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Vogt LI, Cotelesage JJH, Dolgova NV, Boyes C, Qureshi M, Sokaras D, Sharifi S, George SJ, Pickering IJ, George GN. Sulfur X-ray Absorption and Emission Spectroscopy of Organic Sulfones. J Phys Chem A 2023; 127:3692-3704. [PMID: 36912654 DOI: 10.1021/acs.jpca.2c08647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/14/2023]
Abstract
The sulfones are a widespread group of organo-sulfur compounds, which contain the sulfonyl SO2 group attached to two carbons and have a formal sulfur oxidation state of +2. We have examined the sulfur K near-edge X-ray absorption spectroscopy (XAS) of a range of different sulfones and find substantial spectroscopic variability depending upon the nature of the coordination to the sulfonyl group. We have also examined the sulfur Kβ X-ray emission spectroscopy (XES) of selected representative sulfones. Density functional theory simulations show satisfactory reproduction of both absorption and emission spectra while enabling assignment of the various transitions comprising the spectra. The correspondence between observed and simulated spectra shows promise for ab initio prediction of sulfur X-ray absorption and emission spectra of sulfones of any substituent. The absorption spectra and, to a lesser extent, the emission spectra are sensitive to the nature of the organic groups bound to the sulfonyl (SO2) moiety, clearly showing the potential of X-ray spectroscopy as an in situ probe of sulfone chemistry.
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Affiliation(s)
- Linda I Vogt
- Molecular and Environmental Sciences Group, Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada
| | - Julien J H Cotelesage
- Molecular and Environmental Sciences Group, Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada
| | - Natalia V Dolgova
- Molecular and Environmental Sciences Group, Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada
| | - Curtis Boyes
- Molecular and Environmental Sciences Group, Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada
| | - Muhammad Qureshi
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Dimosthenis Sokaras
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Samin Sharifi
- Chevron Energy Technology Company, Richmond, California 94802, United States
| | - Simon J George
- Simon Scientific, P.O. Box 71024, Richmond, California 94807, United States
| | - Ingrid J Pickering
- Molecular and Environmental Sciences Group, Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada.,Department of Chemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5C9, Canada
| | - Graham N George
- Molecular and Environmental Sciences Group, Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada.,Department of Chemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5C9, Canada
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Frank P, Benfatto M. Symmetry Breaking in Solution-Phase [Cu(tsc) 2(H 2O) 2] 2+: Emergent Asymmetry in Cu-S Distances and in Covalence. J Phys Chem B 2021; 125:10779-10795. [PMID: 34546762 DOI: 10.1021/acs.jpcb.1c05022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The structure of aqueous Cu(II)-bis-thiosemicarbazide, [Cu(tsc)2]2+, is reported following EXAFS and MXAN analyses of the copper K-edge X-ray absorption (XAS) spectrum. The rising K-edge feature at 8987.1 eV is higher energy than those of crystalline models, implying unique electronic and structural solution states. EXAFS analysis (k = 2-13 Å-1; 2 × Cu-N = 2.02 ± 0.01 Å; 2 × Cu-S = 2.27 ± 0.01 Å; Cu-Oax = 2.41 ± 0.04 Å) could not resolve 5- versus 6-coordinate models. However, MXAN fits converged to an asymmetric broken symmetry 6-coordinate model with cis-disposed TSC ligands (Cu-Oax = 2.07 and 2.54 Å; Cu-N = 1.94 Å, 1.98 Å; Cu-S = 2.20 Å, 2.41 Å). Transition dipole integral evaluation of the sulfur K-edge XAS 1s → 3p valence transition feature at 2470.7 eV yielded a Cu-S covalence of 0.66 e-, indicating Cu1.34+. The high Cu-S covalence and short Cu-S bond in aqueous [Cu(tsc)2(H2O)2]2+ again contradict the need for a protein rack to explain the unique structure of the blue copper active site. MXAN models of dissolved Cu(II) complex ions have invariably featured broken centrosymmetry. The potential energy ground state for dissolved Cu(II) evidently includes the extended solvation field, providing a target for improved physical theory. A revised solvation model for aqueous Cu(II), |[Cu(H2O)5]·14H2O|2+, is presented.
