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Sökning: swepub > Umeå universitet > Refereegranskat > (2000-2004) > Pettersson Lage

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11.
  • Pettersson, Lage, et al. (författare)
  • 17O NMR study of aqueous peroxoisopolymolybdate equilibria at lower peroxide/Mo ratios
  • 2003
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; , s. 146-52
  • Tidskriftsartikel (refereegranskat)abstract
    • Aqueous peroxomolybdates have been studied using 17O NMR together with equilibrium measurements and calculations, over a wide range of conditions. Ten peroxo species are identified, mostly in more than one state of protonation. Some are already known in the solid state, or from equilibrium analysis, but structural information is also obtained for MoO3(HO2)– and the new or previously tentative species Mo2O5(O2)22–, HpMo7O23(O2)2p–6 and HpMo7O23(O2)p–6(p= 0–2). Sites of protonation are identified, as are 17O resonances from both bidentate and monodentate peroxide. Several oxygen exchange processes are also seen, including a probable dimer–tetramer exchange.
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12.
  • Pettersson, Lage, et al. (författare)
  • Speciation in peroxovanadate systems
  • 2003
  • Ingår i: Coordination Chemistry Reviews. ; 237:1-2, s. 77-87
  • Tidskriftsartikel (refereegranskat)abstract
    • Detailed and thorough potentiometric and 51V-NMR spectroscopic investigations of H+–H2VO4−–H2O2–Ligand systems have been performed at 25 °C in 0.15 M Na(Cl) ionic medium. Extensive ranges of vanadate, hydrogen peroxide and ligand concentration and of pH have been covered. The medium was chosen to represent the physiological conditions in human blood. The computer program , designed to treat different types of data simultaneously, has been used to establish the entire speciation in the systems. Before studying systems containing the ligand (L), the complete speciation in the subsystem H+–H2VO4−–H2O2 must be known under the same experimental conditions. The formation constants in this subsystem have earlier been determined and it was found that hydrogen peroxide interacts with vanadate in the whole pH range studied (0.5–10.5). In all, 10 peroxovanadate species were identified and diperoxovanadate species were found to be exceptionally stable at physiological pH. The ligands studied so far include imidazole (Im), -α-alanyl--histidine (Ah), -α-alanyl--serine (As), picolinic acid (Pi), and -(+)-lactic acid (La). In these five systems, as many as 3, 8, 6, 8, and 5 different peroxovanadate—L species (isomers included) were identified. A feature common to all these systems is that V(H2O2)2L species are formed at physiological pH. Notably, the 51V chemical shift values of diperoxovanadate moieties are always found in the range −670 to −770 ppm, and those of monoperoxovanadate from −540 to −670 ppm. The equilibrium conditions are illustrated in distribution diagrams and the effectiveness of the different ligands as complexation agents are compared. In the case of diperoxovanadate complexes, ligands with aromatic nitrogen (Im, Pi, Ah) are the most effective, the one with both aliphatic nitrogen and oxygen (As) is less effective, and the one with oxygen only (La) is the least preferred.
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13.
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14.
  • Schmidt, Hauke, et al. (författare)
  • A Potentiometric and 51V NMR Study of the Aqueous H+/H2VO4-/H2O2/l--Alanyl-l-histidine System
  • 2001
  • Ingår i: Chemistry. ; 7:1, s. 251-7
  • Tidskriftsartikel (refereegranskat)abstract
    • The speciation in the quaternary aqueous H+/H2VO4-/H2O2/l--alanyl-l-histidine (Ah) system has been determined from quantitative 51V NMR measurements and potentiometric data (glass electrode). The study was performed in 0.150 m Na(Cl) medium at 25 °C. Data were evaluated with the computer program LAKE, which is able to treat combined EMF and NMR data. The pKa values for Ah were determined as 8.06, 6.72 and 2.64. In the ternary H+/H2VO4-/Ah system, two complexes, (H+)p(H2VO4-)q(Ah)r, for which (p, q, r) values of (0, 1, 1) and (1, 1, 1) with log 0,1,1=2.52±0.03 and log 1,1,1=9.40±0.05 (pKa=6.88), respectively, explain all data. The errors given are 3. In the quaternary H+/H2VO4-/H2O2/Ah system, eight complexes were determined in addition to all binary and ternary complexes, four with a V/X/Ah ratio 1:1:1 and four with a ratio 1:2:1 (X=peroxo ligand). VX2Ah2- and VX2Ah- (pKa=8.19) are the main complexes and predominate in the pH range 5 to 9. Three additional minor species have also been found but their compositions could not be determined owing to their small amounts. Equilibria are slow, significant decomposition of peroxide occurs only in acidic solutions. Data in the pH range 5 to 10 have been used for the LAKE calculations. Chemical shifts, compositions, and formation constants for the eight quaternary complexes are given, and equilibrium conditions are illustrated in distribution diagrams. Structural proposals for VX2Ah2- and VX2Ah- are made from 1H and 13C NMR measurements.
