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Zanonato, P. L., Di Bernardo, P., Vallet, V., Szabo, Z. & Grenthe, I. (2015). Alkali-metal ion coordination in uranyl(VI) poly-peroxide complexes in solution. Part 1: the Li+, Na+ and K+ - peroxide-hydroxide systems. Dalton Transactions, 44(4), 1549-1556
Open this publication in new window or tab >>Alkali-metal ion coordination in uranyl(VI) poly-peroxide complexes in solution. Part 1: the Li+, Na+ and K+ - peroxide-hydroxide systems
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2015 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 44, no 4, p. 1549-1556Article in journal (Refereed) Published
Abstract [en]

The alkali metal ions Li+, Na+ and K+ have a profound influence on the stoichiometry of the complexes formed in uranyl(VI)-peroxide-hydroxide systems, presumably as a result of a templating effect, resulting in the formation of two complexes, M[(UO2)(O-2)(OH)](2)(-) where the uranyl units are linked by one peroxide bridge, mu-eta(2)-eta(2), with the second peroxide coordinated "end-on", eta(2), to one of the uranyl groups, and M[(UO2)(O-2)(OH)](4)(3-), with a four-membered ring of uranyl ions linked by mu-eta(2)-eta(2) peroxide bridges. The stoichiometry and equilibrium constants for the reactions: M+ + 2UO(2)(2+) + 2HO(2)(-) + 2H(2)O -> M[(UO2)(O-2)(OH)] 2 - + 4H(+) (1) and M+ + 4UO(2)(2+) + 4HO(2)(-) + 4H(2)O -> M[(UO2)(O-2)(OH)](4)(3-) + 8H(+) (2) have been measured at 25 degrees C in 0.10 M (tetramethyl ammonium/M+)NO3 ionic media using reaction calorimetry. Both reactions are strongly enthalpy driven with large negative entropies of reaction; the observation that Delta H(2) approximate to 2 Delta H(1) suggests that the enthalpy of reaction is approximately the same when peroxide is added in bridging and "end-on" positions. The thermodynamic driving force in the reactions is the formation of strong peroxide bridges and the role of M+ cations is to provide a pathway with a low activation barrier between the reactants and in this way "guide" them to form peroxide bridged complexes; they play a similar role as in the synthesis of crown-ethers. Quantum chemical (QC) methods were used to determine the structure of the complexes, and to demonstrate how the size of the M+-ions affects their coordination geometry. There are several isomers of Na[(UO2)(O-2)(OH)](2)(-) and QC energy calculations show that the ones with a peroxide bridge are substantially more stable than the ones with hydroxide bridges. There are isomers with different coordination sites for Na+ and the one with coordination to the peroxide bridge and two uranyl oxygen atoms is the most stable one.

Keywords
Water Exchange-Reaction, Basis-Sets, Chemical-Equilibria, Free-Energy, Solvation, Pseudopotentials, Hydrogen, Atoms
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-159355 (URN)10.1039/c4dt02104e (DOI)000346907800008 ()2-s2.0-84919933637 (Scopus ID)
Note

QC 20150202

Available from: 2015-02-02 Created: 2015-01-29 Last updated: 2017-12-05Bibliographically approved
Zanonato, P., Szabó, Z., Vallet, V., Di Bernardo, P. & Grenthe, I. (2015). Alkali-metal ion coordination in uranyl(VI) poly-peroxo complexes in solution, inorganic analogues to crown-ethers. Part 2. Complex formation in the tetramethyl ammonium-, Li+-, Na+- and K+-uranyl(VI)-peroxide-carbonate systems. Dalton Transactions, 44(37), 16565-16572
Open this publication in new window or tab >>Alkali-metal ion coordination in uranyl(VI) poly-peroxo complexes in solution, inorganic analogues to crown-ethers. Part 2. Complex formation in the tetramethyl ammonium-, Li+-, Na+- and K+-uranyl(VI)-peroxide-carbonate systems
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2015 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 44, no 37, p. 16565-16572Article in journal (Refereed) Published
Abstract [en]