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Affiliation(s)
- Patrick Frank
- Stanford Synchrotron Radiation Lightsource, SLAC, Stanford University, Menlo Park, California 94025, United States.,Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Maurizio Benfatto
- Laboratori Nazionali di Frascati-INFN, P.O. Box 13, 00044 Frascati, Italy
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Qureshi M, Nowak SH, Vogt LI, Cotelesage JJH, Dolgova NV, Sharifi S, Kroll T, Nordlund D, Alonso-Mori R, Weng TC, Pickering IJ, George GN, Sokaras D. Sulfur Kβ X-ray emission spectroscopy: comparison with sulfur K-edge X-ray absorption spectroscopy for speciation of organosulfur compounds. Phys Chem Chem Phys 2020; 23:4500-4508. [PMID: 33355326 DOI: 10.1039/d0cp05323f] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Until recently, sulfur was known as a "spectroscopically silent" element because of a paucity of convenient spectroscopic probes suitable for in situ chemical speciation. In recent years the technique of sulfur K-edge X-ray absorption spectroscopy (XAS) has been used extensively in sulfur speciation in a variety of different fields. With an initial focus on reduced forms of organic sulfur, we have explored a complementary X-ray based spectroscopy - sulfur Kβ X-ray emission spectroscopy (XES) - as a potential analytical tool for sulfur speciation in complex samples. We compare and contrast the sensitivity of sulfur Kβ XES with that of sulfur K-edge XAS, and find differing sensitivities for the two techniques. In some cases an approach involving both sulfur K-edge XAS and sulfur Kβ XES may be a powerful combination for deducing sulfur speciation in samples containing complex mixtures.
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Affiliation(s)
- Muhammad Qureshi
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, USA.
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Frank P, Carlson RMK, Carlson EJ, Hedman B, Hodgson KO. Biological sulfur in the blood cells of Ascidia ceratodes: XAS spectroscopy and a cellular-enzymatic hypothesis for vanadium reduction in the ascidians. J Inorg Biochem 2020; 205:110991. [PMID: 31945647 PMCID: PMC7033024 DOI: 10.1016/j.jinorgbio.2019.110991] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Revised: 12/12/2019] [Accepted: 12/31/2019] [Indexed: 10/25/2022]
Abstract
Two samples of living blood cells and of cleared blood plasma from the Phlebobranch tunicate Ascidia ceratodes from Bodega Bay, California, and one of fresh Henze solution from A. ceratodes of Monterey Bay, California, have been examined using sulfur K-edge x-ray absorption spectroscopy (XAS). Biological sulfur included sulfate esters, sulfate and bisulfate ions, benzothiazole, thianthrene, epi-sulfide, thiol and disulfide. Glutathione dominated reduced sulfur, from which an average intracellular Voltage of -0.21 V was calculated. Sulfate-bisulfate ratios yielded blood cell pH values of 2.0 and 2.8. Total blood cell [sulfur] was 373±9 mM or 296±73 mM from BaSO4 gravimetry. Two plasma samples (pH 6.9 or 7.0; [S] = 33±6 mM or 26±4 mM) were dominated by sulfate and disulfide. Fresh Henze solution evidenced a sulfur inventory similar to blood cells, with calculated pH = 2.7. A V(III)-sulfonate fraction varied systematically with intracellular pH across six independent blood cell samples, implying a vanadium mobilization pathway. Bodega Bay and Monterey Bay A. ceratodes appear to maintain alternative suites of low-valent sulfur. The significance of the vanabins to vanadium metabolism is critically examined in terms of known protein - V(IV) biochemistry. Finally, a detailed hypothesis for the reduction of [VO4]3- to V(III) in ascidians is introduced. A vanadium oxido-reductase is proposed to span the signet ring membrane and to release V(III) into the inner acidic vacuole. The V(V) to V(III) reduction is predicted require an inner-sphere mechanism, a thiol reductant, 7-coordinate V(III), a biologically accessible Voltage, and proton-facilitated release of V(III).
