| 1. |
- Ivanov, Alexander, et al.
(författare)
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A fixation mode of gold from solutions using heterogeneous reaction of cadmium dicyclohexyl dithiophosphate with H[AuCl4]. Structural and (13C, 31P) CP/MAS NMR studies and thermal behaviour of crystalline polymeric gold(I) dicyclohexyl dithiophosphate and bis(dicyclohexylthiophosphoryl) disulphide
- 2013
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Ingår i: Journal of Molecular Structure. - : Elsevier BV. - 0022-2860 .- 1872-8014. ; 1034, s. 152-161
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Tidskriftsartikel (refereegranskat)abstract
- Two novel compounds: polynuclear catena-poly[bis(3-O,O’-di-cyclo-hexyldithiophosphato-S,S,S’)digold(I)] (Au–Au) (1) and crystalline bis(O,O’-di-cyclo-hexylthiophosphoryl)disulphide, (cyclo-C6H11O)2P(S)S–S(S)P(O-cyclo-C6H11) (2) were prepared using heterogeneous reaction between freshly precipitated binuclear cadmium(II) dithiophosphate (Dtph), [Cd2{S2P(O-cyclo-C6H11}4] and H[AuCl4] in 2 M hydrochloric acid. The isolated compounds 1 and 2 (the fixation mode of gold from the solution and the oxidised form of Dtph groups, respectively) have been studied by means of single-crystal X-ray diffraction, 13C and 31P cross-polarisation / magic-angle-spinning (CP/MAS) NMR spectroscopy and simultaneous thermal analysis (STA). Centrosymmetric binuclear molecule of 1, [Au2{S2P(O-cyclo-C6H11)2}2] comprises a pair of -bridging di-cyclo-hexyl Dtph ligands, linking two neighbouring gold atoms, and displays additional intramolecular aurophilic bond Au···Au. At the supramolecular level of structural self-organisation of complex 1, infinite polymeric zigzag chains arise due to pairs of the secondary bonds Au···S between neighbouring binuclear molecules. Centrosymmetric molecule of 2 displays two O,O-di-cyclo-hexythiophosphoryl fragments, which are connected by the chemical bond S(1)–S(1)a, and a planar zigzag array [S=P–S–S–P=S] passing through the central part of the molecule. To characterise additionally the Dtph groups in both compounds 1 and 2, chemical shift anisotropy (CSA) parameters (aniso and) were calculated from spinning sideband manifolds in experimental 31P MAS NMR spectra. The thermal behaviour of complex 1 was studied using simultaneous thermal analysis (a combination of TG and DSC) under an argon atmosphere. The thermal behaviour displays stepwise mass loss, comprising thermal decompositions of the organic and inorganic parts of 1 with gold(I) dithio-meta-phosphate and reduced metallic gold as the intermediate and the final products, respectively.
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| 2. |
- Rodina, Tatyana A., et al.
(författare)
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Crystalline O,O’-di-sec-butyl and O,O’-diethyl dithiophosphate platinum(II) complexes : Synthesis, 13C and 31P CP/MAS NMR, single crystal X-ray diffraction studies and thermal behaviour
- 2011
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Ingår i: Polyhedron. - : Elsevier BV. - 0277-5387 .- 1873-3719. ; 30:13, s. 2210-2217
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Tidskriftsartikel (refereegranskat)abstract
- Crystalline bis(O,O’-di-sec-butyldithiophosphato)platinum(II) was prepared and studied by means of 31P, 13C CP/MAS NMR spectroscopy and single-crystal X-ray diffraction. The unit cell of the platinum(II) compound is comprised of one centrosymmetric mononuclear molecule [Pt{S2P(O-sec-C4H9)2}2], in which the dithiophosphate groups display structural equivalence in both 31P NMR and XRD data. A pair of the dithiophosphate ligands exhibit the same S,S’-bidentate chelating structural function and form two planar four-membered chelate rings, [PtS2P], in this molecule. The planar configuration of the [PtS4] chromophore in structure 1 is governed by the dsp2-hybrid state of platinum(II). The structural states of the dithiophosphate groups in two different samples of complex 1 (one crystallised from ethanol and the other one precipitated from an aqueous solution) are all characterised by almost rhombic 31P chemical shift tensors. The observed essential dispersion of the 31P NMR chemical shift is caused by a coexistence of six optical isomers of molecule 1. The thermal behaviour of this compound was studied by means of simultaneous thermal analysis (a combination of TG and DSC) under an argon atmosphere. The thermal behaviour shows that the mass of 1 is lost in three steps, involving successive thermal decompositions of the organic and inorganic parts of this compound with platinum(II) dithio-meta-phosphate and reduced metallic platinum as the intermediate and the final products, respectively.