The constitution and equilibrium constants of ternary uranyl(VI) peroxide carbonate complexes [(UO2)(p)(O-2)(q)(CO3)(r)](2(p-q-r)) have been determined at 0 degrees C in 0.50 M MNO3, M = Li, K, and TMA (tetramethyl ammonium), ionic media using potentiometric and spectrophotometric data; O-17 NMR data were used to determine the number of complexes present. The formation of cyclic oligomers, "[(UO2)(O-2)(CO3)](n)", n = 4, 5, 6, with different stoichiometries depending on the ionic medium used, suggests that Li+, Na+, K+ and TMA ions act as templates for the formation of uranyl peroxide rings where the uranyl-units are linked by mu-eta(2)-eta(2) bridged peroxide-ions. The templating effect is due to the coordination of the M+-ions to the uranyl oxygen atoms, where the coordination of Li+ results in the formation of Li[(UO2)(O-2)(CO3)](4)(7-), Na+ and K+ in the formation of Na/K[(UO2)(O-2)(CO3)](5)(9-) complexes, while the large tetramethyl ammonium ion promotes the formation of two oligomers, TMA[(UO2)(O-2)(CO3)] 5 9-and TMA[(UO2)(O-2)(CO3)](6)(11-). The NMR spectra demonstrate that the coordination of Na+ in the five-and six-membered oligomers is significantly stronger than that of TMA(+); these observations suggest that the templating effect is similar to the one observed in the synthesis of crown-ethers. The NMR experiments also demonstrate that the exchange between TMA[(UO2)(O-2)(CO3)](5)(9-) and TMA[(UO2)(O-2)(CO3)](6)(11-) is slow on the O-17 chemical shift time-scale, while the exchange between TMA[(UO2)(O-2)(CO3)](6)(11-)and Na[(UO2)(O-2)(CO3)](6)(11-) is fast. There was no indication of the presence of large clusters of the type identified by Burns and Nyman (M. Nyman and P. C. Burns, Chem. Soc. Rev., 2012, 41, 7314-7367) and possible reasons for this and the implications for the synthesis of large clusters are briefly discussed.

National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:kth:diva-174609 (URN)10.1039/c5dt01710f (DOI)000361544500042 ()2-s2.0-84941773441 (Scopus ID)
Note

QC 20151207

Available from: 2015-12-07 Created: 2015-10-07 Last updated: 2017-12-01Bibliographically approved
Vallet, V., Zanonato, P. L., Di Bernardo, P., Szabo, Z. & Grenthe, I. (2015). Experimental and quantum chemical studies of alkali-ion promoted formation of uranyl(VI) peroxide rings and a comparison with similar reactions in 12-crown-5 and 15-crown-5 systems. Abstract of Papers of the American Chemical Society, 249
Open this publication in new window or tab >>Experimental and quantum chemical studies of alkali-ion promoted formation of uranyl(VI) peroxide rings and a comparison with similar reactions in 12-crown-5 and 15-crown-5 systems
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2015 (English)In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 249Article in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2015
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-243700 (URN)000411186502715 ()
Note

QC 20190227

Available from: 2019-02-27 Created: 2019-02-27 Last updated: 2019-02-27Bibliographically approved
Fatih Polat, M., Hettmanczyk, L., Zhang, W., Szabo, Z. & Franzén, J. (2013). One-Pot, Two-Step Protocol for the Catalytic Asymmetric Synthesis of Optically Active N,O- and O,O-Acetals. ChemCatChem, 5(6), 1334-1339
Open this publication in new window or tab >>One-Pot, Two-Step Protocol for the Catalytic Asymmetric Synthesis of Optically Active N,O- and O,O-Acetals
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2013 (English)In: ChemCatChem, ISSN 1867-3880, E-ISSN 1867-3899, Vol. 5, no 6, p. 1334-1339Article in journal (Refereed) Published
Keywords
Acetals, Asymmetric catalysis, Conjugate addition, Heterocycles, Organocatalysis
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-134274 (URN)10.1002/cctc.201200860 (DOI)000319680800017 ()2-s2.0-84878499424 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20131125

Available from: 2013-11-25 Created: 2013-11-20 Last updated: 2017-05-30Bibliographically approved
Giesecke, M., Szabo, Z. & Furo, I. (2013). The protonation state and binding mode in a metal coordination complex from the charge measured in solution by electrophoretic NMR. Analytical Methods, 5(7), 1648-1651
Open this publication in new window or tab >>The protonation state and binding mode in a metal coordination complex from the charge measured in solution by electrophoretic NMR
2013 (English)In: Analytical Methods, ISSN 1759-9660, E-ISSN 1759-9679, Vol. 5, no 7, p. 1648-1651Article in journal (Refereed) Published
Abstract [en]