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Affiliation(s)
- Patrick Frank
- Stanford Synchrotron Radiation laboratory, SLAC, Stanford University, Menlo Park, CA 94025, United States of America; Department of Chemistry, Stanford University, Stanford, CA 94305, United States of America.
| | - Robert M K Carlson
- Institute for Materials and Energy Sciences, SLAC, Stanford University, Menlo Park, CA 94025, United States of America
| | - Elaine J Carlson
- University of California, San Francisco, CA 94143, United States of America
| | - Britt Hedman
- Stanford Synchrotron Radiation laboratory, SLAC, Stanford University, Menlo Park, CA 94025, United States of America
| | - Keith O Hodgson
- Stanford Synchrotron Radiation laboratory, SLAC, Stanford University, Menlo Park, CA 94025, United States of America; Department of Chemistry, Stanford University, Stanford, CA 94305, United States of America
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Vogt LI, Cotelesage JJH, Dolgova NV, Titus CJ, Sharifi S, George SJ, Pickering IJ, George GN. X-ray absorption spectroscopy of organic sulfoxides. RSC Adv 2020; 10:26229-26238. [PMID: 35519739 PMCID: PMC9055334 DOI: 10.1039/d0ra04653a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 07/02/2020] [Indexed: 01/21/2023] Open
Abstract
Organic sulfoxides, a group of compounds containing the sulfinyl S
Created by potrace 1.16, written by Peter Selinger 2001-2019
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O group, are widespread in nature, important in health and disease, and used in a variety of applications in the pharmaceutical industry. We have examined the sulfur K-edge X-ray absorption near-edge spectra of a range of different sulfoxides and find that their spectra are remarkably similar. Spectra show an intense absorption peak that is comprised of two transitions; a S 1s → (S–O)σ* and a S 1s → [(S–O)π* + (S–C)σ*] transition. In most cases these are sufficiently close in energy that they are not properly resolved; however for dimethylsulfoxide the separation between these transitions increases in aqueous solution due to hydrogen bonding to the sulfinyl oxygen. We also examined tetrahydrothiophene sulfoxide using both the sulfur and oxygen K-edge. This compound has a mild degree of ring strain at the sulfur atom, which changes the energies of the two transitions so that the S 1s → [(S–O)π* + (S–C)σ*] is below the S 1s → (S–O)σ*. A comparison of the oxygen K-edge X-ray absorption near-edge spectra of tetrahydrothiophene sulfoxide with that of an unhindered sulfoxide shows little change, indicating that the electronic environment of oxygen is very similar. This study develops an understanding of the X-ray absorption near-edge spectra of organic sulfoxides using the sulfur and oxygen K-edges.![]()
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Affiliation(s)
- Linda I. Vogt
- Molecular and Environmental Sciences Group
- Department of Geological Sciences
- University of Saskatchewan
- Saskatoon
- Canada
| | - Julien J. H. Cotelesage
- Molecular and Environmental Sciences Group
- Department of Geological Sciences
- University of Saskatchewan
- Saskatoon
- Canada
| | - Natalia V. Dolgova
- Molecular and Environmental Sciences Group
- Department of Geological Sciences
- University of Saskatchewan
- Saskatoon
- Canada
| | | | | | | | - Ingrid J. Pickering
- Molecular and Environmental Sciences Group
- Department of Geological Sciences
- University of Saskatchewan
- Saskatoon
- Canada
| | - Graham N. George
- Molecular and Environmental Sciences Group
- Department of Geological Sciences
- University of Saskatchewan
- Saskatoon
- Canada
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George GN, Pickering IJ, Cotelesage JJH, Vogt LI, Dolgova NV, Regnier N, Sokaras D, Kroll T, Sneeden EY, Hackett MJ, Goto K, Block E. Visualizing sulfur with X-rays: From molecules to tissues. PHOSPHORUS SULFUR 2019. [DOI: 10.1080/10426507.2019.1602618] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Graham N. George
- Department of Geological Sciences, University of Saskatchewan, Saskatoon, Canada
- Department of Chemistry, University of Saskatchewan, Saskatoon, Canada
| | - Ingrid J. Pickering
- Department of Geological Sciences, University of Saskatchewan, Saskatoon, Canada
- Department of Chemistry, University of Saskatchewan, Saskatoon, Canada
| | | | - Linda I. Vogt
- Department of Geological Sciences, University of Saskatchewan, Saskatoon, Canada
| | - Natalia V. Dolgova
- Department of Geological Sciences, University of Saskatchewan, Saskatoon, Canada
| | - Nathan Regnier
- Department of Chemistry, University of Saskatchewan, Saskatoon, Canada
| | | | - Thomas Kroll
- Stanford Synchrotron Radiation Lightsource, Menlo Park, California, USA
| | - Eileen Y. Sneeden
- Stanford Synchrotron Radiation Lightsource, Menlo Park, California, USA
| | - Mark J. Hackett
- Department of Geological Sciences, University of Saskatchewan, Saskatoon, Canada
| | - Kei Goto
- Department of Chemistry, Tokyo Institute of Technology, Tokyo, Japan
| | - Eric Block
- Department of Chemistry, University at Albany – State University of New York, Albany, New York, USA
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Frank P, Sarangi R, Hedman B, Hodgson KO. Synchrotron X-radiolysis of l-cysteine at the sulfur K-edge: Sulfurous products, experimental surprises, and dioxygen as an oxidoreductant. J Chem Phys 2019; 150:105101. [PMID: 30876351 PMCID: PMC7791807 DOI: 10.1063/1.5079419] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 02/12/2019] [Indexed: 11/14/2022] Open