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15.
  • Schmidt, Hauke, et al. (författare)
  • Short Communication : [CA1]Speciation in the vanadate–alanylhistidine–peroxide system
  • 2000
  • Ingår i: Journal of Inorganic Biochemistry. ; 80:1-2, s. 149-151
  • Tidskriftsartikel (refereegranskat)abstract
    • The speciation in the quaternary aqueous H+–H2VO4−–H2O2–-α-alanyl--histidine (Ah) system has been determined from quantitative 51V NMR measurements and potentiometric data (glass electrode). The study was performed in 0.150 M Na(Cl) medium at 25 °C. Data were evaluated with the computer program LAKE, which is able to treat combined potentiometric and NMR data. In the ternary H+–H2VO4−–Ah system, two complexes, (H+)p(H2VO4−)q(Ah)r, having (p, q, r) values (0, 1, 1) and (1, 1, 1) (pKa=6.88) explain all data. In the quaternary H+–H2VO4−–H2O2–Ah system, seven complexes were determined in addition to all binary and ternary complexes, four with a V/X/Ah ratio 1:1:1 and three with a ratio 1:2:1 (X=peroxo ligand). VX2Ah2− and VX2Ah− (pKa=8.26) are the main quaternary complexes and predominate in the pH range 5 to 9. Chemical shifts, compositions and formation constants for all the quaternary complexes are given, and equilibrium conditions are illustrated in distribution diagrams.
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16.
  • Selling, Anna, et al. (författare)
  • Multicomponent Polyanions, 49 : A Potentiometric and (31P, 51V) NMR Study of the Aqueous Molybdovanadophosphate System
  • 2000
  • Ingår i: European Journal of Inorganic Chemistry. ; 7, s. 1509-21
  • Tidskriftsartikel (refereegranskat)abstract
    • The equilibrium speciation of the quaternary system H+/MoO42-/HVO42-/HPO42- in aqueous 0.600 M Na(Cl) at 25 °C and 90 °C was studied by pH potentiometry and 31P (202.5 MHz) and 51V (131.6 MHz) NMR spectrometry. The study focused on solutions containing the oxoanion components in the ratios (Mo + V)/P = 12:1 and Mo/V 3.8, in the pH range 0-5, wherein Keggin anions of the formula [HzMo12-xVxPO40](3+x-z)- with x = 1-3 are the predominant species. Formation constants (log ) and pKa values for Keggin anions with x = 1-3 were determined from 31P and 51V resonance chemical shift data, 31P resonance intensity data, and pH potentiometric data with the multidata least squares calculation program LAKE. The [Mo11VPO40]4- anion does not protonate, [Mo10V2PO40]5- anions can be monoprotonated, and [Mo9V3PO40]6- anions can be triprotonated. The six most intense 31P NMR resonances of [HzMo9V3PO40](6 - z)- could be followed over the pH range studied. It was also possible to assign some 31P resonances to a specific isomer of [Mo9V3PO40]6-.
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17.