We measured with high accuracy the effective charge of a uranium (VI)-AMP complex by electrophoretic NMR (eNMR). Using the same method, the degree of counterion association is also assessed which leads to a quantitative determination of the nominal charge which then provides the degree of ligand deprotonation in the complex. This demonstrates a new application of eNMR for resolving structural details of supramolecular complexes.

Keywords
Multinuclear Nmr, Stability-Constants, Uranyl Acetate, Ions, Polyelectrolytes, Nucleotides, Uranium, Cells
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-120562 (URN)10.1039/c3ay00023k (DOI)000316118500002 ()2-s2.0-84879538166 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20130412

Available from: 2013-04-12 Created: 2013-04-11 Last updated: 2017-12-06Bibliographically approved
Zanonato, P. L., Di Bernardo, P., Szabo, Z. & Grenthe, I. (2012). Chemical equilibria in the uranyl(VI)-peroxide-carbonate system: identification of precursors for the formation of poly-peroxometallates. Dalton Transactions, 41(38), 11635-11641
Open this publication in new window or tab >>Chemical equilibria in the uranyl(VI)-peroxide-carbonate system: identification of precursors for the formation of poly-peroxometallates
2012 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 41, no 38, p. 11635-11641Article in journal (Refereed) Published
Abstract [en]

The focus of this study is on the identification of precursors in solution that might act as building blocks when solid uranyl(VI) poly-peroxometallate clusters containing peroxide and hydroxide bridges are formed. The precursors could be identified by using carbonate as an auxiliary ligand that prevented the formation of large clusters, such as the ones found in solids of fullerene type. Using data from potentiometric and NMR (O-17 and C-13) experiments we identified the following complexes and determined their equilibrium constants: (UO2)(2)(O-2)(CO3)(4)(6-), UO2(O-2)CO32-, UO2(O-2)(CO3)(2)(4-), (UO2)(2)(O-2)(CO3)(2)(2-), (UO2)(2)(O-2)(2)(CO3)(2-) and [UO2(O-2)(CO3)(5)(10-). The NMR spectra of the pentamer show that all uranyl and carbonate sites are equivalent, which is only consistent with a ring structure built from uranyl units linked by peroxide bridges with the carbonate coordinated "outside" the ring; this proposed structure is very similar to [UO2(O-2)(oxalate)](5)(10-) identified by Burns et al. (J. Am. Chem. Soc., 2009, 131, 16648; Inorg. Chem., 2012, 51, 2403) in K-10[UO2(O-2)(oxalate)](5)center dot(H2O)(13); similar ring structures where oxalate or carbonate has been replaced by hydroxide are important structure elements in solid poly-peroxometallate complexes. The equivalent uranyl sites in (UO2)(2)(O-2)(2)(CO3)(2-) suggest that the uranyl-units are linked by the carbonate ion and not by peroxide.

Keywords
Uranyl-Peroxide Nanoclusters, Clusters
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-103780 (URN)10.1039/c2dt31282d (DOI)000308655800016 ()2-s2.0-84870861313 (Scopus ID)
Note