Abstract
In situ inventory of sulfurous products from the sulfur K-edge synchrotron X-radiolysis of l-cysteine in solid-phase and anaerobic (pH 5) and air-saturated (pH 5, 7, and 9) solutions without and with 40% glycerol is reported. Sequential K-edge X-ray Absorption Spectroscopic (XAS) spectra were acquired. l-cysteine degraded systematically in the X-ray beam. Radiolytic products were inventoried by fits using the XAS spectra of sulfur model compounds. Solid l-cysteine declined to 92% fraction after a single K-edge XAS scan. After six scans, 60% remained, accompanied by 14% cystine, 16% thioether, 5.4% elemental sulfur, and smaller fractions of more highly oxidized products. In air-saturated pH 5 solution, 73% of l-cysteine remained after ten scans, with 2% cystine and 19% elemental sulfur. Oxidation increased with 40% glycerol, yielding 67%, 5%, and 23% fractions, respectively, after ten scans. Higher pH solutions exhibited less radiolytic chemistry. All the reactivity followed first-order kinetics. The anaerobic experiment displayed two reaction phases, with sharp changes in kinetics and radiolytic chemistry. Unexpectedly, the radiolytic oxidation of l-cysteine was increased in anaerobic solution. After ten scans, only 60% of the l-cysteine remained, along with 17% cystine, 22% elemental sulfur, and traces of more highly oxidized products. A new aerobic reaction cycle is hypothesized, wherein dissolved dioxygen captures radiolytic H• or eaq -, enters HO2 •/O2 •-, reductively quenches cysteine thiyl radicals, and cycles back to O2. This cycle is suggested to suppress the radiolytic production of cystine in aerobic solution.
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Affiliation(s)
- Patrick Frank
- Author to whom correspondence should be addressed: . Tel.: 650-723-2479
| | - Ritimukta Sarangi
- Stanford Synchrotron Radiation Lightsource, SLAC, Stanford University, Menlo Park, California 94025, USA
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC, Stanford University, Menlo Park, California 94025, USA
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8
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Levina A, Crans DC, Lay PA. Speciation of metal drugs, supplements and toxins in media and bodily fluids controls in vitro activities. Coord Chem Rev 2017. [DOI: 10.1016/j.ccr.2017.01.002] [Citation(s) in RCA: 112] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/09/2022]
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Pickering IJ, Barney M, Cotelesage JJH, Vogt L, Pushie MJ, Nissan A, Prince RC, George GN. Chemical Sensitivity of the Sulfur K-Edge X-ray Absorption Spectra of Organic Disulfides. J Phys Chem A 2016; 120:7279-86. [DOI: 10.1021/acs.jpca.6b06790] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Ingrid J. Pickering
- Molecular
and Environmental Sciences Group, Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada
- Department
of Chemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5C9, Canada
| | - Monica Barney
- Chevron Energy Technology Company, Richmond, California 94802, United States
| | - Julien J. H. Cotelesage
- Molecular
and Environmental Sciences Group, Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada
| | - Linda Vogt
- Molecular
and Environmental Sciences Group, Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada
- Department
of Chemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5C9, Canada
| | - M. Jake Pushie
- Molecular
and Environmental Sciences Group, Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada
| | - Andrew Nissan
- Chevron Energy Technology Company, Richmond, California 94802, United States
| | - Roger C. Prince
- ExxonMobil Biomedical Sciences, Inc., Annandale, New Jersey 08801, United States
| | - Graham N. George
- Molecular
and Environmental Sciences Group, Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada
- Department
of Chemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5C9, Canada
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Abstract
1. Thianthrene is a sulfur-containing tricyclic molecule distributed widely within the macrostructure of hydrocarbon fossil fuels. Identified nearly 150 years ago, its chemistry has been widely explored leading to insights into reaction mechanisms and radical ion formation. 2. It has been claimed to have therapeutic application in the treatment of dermal infections and to interfere with enzyme and nucleic acid function, but appears to have little toxicity. 3. Following its oral administration to the rat, the majority remained within the gastrointestinal tract. After three days, about 88% was detected in the combined excreta with the remainder still within the animal. It is readily taken up into fish from the surrounding aqueous environment and has been placed within the "bioaccumulative category" to be regarded with concern. 4. Mammalian metabolism appeared to be restricted to ring carbon oxidation and subsequent glucuronic acid conjugation. Small amounts of sulfoxide and disulfoxide were also formed. No ring degradation was evident. Microorganisms similarly undertook aromatic ring hydroxylation but were able also to rupture the ring system by attacking the carbon-sulfur linkages and thereby degrading the molecule.