  • Selling, Anna, et al. (författare)
  • Reduced molybdovanadophosphates
  • 2002
  • Ingår i: European Journal of Inorganic Chemistry. - 1434-1948. ; :3, s. 743-9
  • Tidskriftsartikel (refereegranskat)abstract
    • The equilibrium speciation in the aqueous H+/MoO42-/ HVO42-/HPO42-/e(-) system, 0.600 M Na(CI) medium at 25 degreesC, was characterised by potentiometric [H+] (glass electrode) and {epsilon(-)} (platinum electrode) titration techniques as fundamental tools, complemented by V-51(V) NMR (131.6 MHz) and V-IV ESR spectroscopy. The study has been focused on solutions with the Keggin ratio, (Mo + V)/P = 12:1 and Mo/V > 5, in the pH range 1.4-4,5, where anions having the formula [(HzMo12-x-yVxVyPO40)-V-V-P-IV]((3+x+2y-z)-) are predominant species. Added numbers of electrons per vanadium(V) (e(-)/V-V) have been kept less than one to exclude reduction of molybdenum(VI). Six reduced molybdovanadophosphate species have been identified. The [(MO11VPO40)-P-IV](5-) species [logbeta = 154.15 +/- 0.03 (3sigma)] and the mixed-valence species [(Mo10VVPO40)-V-V-P-IV](6-) (logbeta = 155.84 +/- 0.02) can both be monoprotonated, These species have pK(a) values of 0.93 and 3.68, respectively. A "fully" reduced Keggin species, [(H2Mo10V2PO40)-P-IV](5-) (logbeta = 171.27 +/- 0.06), and a lacunary [(H4Mo10VPO39)-P-IV](5-) species (logbeta = 142.0 +/- 0.2) were found as well. Except for the molybdovanadophosphate species, the only reduced species formed, in the present investigation, is the vanadyl ion, VO2+. logK(red) (2 H+ + VO2+ + e reversible arrow VO2+ + H2O) was deterinined to 17.15 +/- 0.01 (E-0 = 1014.5 +/- 0.6 mV).
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18.
  • Taube, Fabian, et al. (författare)
  • Characterisation of aqueous peroxomolybdate catalysts applicable to pulp bleaching
  • 2002
  • Ingår i: Journal of the Chemical Society. Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1472-7773 .- 1364-5447. ; , s. 1002-1008
  • Tidskriftsartikel (refereegranskat)abstract
    • The equilibrium speciation in the system pH++qMoO42–+rH2O2+sSO42– (H+)p(MoO42–)q(H2O2)r(SO42–)s in 0.300 M Na2(SO4) medium at 25 °C has been determined from potentiometric titration data in the ranges 2.0 pH 5.5, 5.00 [Mo]tot/mM 80.00, 0 [H2O2]tot/mM 245 and 273.07 [SO42–]tot/mM 320.20. Species with the following compositions were found: MoX– (1,1,1,0), MoX (2,1,1,0), MoX2– (1,1,2,0), MoX2 (2,1,2,0), MoX2S2– (2,1,2,1), Mo2X42– (2,2,4,0), Mo7X6– (8,7,1,0), Mo7X5– (9,7,1,0), Mo7X4– (10,7,1,0) and Mo7X3– (11,7,1,0). The numbers in parentheses refer to the values of p, q, r and s in the formula above. The numbers and charges of molybdenum (Mo), peroxide (X) and sulfate (S) in each species are given in the abbreviated formula MoqXrSs(2q+ 2s–p)–. The following formation constants with 3 were obtained; log1,1,1,0= 8.53 ± 0.03, log2,1,1,0= 11.22 ± 0.04 (pKa= 2.69), log1,1,2,0= 11.61 ± 0.03, log2,1,2,0= 13.77 (± 0.06) (pKa= 2.16), log2,1,2,1= 14.50 ± 0.06, log2,2,4,0= 23.77 ± 0.11, log8,7,1,0= 56.71 ± 0.11, log9,7,1,0= 62.00 ± 0.05 (pKa= 5.29), log10,7,1,0= 65.74 ± 0.06 (pKa= 3.74), log11,7,1,0= 68.23 ± 0.08 (pKa= 2.49). Most complexes have been verified by 95Mo NMR, 17O NMR, and the novel MoX2S2– complex also by FTIR spectroscopy.
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19.