QC 20121019

Available from: 2012-10-19 Created: 2012-10-19 Last updated: 2017-12-07Bibliographically approved
Szabo, Z. & Grenthe, I. (2011). (17)O NMR study of the oxygen exchange between uranyl(VI) oxygen and water oxygen in acidic and strongly alkaline solutions. Abstract of Papers of the American Chemical Society, 242, 102-NUCL
Open this publication in new window or tab >>(17)O NMR study of the oxygen exchange between uranyl(VI) oxygen and water oxygen in acidic and strongly alkaline solutions
2011 (English)In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 242, p. 102-NUCL-Article in journal (Other academic) Published
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-90178 (URN)000299378304767 ()
Note
QC 20120220Available from: 2012-02-20 Created: 2012-02-20 Last updated: 2017-12-07Bibliographically approved
Vallet, V., Szabo, Z. & Grenthe, I. (2011). Structure and dynamics of binary and ternary lanthanide(III) and actinide(III) tris[4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione] (TTA) - tributylphosphate (TBP) complexes.: Part 3, the structure, thermodynamics and reaction mechanisms of 8-and 9-coordinated binary and ternary Y-TTA-TBP complexes studied by quantum chemical methods. Dalton Transactions, 40(13), 3154-3165
Open this publication in new window or tab >>Structure and dynamics of binary and ternary lanthanide(III) and actinide(III) tris[4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione] (TTA) - tributylphosphate (TBP) complexes.: Part 3, the structure, thermodynamics and reaction mechanisms of 8-and 9-coordinated binary and ternary Y-TTA-TBP complexes studied by quantum chemical methods
2011 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 40, no 13, p. 3154-3165Article in journal (Refereed) Published
Abstract [en]

Possible mechanisms for intermolecular exchange between coordinated and solvent water in the complexes Y(TTA)(3)(OH2)(2) and Y(TTA)(3)(TBP)(OH2) and intermolecular exchange between free and coordinated HTTA in Y(TTA)(3)(OH2)(HTTA) and Y(TTA)(3)(TBP)(HTTA) have been investigated using ab initio quantum chemical methods. The calculations comprise both structures and energies of isomers, intermediates and transition states. Based on these data and experimental NMR data (Part 2) we have suggested intimate reaction mechanisms for water exchange, intramolecular exchange between structure isomers and intermolecular exchange between free HTTA and coordinated TTA. A large number of isomers are possible for the complexes investigated, but only some of them have been investigated, in all of them the most stable geometry is a more or less distorted square anti-prism or bicapped trigonal prism; the energy differences between the various isomers are in general small, less than 10 kJ mol(-1). 9-coordinated intermediates play an important role in all reactions. Y(TTA)(3)(OH2)(3) has three non-equivalent water ligands that can participate in ligand exchange reactions. The fastest of these exchanging sites has a QM activation energy of 18.1 kJ mol(-1), in good agreement with the experimental activation enthalpy of 19.6 kJ mol(-1). The mechanism for the intramolecular exchange between structure isomers in Y(TTA)(3)(OH2)(2) involves the opening of a TTA-ring as the rate determining step as suggested by the good agreement between the QM activation energy and the experimental activation enthalpy 47.8 and 58.3 J mol(-1), respectively. The mechanism for the intermolecular exchange between free and coordinated HTTA in Y(TTA)(3)(HTTA) and Y(TTA)(3)(TBP)(HTTA) involves the opening of the intramolecular hydrogen bond in coordinated HTTA followed by proton transfer to coordinated TTA. This mechanism is supported by the good agreement between experimental activation enthalpies (within parenthesis) and calculated activation energies 68.7 (71.8) and 35.3 (38.8) kJ mol(-1). The main reason for the difference between the two systems is the much lower energy required to open the intramolecular hydrogen bond in the latter. The accuracy of the QM methods and chemical models used is discussed.

National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:kth:diva-32248 (URN)10.1039/c0dt01490g (DOI)000288563100009 ()2-s2.0-79952850411 (Scopus ID)
Note
QC 20110524Available from: 2011-05-24 Created: 2011-04-11 Last updated: 2017-12-11Bibliographically approved
Szabo, Z. & Grenthe, I. (2010). On the Mechanism of Oxygen Exchange Between Uranyl(VI) Oxygen and Water in Strongly Alkaline Solution as Studied by O-17 NMR Magnetization Transfer. Inorganic Chemistry, 49(11), 4928-4933
Open this publication in new window or tab >>On the Mechanism of Oxygen Exchange Between Uranyl(VI) Oxygen and Water in Strongly Alkaline Solution as Studied by O-17 NMR Magnetization Transfer
2010 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 49, no 11, p. 4928-4933Article in journal (Refereed) Published
Abstract [en]