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| 3. |
- Rodina, Tatyana A., et al.
(författare)
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Fixation modes of gold(III) from solutions using cadmium(II) dithiocarbamates : Preparation, supramolecular structure and thermal behaviour of polynuclear and heteropolynuclear gold(III) complexes: bis(N,N-dialkyldithiocarbamato-S,S’)gold(III) polychlorometallates, [Au(S2CNR2)2]nX (n =1: X = [AuCl4]–; n = 2: X = [CdCl4]2–, [Cd2Cl6]2–)
- 2012
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Ingår i: Polyhedron. - : Elsevier BV. - 0277-5387 .- 1873-3719. ; 40:1, s. 53-64
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Tidskriftsartikel (refereegranskat)abstract
- Four novel heteropolynuclear and polynuclear complexes of the general formulae [Au(S2CNR2)2]2X (X = [CdCl4]2-, R = CH3 (1); X = [Cd2Cl6]2-, R = C3H7 (2)) and [Au(S2CNR2)2][AuCl4] (R = iso-C3H7 (3); R = iso-C4H9 (4)) were prepared using heterogeneous reactions between appropriate freshly precipitated binuclear cadmium(II) dialkyl dithiocarbamates and AuCl3 in 2 M hydrochloric acid. The isolated complexes were studied by 13C CP/MAS NMR spectroscopy, single-crystal X-ray diffraction and simultaneous thermal analysis (STA) under an argon atmosphere. In all molecular structures (1–4), one of the gold atoms coordinates two dialkyl dithiocarbamate ligands in the S,S’-bidentate mode, forming a square-planar coordination polygon [AuS4], while the other gold atom (in 3 and 4) has four neighbouring chlorine atoms [AuCl4]. At the supramolecular level, compounds 1 and 2 comprise binuclear cations, [Au2{S2CN(CH3)2}4]2+ and polynuclear chains, ([Au{S2CN(C3H7)2}2]+)n in a combination with [CdCl4]2- and [Cd2Cl6]2- anions, respectively. Unexpected structural distinctions at the supramolecular level were discovered for the chemically related compounds 3 and 4. In these ionic complexes, there are either cationic trinuclear formations, {[Au{S2CN(iso-C3H7)2}2]2[AuCl4]}+, or polynuclear chains, ([Au{S2CN(iso-C4H9)2}2]+)n, both combined with [AuCl4]– anions, in the structural basis of compounds 3 and 4, respectively.
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| 4. |
- Semiletov, Igor, et al.
(författare)
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Acidification of East Siberian Arctic Shelf waters through addition of freshwater and terrestrial carbon
- 2016
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Ingår i: Nature Geoscience. - : Springer Science and Business Media LLC. - 1752-0894 .- 1752-0908. ; 9, s. 361-365
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Tidskriftsartikel (refereegranskat)abstract
- Ocean acidification affects marine ecosystems and carbon cycling, and is considered a direct effect of anthropogenic carbon dioxide uptake from the atmosphere. Accumulation of atmospheric CO2 in ocean surface waters is predicted to make the ocean twice as acidic by the end of this century. The Arctic Ocean is particularly sensitive to ocean acidification because more CO2 can dissolve in cold water. Here we present observations of the chemical and physical characteristics of East Siberian Arctic Shelf waters from 1999, 2000–2005, 2008 and 2011, and find extreme aragonite undersaturation that reflects acidity levels in excess of those projected in this region for 2100. Dissolved inorganic carbon isotopic data and Markov chain Monte Carlo simulations of water sources using salinity and delO-18 data suggest that the persistent acidification is driven by the degradation of terrestrial organic matter and discharge of Arctic river water with elevated CO2 concentrations, rather than by uptake of atmospheric CO2. We suggest that East Siberian Arctic Shelf waters may become more acidic if thawing permafrost leads to enhanced terrestrial organic carbon inputs and if freshwater additions continue to increase, which may affect their efficiency as a source of CO2.