  • Taube, Fabian, et al. (författare)
  • Equilibria and dynamics of some aqueous peroxomolybdate catalysts: a 17O NMR spectroscopic study
  • 2002
  • Ingår i: Journal of the Chemical Society. Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1472-7773 .- 1364-5447. ; , s. 4451-6
  • Tidskriftsartikel (refereegranskat)abstract
    • The equilibrium speciation at 278 K and the dynamics in the systems pH++qMoO42–+rH2O2+sL (H+)p(MoO42–)q(H2O2)r Ls(L = SO42– or Cl–) in 0.3 M Na2(SO4) and 0.6 M Na(Cl) medium has been determined from 17O NMR integral and shift data in the range 0.7 pH 4.1 and at excess of peroxide ([H2O2]tot/[Mo]tot= 3). In 0.3 M Na2(SO4) medium species with the following compositions were found: MoX2–(1,1,2,0), MoX2(2,1,2,0), MoX2S2–(2,1,2,1), MoX2S–(3,1,2,1), Mo2X42–(2,2,4,0), Mo2X4–(3,2,4,0) and Mo2X62–(2,2,6,0), where (Mo) corresponds to MoO42–, (X) to O22– or HOO– and (S) to SO42–. In 0.6 M Na(Cl) medium the diperoxomolybdosulfate complex MoX2S– is replaced with a novel diperoxomolybdochloride complex MoX2Cl–(2,1,2,1), where (Cl) corresponds to Cl–. The numbers in parentheses refer to the values of p,q,r and s in the formula above. The stoichiometries of each complex are given by the abbreviated formula MoqXrSs(2q+ 2s–p)– and MoqXrCls(2q+s–p)–. The following formation constants with 3 were obtained with values for 0.6 M Na(Cl) in parenthesis: log 1,1,2,0= 11.61 (11.61); log 2,1,2,0= 13.70 ± 0.10, pKa= 2.09 (13.86 ± 0.10, pKa= 2.25); log 2,1,2,1= 14.57 ± 0.07 (13.87 ± 0.15 ); log 3,1,2,1= 15.27 ± 0.17, pKa= 0.70, log 2,2,4,0= 24.06 ± 0.05 (24.08 ± 0.04); log 3,2,4,0= 25.99 ± 0.18, pKa= 1.93 (26.23 ± 0.17, pKa= 2.15); log 2,2,6,0= 24.02 ± 0.15 (23.9 ± 0.3). The pKa value for HSO4– was determined to be 1.06 ± 0.11. At 278 K the MoX2 and Mo2X4 complexes are in chemical exchange and the rate of exchange increases upon protonation. At 312 K there is also measurable exchange between MoX2S and the MoX2 and Mo2X4 complexes. The dynamics in 0.6 M Na(Cl) medium seem to be very similar to those in the sulfate medium.
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20.
  • Taube, Fabian, et al. (författare)
  • Equilibria and dynamics of some aqueous peroxomolybdophosphate catalysts: a potentiometric and 31P NMR spectroscopic study
  • 2003
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; , s. 2512-2518
  • Tidskriftsartikel (refereegranskat)abstract
    • The equilibrium speciation in the pH++qMoO42–+rH2O2+sH2PO4–+tSO42–(H+)p(MoO42–)q(H2O2)r(H2PO4–)s(SO42–)tp–2q–s–2t system in 0.300 M Na2(SO4) medium at 25 °C and [H2O2]tot/[Mo]tot > 2 has been determined from potentiometric data and 31P NMR integral and chemical shift data in the range 1.0 pH 9.0, 2.0 [MoO42–]tot/mM 293, 32 [H2O2]tot/mM 640, 2 [H2PO4–]tot/mM 60 and 200 [SO42–]tot/mM 380. Species with the following compositions were obtained: MoX2P3–(0,1,2,1,0), MoX2P2–(1,1,2,1,0), MoX2P–(2,1,2,1,0), Mo2X4P3–(2,2,4,1,0), Mo2X4P2–(3,2,4,1,0), Mo3X6P3–(4,3,6,1,0), Mo3X6P2–(5,3,6,1,0) and Mo4X8P3–(6,4,8,1,0). The numbers and charges of molybdenum (Mo), peroxide (X), phosphate (P) and sulfate (S) in each species are given in the abbreviated formula MoqXrPsStp–2q–s–2t. The numbers in parentheses refer to the values of p, q, r, s and t in the formula above. The following formation constants with 3 were obtained; log0,1,2,1,0= 5.16 ± 0.09, log1,1,2,1,0= 12.73 ± 0.02 (pKa= 7.63), log2,1,2,1,0= 16.14 ± 0.03 (pKa= 3.42), log2,2,4,1,0= 25.03 (± 0.04), log3,2,4,1,0= 29.54 ± 0.02 (pKa= 4.51), log4,3,6,1,0= 42.30 ± 0.03, log5,3,6,1,0= 44.06 ± 0.08 (pKa= 1.76), log6,4,8,1,0= 57.30 ± 0.07. pKa values for H3PO4 and H2PO4– were determined to 2.00 and 6.48, respectively. Chemical exchange processes were detected by 31P NMR 2D EXSY and selective magnetisation transfer experiments between the complexes. An averaged lifetime, (X2Mo–OP) 30 ms, can be estimated for the MoX2P and Mo2X4P species at pH = 5.5 and 5 °C.
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