The mechanism, rate constant, and activation parameters for the exchange between uranyl(VI)) oxygen and water oxygen in tetramethyl ammonium hydroxide solution, TMA-OH, have been determined using O-17 NMR magnetization transfer technique. In the concentration range investigated, the predominant complex is UO2(OH)(4)(2-). The experimental rate equation, rate = k(ex)[TMA-OH](free)[U(VI)](2)(total) indicates that the exchange takes place via a binuclear complex or transition state with the stoichiometry [(UO2(OH)(4)(2-))(UO2(OH)(5)(3-)]. The rate-determining step most likely takes place between the axial "yl" oxygens and the equatorial hydroxides. The experimental Gibbs energy of activation, Delta G(double dagger) = 60.8 +/- 2.4 kJ/mol is in good agreement with the value, Delta A(double dagger) approximate to Delta G(double dagger) = 52.3 +/- 5.4 kJ/mol, found by Buhl and Schreckenbach in a recent Car-Parrinello molecular dynamics study, indicating that their proposed "shuttle" mechanism may be applicable also on the proposed binuclear transition state.

Keywords
COMPLEXES, DYNAMICS, URANIUM(VI), HYDROXIDE, FLUORIDE, BINARY, EXAFS, RATES
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-27584 (URN)10.1021/ic9025624 (DOI)000278110100035 ()2-s2.0-77953058608 (Scopus ID)
Note
QC 20101214Available from: 2010-12-14 Created: 2010-12-13 Last updated: 2017-12-11Bibliographically approved
Szabo, Z., Vallet, V. & Grenthe, I. (2010). Structure and dynamics of binary and ternary lanthanide(III) and actinide(III) tris[4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione] (TTA) complexes. Part 2, the structure and dynamics of binary and ternary complexes in the Y(III)/Eu(III) -TTA - tributylphosphate (TBP) system in chloroform as studied by NMR spectroscopy. Dalton Transactions, 39(45), 10944-10952
Open this publication in new window or tab >>Structure and dynamics of binary and ternary lanthanide(III) and actinide(III) tris[4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione] (TTA) complexes. Part 2, the structure and dynamics of binary and ternary complexes in the Y(III)/Eu(III) -TTA - tributylphosphate (TBP) system in chloroform as studied by NMR spectroscopy
2010 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 39, no 45, p. 10944-10952Article in journal (Refereed) Published
Abstract [en]

The stoichiometric reaction mechanisms, rate constants and activation parameters for inter-and intramolecular ligand exchange reactions in the binary Y/Eu(TTA)(3)(OH2)(2)-HTTA and the ternary Y/Eu(TTA)(3)(OH2)(2)-TBP systems have been studied in chloroform using H-1 and P-31 NMR methods. Most complexes contain coordinated water that is in very fast exchange with water in the chloroform solvent. The exchange reactions involving TTA/HTTA and TBP are also fast, but can be studied at lower temperature. The rate constant and activation parameters for the intramolecular exchange between two structure isomers in Y(TTA)(3)(OH2)(2) and Y(TTA)(3)(TBP)(OH2) were determined from the line-broadening of the methine protons in coordinated TTA. The rate equations for the intermolecular exchange between coordinated TTA and free HTTA in both complexes are consistent with a two-step mechanism where the first step is a fast complex formation of HTTA, followed by a rate determining step involving proton transfer from coordinated HTTA to TTA. The rate constants for both the interand intramolecular exchange reactions are significantly smaller in the TBP system. The same is true for the activation parameters in the Y(TTA)(3)(OH2)(2)-HTTA and the ternary Y/Eu(TTA)(3)(TBP)(OH2)-HTTA systems, which are Delta H-not equal = 71.8 +/- 2.8 kJ mol(-1), Delta S-not equal = 62.4 +/- 10.3 J mol(-1) K-1 and Delta H-not equal = 38.8 +/- 0.6 kJ mol(-1), Delta S-not equal = -93.0 +/- 3.3 J mol(-1) K-1, respectively. The large difference in the activation parameters does not seem to be related to a difference in mechanism as judged by the rate equation; this point will be discussed in a following communication. The rate and mechanism for the exchange between free and coordinated TBP follows a two-step mechanism, involving the formation of Y(TTA)(3)(TBP)(2).

Keywords
RESONANCE, IONS
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-27091 (URN)10.1039/c0dt00314j (DOI)000284066100017 ()2-s2.0-78149442088 (Scopus ID)
Note
QC 20101210Available from: 2010-12-10 Created: 2010-12-06 Last updated: 2017-12-11Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-7552-1076

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