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| 5. |
- Shakhova, Natalia, et al.
(författare)
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Current rates and mechanisms of subsea permafrost degradation in the East Siberian Arctic Shelf
- 2017
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- The rates of subsea permafrost degradation and occurrence of gas-migration pathways are key factors controlling the East Siberian Arctic Shelf (ESAS) methane (CH4) emissions, yet these factors still require assessment. It is thought that after inundation, permafrost-degradation rates would decrease over time and submerged thaw-lake taliks would freeze; therefore, no CH4 release would occur for millennia. Here we present results of the first comprehensive scientific re-drilling to show that subsea permafrost in the near-shore zone of the ESAS has a downward movement of the ice-bonded permafrost table of similar to 14 cm year(-1) over the past 31-32 years. Our data reveal polygonal thermokarst patterns on the seafloor and gas-migration associated with submerged taliks, ice scouring and pockmarks. Knowing the rate and mechanisms of subsea permafrost degradation is a prerequisite to meaningful predictions of near-future CH4 release in the Arctic.
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| 6. |
- Shakhova, Natalia, et al.
(författare)
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Ebullition and storm-induced methane release from the East Siberian Arctic Shelf
- 2014
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Ingår i: Nature Geoscience. - 1752-0894 .- 1752-0908. ; 7:1, s. 64-70
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Tidskriftsartikel (refereegranskat)abstract
- Vast quantities of carbon are stored in shallow Arctic reservoirs, such as submarine and terrestrial permafrost. Submarine permafrost on the East Siberian Arctic Shelf started warming in the early Holocene, several thousand years ago. However, the present state of the permafrost in this region is uncertain. Here, we present data on the temperature of submarine permafrost on the East Siberian Arctic Shelf using measurements collected from a sediment core, together with sonar-derived observations of bubble flux and measurements of seawater methane levels taken from the same region. The temperature of the sediment core ranged from -1.8 to 0 degrees C. Although the surface layer exhibited the lowest temperatures, it was entirely unfrozen, owing to significant concentrations of salt. On the basis of the sonar data, we estimate that bubbles escaping the partially thawed permafrost inject 100-630 mg methane m(-2) d(-1) into the overlying water column. We further show that water-column methane levels had dropped significantly following the passage of two storms. We suggest that significant quantities of methane are escaping the East Siberian Shelf as a result of the degradation of submarine permafrost over thousands of years. We suggest that bubbles and storms facilitate the flux of this methane to the overlying ocean and atmosphere, respectively.
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| 7. |
- Shakhova, Natalia, et al.
(författare)
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The East Siberian Arctic Shelf : towards further assessment of permafrost-related methane fluxes and role of sea ice
- 2015
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Ingår i: Philosophical Transactions. Series A. - : The Royal Society. - 1364-503X .- 1471-2962. ; 373:2052
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Tidskriftsartikel (refereegranskat)abstract
- Sustained release of methane (CH4) to the atmosphere from thawing Arctic permafrost may be a positive and significant feedback to climate warming. Atmospheric venting of CH4 from the East Siberian Arctic Shelf (ESAS) was recently reported to be on par with flux from the Arctic tundra; however, the future scale of these releases remains unclear. Here, based on results of our latest observations, we show that CH4 emissions from this shelf are likely to be determined by the state of subsea permafrost degradation. We observed CH4 emissions from two previously understudied areas of the ESAS: the outer shelf, where subsea permafrost is predicted to be discontinuous or mostly degraded due to long submergence by seawater, and the near shore area, where deep/open taliks presumably form due to combined heating effects of seawater, river run-off, geothermal flux and pre-existing thermokarst. CH4 emissions from these areas emerge from largely thawed sediments via strong flare-like ebullition, producing fluxes that are orders of magnitude greater than fluxes observed in background areas underlain by largely frozen sediments. We suggest that progression of subsea permafrost thawing and decrease in ice extent could result in a significant increase in CH4 emissions from the ESAS.
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