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Affiliation(s)
- Steve C Mitchell
- a Computational and Systems Medicine, Imperial College London , London , UK and
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Leblanc C, Vilter H, Fournier JB, Delage L, Potin P, Rebuffet E, Michel G, Solari P, Feiters M, Czjzek M. Vanadium haloperoxidases: From the discovery 30 years ago to X-ray crystallographic and V K-edge absorption spectroscopic studies. Coord Chem Rev 2015. [DOI: 10.1016/j.ccr.2015.02.013] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Kustin K. Aqueous vanadium ion dynamics relevant to bioinorganic chemistry: A review. J Inorg Biochem 2014; 147:32-8. [PMID: 25578410 DOI: 10.1016/j.jinorgbio.2014.12.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Revised: 12/05/2014] [Accepted: 12/05/2014] [Indexed: 10/24/2022]
Abstract
Aqueous solutions of the four highest vanadium oxidation states exhibit four diverse colors, which only hint at the diverse reactions that these ions can undergo. Cationic vanadium ions form complexes with ligands; anionic vanadium ions form complexes with ligands and self-react to form isopolyanions. All vanadium species undergo oxidation-reduction reactions. With a few exceptions, elucidation of the dynamics of these reactions awaited the development of fast reaction techniques before the kinetics of elementary ligation, condensation, reduction, and oxidation of the aqueous vanadium ions could be investigated. As the biological roles played by endogenous and therapeutic vanadium expand, it is appropriate to bring the results of the diverse kinetics studies under one umbrella. To achieve this goal this review presents a systematic examination of elementary aqueous vanadium ion dynamics.
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Affiliation(s)
- Kenneth Kustin
- Department of Chemistry, Emeritus, MS015, Brandeis University, Waltham, MA 02454, USA.
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George GN, Hackett MJ, Sansone M, Gorbaty ML, Kelemen SR, Prince RC, Harris HH, Pickering IJ. Long-range chemical sensitivity in the sulfur K-edge X-ray absorption spectra of substituted thiophenes. J Phys Chem A 2014; 118:7796-802. [PMID: 25116792 PMCID: PMC4161161 DOI: 10.1021/jp505766f] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
Thiophenes are the simplest aromatic
sulfur-containing compounds
and are stable and widespread in fossil fuels. Regulation of sulfur
levels in fuels and emissions has become and continues to be ever
more stringent as part of governments’ efforts to address negative
environmental impacts of sulfur dioxide. In turn, more effective removal
methods are continually being sought. In a chemical sense, thiophenes
are somewhat obdurate and hence their removal from fossil fuels poses
problems for the industrial chemist. Sulfur K-edge X-ray absorption
spectroscopy provides key information on thiophenic components in
fuels. Here we present a systematic study of the spectroscopic sensitivity
to chemical modifications of the thiophene system. We conclude that
while the utility of sulfur K-edge X-ray absorption spectra in understanding
the chemical composition of sulfur-containing fossil fuels has already
been demonstrated, care must be exercised in interpreting these spectra
because the assumption of an invariant spectrum for thiophenic forms
may not always be valid.
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Affiliation(s)
- Graham N George
- Molecular and Environmental Sciences Group, Department of Geological Sciences, University of Saskatchewan , Saskatoon, Saskatchewan S7N 5E2, Canada
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