaller 8-coordinate Sr(2) site by the substituted Mn2+ cation. X-ray absorption near-edge structure (XANES) data reveal more subtle nuances in the interplay between formal manganese oxidation state, crystallographic site and observed hue. In general, for as synthesized (green) Sr2.5A0.5Mn0.1MO4F (A = Ca, Sr, Ba; M = Al, Ga), the edge position in Mn K-edge XANES is consistent with mixed Mn3+-Mn4+ oxidation state whilst a clear pre-edge structure suggesting that Mn is present on a tetrahedral site. This would suggest that during the reduction step, Mn3+/Mn4+ is reduced to entirely Mn2+ and migrates from the tetrahedral to the Sr(2) lattice site. © 2024 Elsevier Ltd. All rights reserved.
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    Higher order exchange driven noncoplanar magnetic state and large anomalous hall effects in electron doped kagome magnet Mn3Sn
    (Springer Nature, 2024-05-22) Singh, C; Jamaluddin, S; Pradhan, S; Nandy, AK; Tokunaga, M; Avdeev, M; Nayak, AK
    Owing to geometrical frustration in the kagome lattice, Mn3Sn displays a 120° in-plane triangular antiferromagnetic order, a manifestation of exchange interaction within the Heisenberg model. Here, we show the formation of a tunable noncoplanar magnetic ground state stabilized by higher-order exchange interactions in electron-doped Mn3Sn samples. Our density Functional Theory calculations reveal that the higher-order exchange induces a partial out-of-plane alignment of the Mn moments, resulting in a canted magnetic state, further experimentally confirmed by neutron diffraction study along with 60 T magnetic and Hall resistivity measurements. Interestingly, we find a large scalar spin chirality-induced Hall signal depending on the degree of non-coplanarity of the Mn moments. Additionally, we demonstrate simultaneous manipulation of two-component order-parameter in the system, where the two Hall signals can be independently manipulated. The present study explores the quantum phenomena associated with the coexistence of multiple magnetic orders and their prospective use in spintronic devices. © 2024 Springer Nature Limited.
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    Molecular thorium trihydrido clusters stabilized by cyclopentadienyl ligands
    (Wiley, 2020-07-06) Chen, R; Qin, G; Li, S; Edwards, AJ; Piltz, RO; Del Rosal, I; Maron, L; Cui, D; Cheng, J
    Hydrogenolysis of alkyl‐substituted cyclopentadienyl (CpR) ligated thorium tribenzyl complexes [(CpR)Th(p‐CH2‐C6H4‐Me)3] (1–6) afforded the first examples of molecular thorium trihydrido complexes [(CpR)Th(μ‐H)3]n (CpR=C5H2(tBu)3 or C5H2(SiMe3)3, n=5; C5Me4SiMe3, n=6; C5Me5, n=7; C5Me4H, n=8; 7–10 and 12) and [(Cp#)12Th13H40] (Cp#=C5H4SiMe3; 13). The nuclearity of the metal hydride clusters depends on the steric profile of the cyclopentadienyl ligands. The hydrogenolysis intermediate, tetra‐nuclear octahydrido thorium dibenzylidene complex [(Cpttt)Th(μ‐H)2]4(μ‐p‐CH‐C6H4‐Me)2 (Cpttt=C5H2(tBu)3) (11) was also isolated. All of the complexes were characterized by NMR spectroscopy and single‐crystal X‐ray analysis. Hydride positions in [(CpMe4)Th(μ‐H)3]8 (CpMe4=C5Me4H) were further precisely confirmed by single‐crystal neutron diffraction. DFT calculations strengthen the experimental assignment of the hydride positions in the complexes 7 to 12. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim