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  • 1.
    Björkbacka, Åsa
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Yang, Miao
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Gasparrini, Claudia
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Leygraf, Christofer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Jonsson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Kinetics and mechanisms of reactions between H2O2 and copper and copper oxides2015In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 44, no 36, p. 16045-16051Article in journal (Refereed)
    Abstract [en]

    One of the main challenges for the nuclear power industry today is the disposal of spent nuclear fuel. One of the most developed methods for its long term storage is the Swedish KBS-3 concept where the spent fuel is sealed inside copper canisters and placed 500 meters down in the bedrock. Gamma radiation will penetrate the canisters and be absorbed by groundwater thereby creating oxidative radiolysis products such as hydrogen peroxide (H2O2) and hydroxyl radicals (HO[radical dot]). Both H2O2 and HO[radical dot] are able to initiate corrosion of the copper canisters. In this work the kinetics and mechanism of reactions between the stable radiolysis product, H2O2, and copper and copper oxides were studied. Also the dissolution of copper into solution after reaction with H2O2 was monitored by ICP-OES. The experiments show that both H2O2 and HO[radical dot] are present in the systems with copper and copper oxides. Nevertheless, these species do not appear to influence the dissolution of copper to the same extent as observed in recent studies in irradiated systems. This strongly suggests that aqueous radiolysis can only account for a very minor part of the observed radiation induced corrosion of copper.

  • 2. Buehl, Michael
    et al.
    Grenthe, Ingmar
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
    Binding modes of oxalate in UO(2)(oxalate) in aqueous solution studied with first-principles molecular dynamics simulations. Implications for the chelate effect2011In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 40, no 42, p. 11192-11199Article in journal (Refereed)
    Abstract [en]

    Car-Parrinello molecular dynamics simulations are reported for aqueous UO(2)(H(2)O)(n)(C(2)O(4)) (n = 3, 4), calling special attention to the binding modes of oxalate and the thermodynamics of the so-called chelate effect. Based on free energies from thermodynamic integration (BLYP functional), the kappa(1),kappa(1')-binding mode of the oxalate (with one O atom from each carboxylate coordinating) is more stable than kappa(2) (2 O atoms from the same carboxylate) and kappa(1) forms by 23 and 39 kJ mol(-1), respectively. The free energy of binding a fourth water ligand to UO(2)(H(2)O)(3)(kappa(1)-C(2)O(4)) is computed to be low, 12 kJ mol(-1). Changes of the hydration shell about oxalate during chelate opening are discussed. Composite enthalpies and free energies, obtained from both experiment and quantum-chemical modeling, are proposed for the formation of monodentate UO(2)(H(2)O)(4)(kappa(1)-C(2)O(4)). These data suggest that the largest entropy change in the overall complex formation occurs at this stage, and that the subsequent chelate closure under water release is essentially enthalpy-driven.

  • 3. Cheng, Minglun
    et al.
    Wang, Mei
    Zheng, Dehua
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Effect of the S-to-S bridge on the redox properties and H-2 activation performance of diiron complexes related to the [FeFe]-hydrogenase active site2016In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 45, no 44, p. 17687-17696Article in journal (Refereed)
    Abstract [en]

    Three biomimetic models of the [FeFe]-hydrogenase active site, namely diiron dithiolates of [(mu-edt){Fe(CO)(3)}{Fe(CO)(kappa(2)-PNP)}] (1, edt = ethane-1,2-dithiolate, PNP = Ph2PCH2N(nPr)CH2PPh2), [(mu bdtMe){Fe(CO)(3)}{Fe(CO)(kappa(2)-PNP)}] (2, bdtMe = 4-methylbenzene-1,2-dithiolate), and [(mu-adtBn){Fe(CO)(3)} {Fe(CO)(kappa(2)-PNP)}] (3, adtBn = N-benzyl-2-azapropane-1,3-dithiolate), were prepared and structurally characterized. These complexes feature the same PNP ligand but different S-to-S bridges. Influence of the S-to-S bridge on the electrochemical properties and chemical oxidation reactivity of 1-3 was studied by cyclic voltammetry and by in situ IR spectroscopy. The results reveal that the S-to-S bridge has a considerable effect on the oxidation reactivity of 1-3 and on the stability of in situ generated single-electron oxidized complexes, [1](+), [2](+), and [3](+). The performances of [1](+) and [2](+) for H-2 activation were explored in the presence of a mild chemical oxidant, while rapid decomposition of [3](+) thwarted the further study of this complex. Gratifyingly, 1 was found to be catalytically active, although in a low turnover number, for H-2 oxidation in the presence of excess mild oxidant and a proton trapper under 1 atm H-2 at room temperature.

  • 4.
    Daniel, Quentin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Wang, Lei
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Duan, Lele
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Li, Fusheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. Dalian Univ Technol, Peoples R China.
    Tailored design of ruthenium molecular catalysts with 2,2 '-bypyridine-6,6 '-dicarboxylate and pyrazole based ligands for water oxidation2016In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 45, no 37, p. 14689-14696Article in journal (Refereed)
    Abstract [en]

    With the incorporation of pyrazole and DMSO as axial ligands, a series of tailor-designed Ru water oxidation catalysts [Ru(bda)(DMSO)(L)] (H(2)bda = 2,2'-bypyridine-6,6'-dicarboxylic acid; DMSO = dimethyl sulfoxide; L = pyrazole, A-1; 4-Br-3-methyl pyrazole, B-1) and [Ru(bda)(L)(2)] (L = pyrazole, A-2; 4-Br-3-methyl pyrazole, B-2) have been generated in situ from their corresponding precursors [Ru(kappa(O,N,N)(3)-bda) (DMSO)(x)(L)(3-x)] which are in a zwitterionic form with an extra pyrazole based ligand in the equatorial position. Formation of the active catalyst has been investigated under pH 1.0 conditions. Electrochemistry and water oxidation activity of these catalysts were investigated. By fine tuning of the catalyst structure, the turnover frequency was increased up to 500 s(-1) and the stability over 6000 turnovers.

  • 5.
    Diesen, Veronica
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Dunnill, Charles W.
    Österberg, Elin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Parkin, Ivan Paul
    Jonsson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Silver enhanced TiO2 thin films: photocatalytic characterization using aqueous solutions of tris(hydroxymethyl)aminomethane2014In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 43, no 1, p. 344-351Article in journal (Refereed)
    Abstract [en]

    The photocatalytic activity in aqueous solutions of TiO2 and Ag enhanced TiO2 sol-gel produced films was characterized using tris(hydroxymethyl)aminomethane (Tris) under black light (365 nm) and the observed differences in efficiency were further investigated by O-2 adsorption studies using the same probe. Hydrogen abstracting species, such as hydroxyl radicals formed upon photocatalysis, are able to abstract hydrogen from Tris. This reaction leads to the formation of formaldehyde which was detected and quantified through a modified version of the Hantzsch reaction. It was found that the Ag enhanced TiO2 film increased the apparent quantum yield from 7% to 12%, partly as a result of a Schottky barrier formation at the metal-semiconductor interface and partly as the sensitizing effect of Ag nanoparticles extends the visible light absorption, which through electron transfer processes enable an efficient charge separation in the TiO2 by attracting acceptor species more efficiently than pure TiO2. The O-2 adsorption studies in this paper showed that the Ag enhanced TiO2 film has a stronger adsorption affinity than pure TiO2 towards O-2, which make the reduction of O-2 more efficient with a subsequent enhanced electron-hole lifetime. It was also found that the Ag enhanced TiO2 film had a poorer adsorption affinity for Tris than the pure TiO2 film, which is a consequence of fewer available surface adsorption sites due to the Ag coverage at 64% which agrees well with the obtained adsorption equilibrium constants (K-LH(TiO2) = 615 M-1 and KLH(Ag-TiO2) = 320 M-1).

  • 6. Ekström, Jesper
    et al.
    Abrahamsson, Maria
    Olson, Carol
    Bergquist, Jonas
    Kaynak, Filiz B.
    Eriksson, Lars
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Becker, Hans-Christian
    Akermark, Bjoern
    Hammarstroem, Leif
    Ott, Sascha
    Bio-inspired, side-on attachment of a ruthenium photosensitizer to an iron hydrogenase active site model2006In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, no 38, p. 4599-4606Article in journal (Refereed)
    Abstract [en]

    The first ruthenium - diiron complex [(mu- pdt) Fe-2(CO)(5){PPh2(C(6)H(4)CCbpy)} Ru(bpy)(2)](2+) 1 (pdt = propyldithiolate, bpy = 2,2'-bipyridine) is described in which the photoactive ruthenium trisbipyridyl unit is linked to a model of the iron hydrogenase active site by a ligand directly attached to one of the iron centers. Electrochemical and photophysical studies show that the light-induced MLCT excited state of the title complex is localized towards the potential diiron acceptor unit. However, the relatively mild potential required for the reduction of the acetylenic bipyridine together with the easily oxidized diiron portion leads to a reductive quenching of the excited state, instead. This process results in a transiently oxidized diiron unit which may explain the surprisingly high light sensitivity of complex 1.

  • 7.
    Farnum, Byron H.
    et al.
    Johns Hopkins University.
    Gardner, James M.
    Johns Hopkins University.
    Marton, Andras
    Johns Hopkins University.
    Narducci-Sarjeant, Amy A.
    Johns Hopkins University.
    Meyer, Gerald J.
    Johns Hopkins University.
    Influence of ion pairing on the oxidation of iodide by MLCT excited states2011In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 40, no 15, p. 3830-3838Article in journal (Refereed)
    Abstract [en]

    The oxidation of iodide to diiodide, I2[radical dot]-, by the metal-to-ligand charge-transfer (MLCT) excited state of [Ru(deeb)3]2+, where deeb is 4,4[prime or minute]-(CO2CH2CH3)2-2,2[prime or minute]-bipyridine, was quantified in acetonitrile and dichloromethane solution at room temperature. The redox and excited state properties of [Ru(deeb)3]2+ were similar in the two solvents; however, the mechanisms for excited state quenching by iodide were found to differ significantly. In acetonitrile, reaction of [Ru(deeb)3]2+* and iodide was dynamic (lifetime quenching) with kinetics that followed the Stern-Volmer model (KD = 1.0 +/- 0.01 [times] 105 M-1, kq = 4.8 [times] 1010 M-1 s-1). Excited state reactivity was observed to be the result of reductive quenching that yielded the reduced ruthenium compound, [Ru(deeb-)(deeb)2]+, and the iodine atom, I[radical dot]. In dichloromethane, excited state quenching was primarily static (photoluminescence amplitude quenching) and [Ru(deeb-)(deeb)2]+ formed within 10 ns, consistent with the formation of ion pairs in the ground state that react rapidly upon visible light absorption. In both solvents the appearance of I2[radical dot]- could be time resolved. In acetonitrile, the rate constant for I2[radical dot]- growth, 2.2 +/- 0.2 [times] 1010 M-1 s-1, was found to be about a factor of two slower than the formation of [Ru(deeb-)(deeb)2]+, indicating it was a secondary photoproduct. The delayed appearance of I2[radical dot]- was attributed to the reaction of iodine atoms with iodide. In dichloromethane, the growth of I2[radical dot]-, 1.3 +/- 0.4 [times] 1010 M-1 s-1, was similar to that in acetonitrile, yet resulted from iodine atoms formed within the laser pulse. These results are discussed within the context of solar energy conversion by dye-sensitized solar cells and storage via chemical bond formation.

  • 8.
    Freys, Jonathan C.
    et al.
    Uppsala University.
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    D'Amario, Luca
    Uppsala University.
    Brown, Allison M.
    Uppsala University.
    Hammarström, Leif
    Uppsala University.
    Ru-based donor-acceptor photosensitizer that retards charge recombination in a p-type dye-sensitized solar cell2012In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 41, no 42, p. 13105-13111Article in journal (Refereed)
    Abstract [en]

    We report on the synthesis and characterization of a donor-acceptor ruthenium polypyridyl complex as a photosensitizer for p-type dye-sensitized solar cells (DSSCs). The electrochemical, photophysical, and photovoltaic performance of two ruthenium-based photosensitizers were tested in NiO-based DSSCs; bis-(2,2'-bipyridine-4,4'-dicarboxylic acid)(2)N-(1,10-phenanthroline)-4-nitronaphthalene-1,8-dicarboximide ruthenium(ii), ([Ru(dcb)(2)(NMI-phen)](PF(6))(2)) and tris-(2,2'-bipyridine-4,4'-dicarboxylic acid)(3) ruthenium(ii), [(Ru(dcb)(3))Cl(2)]. The presence of an electron-accepting group, 4-nitronaphthalene-1,8-dicarboximide (NMI), attached to the phenanthroline of [Ru(dcb)(2)(NMI-phen)](2+) resulted in long-lived charge separation between reduced [Ru(dcb)(2)(NMI-phen)](2+) and NiO valence band holes; 10-50 μs. In the reduced state for [Ru(dcb)(2)(NMI-phen)](2+), the electron localized on the distal NMI group. In tests with I(3)(-)/I(-) and Co(4,4'-di-tert-butyl-bipyridine)(3)(2+/3+) electrolytes, [Ru(dcb)(2)(NMI-phen)](2+) outperformed [Ru(dcb)(3)](2+) in solar cell efficiency in devices. A record APCE (25%) was achieved for a ruthenium photosensitizer in a p-type DSSC. Insights on photosensitizer regeneration kinetics are included.

  • 9. García-Gallego, Sandra
    et al.
    Cangiotti, Michela
    Fiorani, Luigi
    Fattori, Alberto
    Muñoz-Fernández, Ma Ángeles
    Gomez, Rafael
    Ottaviani, M Francesca
    de la Mata, F Javier
    Anionic sulfonated and carboxylated PPI dendrimers with the EDA core: synthesis and characterization of selective metal complexing agents.2013In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 42, no 16, p. 5874-89Article in journal (Refereed)
    Abstract [en]

    Herein we describe the synthesis and characterization of new sulfonated and carboxylated poly(propyleneimino) (PPI) dendrimers with the ethylenediamino (EDA) core, at generations 1, 2 and 3. By means of UV-Vis and EPR spectroscopy, using Cu(2+) as a probe, we concluded that these dendrimers show a specific pattern in the coordination of metal ions. In agreement with the UV-Vis studies, EPR spectra of carboxylated compounds are constituted by 3 different signals which appear and then disappear with increasing copper concentration, corresponding to the saturation of different copper complexation sites. At the lowest copper concentration up to a 1:1 molar ratio between Cu(II) and the dendrimer, the spectrum is characteristic of a CuN2O2 coordination at the core of the dendrimer. The spectrum appearing at higher Cu(II) concentrations indicates a peripheral location of the ions coordinating one nitrogen and 3 oxygen atoms in a square planar geometry in restricted mobility conditions. For the highest concentrations tested, copper ions are confined at the external dendrimer surface with CuO4 coordination. For sulfonate systems, the EPR results are in line with a weaker interaction of Cu(II) with the nitrogen sites and a stronger interaction with the oxygen (SO3(-)) groups with respect to the interactions measured by EPR for carboxylate systems.

  • 10. García-Gallego, Sandra
    et al.
    Rodríguez, Javier Sánchez
    Jiménez, José Luis
    Cangiotti, Michela
    Ottaviani, Maria Francesca
    Muñoz-Fernández, M Ángeles
    Gómez, Rafael
    de la Mata, F Javier
    Polyanionic N-donor ligands as chelating agents in transition metal complexes: synthesis, structural characterization and antiviral properties against HIV2012In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 41, no 21, p. 6488-99Article in journal (Refereed)
    Abstract [en]

    We describe here the synthesis and characterization of new sulfonated and carboxylated-containing N-donor ligands [Na(4)(edts)]·4H(2)O (2), [Na(2)(dmeddp)]·2H(2)O (3) and [Na(4)(edtp)]·H(2)O (4) (edts = ethylene-diamine- N,N,N',N'-tetraethylenesulfonate ion; dmeddp = dimethyl-ethylene-diamine-N,N,N',N'-tetra-3-propionate ion; edtp = ethylene-diamine-N,N,N',N'-tetra-3-propionate ion) and their corresponding metal (Ni, Co, Cu and Zn) complexes. Mainly, UV-Vis and a computer aided analysis of the EPR spectra provided information on the geometry and structure of the complexes in solution. Some of the metal complexes inhibit HIV replication when treating both pre- and post-infected PBMC cells, and hustle the inhibitory effect compared to the metal salts alone.

  • 11.
    Gorlov, Mikhail
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry (closed 20110630).
    Kloo, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry (closed 20110630).
    Ionic liquid electrolytes for dye-sensitized solar cells2008In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, no 20, p. 2655-2666Article in journal (Refereed)
    Abstract [en]

    The potential of room-temperature molten salts (ionic liquids) as solvents for electrolytes for dye-sensitized solar cells has been investigated during the last decade. The non-volatility, good solvent properties and high electrochemical stability of ionic liquids make them attractive solvents in contrast to volatile organic solvents. Despite this, the relatively high viscosity of ionic liquids leads to mass-transport limitations. Here we review recent developments in the application of different ionic liquids as solvents or components of liquid and quasi-solid electrolytes for dye-sensitized solar cells.

  • 12. Hao, Yan
    et al.
    Wood, Christopher J.
    Clark, Charlotte A.
    Calladine, James A.
    Horvath, Raphael
    Hanson-Heine, Magnus W. D.
    Sun, Xue-Zhong
    Clark, Ian P.
    Towrie, Michael
    George, Michael W.
    Yang, Xichuan
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Gibson, Elizabeth A.
    Can aliphatic anchoring groups be utilised with dyes for p-type dye sensitized solar cells?2016In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 45, no 18, p. 7708-7719Article in journal (Refereed)
    Abstract [en]

    A series of novel laterally anchoring tetrahydroquinoline derivatives have been synthesized and investigated for their use in NiO-based p-type dye-sensitized solar cells. The kinetics of charge injection and recombination at the NiO-dye interface for these dyes have been thoroughly investigated using pico-second transient absorption and time-resolved infrared measurements. It was revealed that despite the anchoring unit being electronically decoupled from the dye structure, charge injection occurred on a sub picosecond timescale. However, rapid recombination was also observed due to the close proximity of the electron acceptor on the dyes to the NiO surface, ultimately limiting the performance of the p-DSCs.

  • 13.
    Horne, Gregory P.
    et al.
    Idaho Natl Lab, Ctr Radiat Chem Res, POB 1625, Idaho Falls, ID 83415 USA..
    Zarzana, Christopher A.
    Idaho Natl Lab, Ctr Radiat Chem Res, POB 1625, Idaho Falls, ID 83415 USA..
    Grimes, Travis S.
    Idaho Natl Lab, Ctr Radiat Chem Res, POB 1625, Idaho Falls, ID 83415 USA..
    Rae, Cathy
    Idaho Natl Lab, Ctr Radiat Chem Res, POB 1625, Idaho Falls, ID 83415 USA..
    Ceder, Joakim
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Chemical Engineering. Idaho Natl Lab, Ctr Radiat Chem Res, POB 1625, Idaho Falls, ID 83415 USA..
    Mezyk, Stephen P.
    Calif State Univ Long Beach, Dept Chem & Biochem, Long Beach, CA 90804 USA..
    Mincher, Bruce J.
    Idaho Natl Lab, Ctr Radiat Chem Res, POB 1625, Idaho Falls, ID 83415 USA..
    Charbonnel, Marie-Christine
    Univ Montpellier, CEA, DEN, DMRC, Marcoule, France..
    Guilbaud, Philippe
    Univ Montpellier, CEA, DEN, DMRC, Marcoule, France..
    Saint-Louis, George
    Univ Montpellier, CEA, DEN, DMRC, Marcoule, France..
    Berthon, Laurence
    Univ Montpellier, CEA, DEN, DMRC, Marcoule, France..
    Effect of chemical environment on the radiation chemistry of N,N-di-(2-ethylhexyl)butyramide (DEHBA) and plutonium retention2019In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 48, no 38, p. 14450-14460Article in journal (Refereed)
    Abstract [en]

    N,N-di-(2-ethylhexyl)butyramide (DEHBA) has been proposed as part of a hydro-reprocessing solvent extraction system for the co-extraction of uranium and plutonium from spent nuclear fuel, owing to its selectivity for hexavalent uranium and tetravalent plutonium. However, there is a critical lack of quantitative understanding regarding the impact of chemical environment on the radiation chemistry of DEHBA, and how this would affect process performance. Here we present a systematic investigation into the radiolytic degradation of DEHBA in a range of n-dodecane solvent system formulations, where we subject DEHBA to gamma irradiation, measure reaction kinetics, ligand integrity, degradation product formation, and investigate solvent system performance through uranium and plutonium extraction and strip distribution ratios. The rate of DEHBA degradation in n-dodecane was found to be slow (G = -0.31 +/- 0.02 mu mol J(-1)) but enhanced upon contact with the oxidizing conditions of the investigated solvent systems (organic-only, or in contact with either 0.1 or 3.0 M aqueous nitric acid). Two major degradation products were identified in the organic phase, bis-2-ethylhexylamine (b2EHA) and N-(2-ethylhexyl)butyramide (MEHBA), resulting from the cleavage of C-N bonds, and could account for the total loss of DEHBA up to similar to 300 kGy for organic-only conditions. Both b2EHA and MEHBA were also found to be susceptible to radiolytic degradation, having G-values of -0.12 +/- 0.01 and -0.08 +/- 0.01 mu mol J(-1), respectively. Solvent extraction studies showed: (i) negligible change in uranium extraction and stripping with increasing absorbed dose; and (ii) plutonium extraction and retention exhibits complex dependencies on absorbed dose and chemical environment. Organic-only conditions afforded enhanced plutonium extraction and retention attributed to b2EHA, while acid contacts inhibited this effect and promoted significant plutonium retention for the highest acidity. Overall it has been demonstrated that chemical environment during irradiation has a significant influence on the extent of DEHBA degradation and plutonium retention.

  • 14. Hu, Minggang
    et al.
    Wang, Mei
    Zhu, Hongjun
    Zhang, Lu
    Zhang, Hui
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Preparation and structures of enantiomeric dinuclear zirconium and hafnium complexes containing two homochiral N atoms, and their catalytic property for polymerization of rac-lactide2010In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 39, no 18, p. 4440-4446Article in journal (Refereed)
    Abstract [en]

    The hydroxy-and phenoxy-bridged dinuclear zirconium and hafnium complexes 2 and 3 of an amine-pyridine-bis(phenolate) ligand (H2L) were prepared from the reaction of Na2L and ZrCl4 in the presence of 0.5 equiv of water in THF, while the reaction of H2L with NaH and then with ZrCl4 in the freshly distilled THF gave an eight-coordinate bis(homoleptic) mononuclear complex L2Zr (1). Two homochiral N atoms were created in each complex upon coordination of the unsymmetric tertiary amine ligands to the metal centers. Enantiomeric dinuclear complexes 2 and 3 both undergo spontaneous resolution during crystallization. The molecular structure of each enantiomer of 2 and 3, as well as the structure of 1, was determined by X-ray analysis and the circular dichroism spectra of N(R)N(R)-2 and N(S)N(S)-2 were studied. The racemates of 2 and 3 catalyzed controlled polymerization of rac-lactide in terms of the linearity of molecular weight versus conversion, forming isotactic-rich polylactide in high yields with a narrow polydispersity.

  • 15.
    Hutchinson, Daniel J.
    et al.
    Institut für Anorganische Chemie, Universität Leipzig.
    Clauss, R.
    Institut für Anorganische Chemie, Universität Leipzig.
    Sarosi, M. B.
    Institut für Anorganische Chemie, Universität Leipzig.
    Hey-Hawkins, Evamarie
    Institut für Anorganische Chemie, Universität Leipzig.
    Supramolecular self-assembly of heterobimetallic complexes: a new N,P-based, selective heteroditopic ligand2018In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 47, no 4, p. 1053-1061Article in journal (Refereed)
    Abstract [en]

    Pyrimidine-hydrazone and phosphole architectures have been combined to create a new heteroditopic ligand capable of forming heterobimetallic Zn(II)/Pd(II), Pb(II)/Pd(II) and Cu(II)/Pd(II) complexes in high yielding stepwise or one pot reactions. The catalytic activity of these complexes in Heck coupling and Miyaura borylation reactions was investigated.

  • 16.
    Hutchinson, Daniel J.
    et al.
    Department of Chemistry, University of Otago.
    Hanton, Lyall R.
    Department of Chemistry, University of Otago.
    Moratti, S. C.
    Tetratopic pyrimidine-hydrazone ligands modified with terminal hydroxymethyl and acryloyl arms and their Pb(II), Zn(II), Cu(II) and Ag(I) complexes2014In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 43, no 22, p. 8205-18Article in journal (Refereed)
    Abstract [en]

    The first tetratopic pyrimidine-hydrazone (pym-hyz) molecular strands containing terminal hydroxymethyl (L1) and acryloyl (L2) functional groups have been synthesised. L1 was produced by step-wise imine condensation reactions, starting with 6-hydroxymethyl-2-pyridinecarboxaldehyde. L2 was then synthesised through the treatment of L1 with acryloyl chloride. NMR spectroscopy and X-ray crystallography showed that the ligands adopted a helical shape, comprised of 1 and 1/3 helical turns. Both L1 and L2 uncoiled upon reaction with an excess amount of Pb(II), Zn(II) and Cu(II) ions, resulting in linear M4LA8 complexes (where M = Pb(II), Zn(II), or Cu(II); L = L1 or L2; and A = ClO4(-), SO3CF3(-) or BF4(-)). Horse-shoe shaped Pb2LA4 complexes were also formed by reacting Pb(II) ions with either L1 or L2 in a 2 : 1 metal to ligand ratio. The addition of Ag(I) ions to either L1 or L2 resulted in Ag2L2A2 double helicates, which were stable in the presence of excess Ag(I). The Pb(II), Zn(II) and Ag(I) complexes were characterised by NMR spectroscopy, while UV-Vis spectroscopy was used to probe the Cu(II) complexes. In addition, X-ray crystallography was used to analyse the linear Pb4L1A8, horse-shoe shaped Pb2L1(ClO4)4, twisted Cu3L2(SO3CF3)6, and double helicate Ag2L12(SO3CF3)2 complexes yielding the structures [Pb4L1(ClO4)7(H2O)]ClO4.4CH3NO2 (1), [Pb4L1(SO3CF3)8]2.6CH3CN.H2O (2), [Pb2L1(ClO4)2(CH3CN)(H2O)](ClO4)2.2CH3CN.C4H10O.H2O (3), [Cu3L2(SO3CF3)3(CH3CN)2(H2O)](SO3CF3)3.2CH3CN.H2O (4) and [Ag2L12](SO3CF3)2.CH3CN.H2O (5), respectively.

  • 17. Jiang, Shi
    et al.
    Liu, Jianhui
    Shi, Yu
    Wang, Zhen
    Akermark, Bjorn
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Fe-S complexes containing five-membered heterocycles: novel models for the active site of hydrogenases with unusual low reduction potential2007In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, no 8, p. 896-902Article in journal (Refereed)
    Abstract [en]

    Three biomimetic 2Fe2S complexes [{(mu-SCH2)(2)NCH2(2-C4H3O)}](Fe-2(CO)(6)) (6a), [{(mu-SCH2)(2) NCH2(2-C4H3S)}](Fe-2(CO)(6)) (6b) and [{(mu-SCH2)(2)NCH2(5-Br-2-C4H2S)}Fe-2(CO)(6)] (6c) were prepared as models for the active site of Fe-only hydrogenase by the convergent process from [(mu-S-2)Fe-2(CO)(6)] and N,N-bis(hydromethyl)-2-furan and thiophene. The structures of these complexes were identified spectroscopically and crystallographically. The electrochemical behavior of the complexes 6a and 6c was unique as they showed catalytic proton reduction with a low reduction potential at -1.13 and -1.09 V vs Fc/Fc(+), respectively, in the presence of HClO4.

  • 18.
    Johansson, Adam Johannes
    et al.
    Stockholm Univ, Dept Phys.
    Noack, Holger
    Siegbahn, Per E. M.
    Xue, Genqiang
    Que, Lawrence, Jr.
    Observed enhancement of the reactivity of a biomimetic diiron complex by the addition of water - mechanistic insights from theoretical modeling2009In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, no 34, p. 6741-6750Article in journal (Refereed)
    Abstract [en]

    The biomimetic diiron complex [Fe(III)Fe(IV)(mu-O)(2)(5-Me(3)-TPA)(2)](ClO(4))(3) (TPA = tris(2-pyridylmethyl) amine) has been found to be capable of oxidizing 9,10-dihydroanthracene in a solution of acetonitrile. Addition of water up to 1 M makes the reaction 200 times faster, suggesting that the water molecule in some way activates the catalyst for more efficient substrate oxidation. It is proposed that the enhanced reactivity results from the coordination of a water molecule to the iron(III) half of the complex, converting the bis-mu-oxo structure of the diiron complex to a ring-opened form where one of the bridging oxo groups is transformed into a terminal oxo group on iron(IV). The suggested mechanism is supported by DFT (B3LYP) calculations and transition state theory. Two different computational models of the diiron complex are used to model the hydroxylation of cyclohexane to cyclohexanol. Model 1 has a bis-mu-oxo diiron core (diamond core) while model 2 represents the "open core" analogue with one bridging mu-oxo group, a terminal oxo ligand on iron(IV), and a water molecule coordinated to iron(III). The computational results clearly suggest that the terminal oxo group is more reactive than the bridging oxo group. The free energy of activation is 7.0 kcal mol(-1) lower for the rate limiting step when the oxidant has a terminal oxo group than when both oxo groups are bridging the irons.

  • 19. Johnson, Magnus T.
    et al.
    Dzolic, Zoran
    Cetina, Mario
    Lahtinen, Manu
    Ahlquist, Marten S. G.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Rissanen, Kari
    Ohrstrom, Lars
    Wendt, Ola F.
    Preparation of potentially porous, chiral organometallic materials through spontaneous resolution of pincer palladium conformers2013In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 42, no 23, p. 8484-8491Article in journal (Refereed)
    Abstract [en]

    Understanding the mechanism by which advanced materials assemble is essential for the design of new materials with desired properties. Here, we report a method to form chiral, potentially porous materials through spontaneous resolution of conformers of a PCP pincer palladium complex ({2,6-bis[(di-t-butyl-phosphino)methyl]phenyl}palladium(II)halide). The crystallisation is controlled by weak hydrogen bonding giving rise to chiral qtz-nets and channel structures, as shown by 16 such crystal structures for X = Cl and Br with various solvents like pentane and bromobutane. The fourth ligand (in addition to the pincer ligand) on palladium plays a crucial role; the chloride and the bromide primarily form hexagonal crystals with large 1D channels, whereas the iodide (presumably due to its inferior hydrogen bonding capacity) forms monoclinic crystals without channels. The hexagonal channels are completely hydrophobic and filled with disordered solvent molecules. Upon heating, loss of the solvent occurs and the hexagonal crystals transform into other non-porous polymorphs. Also by introducing a strong acid, the crystallisation process can be directed to a different course, giving several different non-porous polymorphs. In conclusion, a number of rules can be formulated dictating the formation of hexagonal channel structures based on pincer palladium complexes. Such rules are important for a rational design of future self-assembling materials with applications in storage and molecular recognition.

  • 20.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Inorganic chemistry for renewable energy conversion and storage2014In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 43, no 40, p. 14924-14925Article in journal (Refereed)
  • 21. Lele, Duan
    et al.
    Mei, Wang
    Ping, Li
    Yong, Na
    Ning, Wang
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Carbene-pyridine chelating 2Fe2S hydrogenase model complexes as highly active catalysts for the electrochemical reduction of protons from weak acid (HOAc)2007In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, no 13, p. 1277-1283Article in journal (Refereed)
    Abstract [en]

    Two asymmetrically disubstituted diiron complexes (mu-pdt)[Fe(CO)(3)][Fe(CO)(eta(2)-L)] (L = 1-methyl-3-(2-pyridyl)imidazol-2-ylidene (NHCMePy), 2; 1,3-bis(2-picolyl) imidazol-2-ylidene (NHCdiPic), 4) and a mono-substituted diiron complex (mu-pdt)[Fe(CO)(3)][Fe(CO)(2)(NHCdiPic)] (3) were prepared as biomimetic models of the Fe-only hydrogenase active site. X-Ray studies show that the NHCMePy and NHCdiPic ligands in 2 and 4 each coordinate to the single iron atom as NHC-Py chelating ligands in two basal positions and the NHCdiPic ligand of complex 3 lies in an apical position as a monodentate ligand. The large ranges of the highest and the lowest nu(CO) frequencies of 2 and 4 reflect that the relatively uneven electron density on the two iron atoms of the 2Fe2S model complexes 2 and 4 is as that observed for mono-substituted diiron complexes of good donor ligands. The cyclic voltammograms and the electrochemical proton reduction by 2 and 3 were studied in the presence of HOAc to evaluate the effect of asymmetrical substitution of strong donor ligands on the redox properties of the iron atoms and on the electrocatalytic activity for proton reduction.

  • 22.
    Li, Deyang
    et al.
    Harbin Inst Technol, Sch Chem & Chem Engn, MIIT Key Lab Crit Mat Technol New Energy Convers, Harbin 150001, Heilongjiang, Peoples R China.;Harbin Inst Technol, Minist Educ, Key Lab Microsyst & Microstruct, Harbin 150001, Heilongjiang, Peoples R China..
    Ågren, Hans
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology. Harbin Inst Technol, Sch Chem & Chem Engn, MIIT Key Lab Crit Mat Technol New Energy Convers, Harbin 150001, Heilongjiang, Peoples R China.;Harbin Inst Technol, Minist Educ, Key Lab Microsyst & Microstruct, Harbin 150001, Heilongjiang, Peoples R China.
    Chen, Guanying
    Harbin Inst Technol, Sch Chem & Chem Engn, MIIT Key Lab Crit Mat Technol New Energy Convers, Harbin 150001, Heilongjiang, Peoples R China.;Harbin Inst Technol, Minist Educ, Key Lab Microsyst & Microstruct, Harbin 150001, Heilongjiang, Peoples R China..
    Near infrared harvesting dye-sensitized solar cells enabled by rare-earth upconversion materials2018In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 47, no 26, p. 8526-8537Article, review/survey (Refereed)
    Abstract [en]

    Dye-sensitized solar cells (DSSCs) have been deemed as promising alternatives to silicon solar cells for the conversion of clean sunlight energy into electricity. A major limitation to their conversion efficiency is their inability to utilize light in the infrared (IR) spectral range, which constitutes almost half the energy of the sun's radiation. This fact has elicited motivations and endeavors to extend the response wavelength of DSSCs to the IR range. Photon upconversion through rare-earth ions constitutes one of the most promising approaches toward the goal of converting near-IR (NIR) or IR light into visible or ultraviolet light, where DSSCs typically have high sensitivity. In the present review, we summarize recent progress based on the utilization of various upconversion materials and device structures to improve the performance of dye-sensitized solar cells.

  • 23. Li, F.
    et al.
    Wang, M.
    Ma, C. B.
    Gao, A. P.
    Chen, H. B.
    Sun, Licheng C.
    Mono- and binuclear complexes of iron(II) and iron(III) with an N4O ligand: synthesis, structures and catalytic properties in alkane oxidation2006In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, no 20, p. 2427-2434Article in journal (Refereed)
    Abstract [en]

    Three mononuclear iron complexes and one binuclear iron complex, [Fe(tpoen)Cl]center dot 0.5(Fe2OCl6) (1), [Fe(tpoen)Cl]PF6 (2), Fe(tpoen)Cl-3 (3) and [{Fe(tpoen)}(2)(mu-O)](ClO4)(4) (4) (tpoen = N-(2-pyridylmethoxyethyl)-N,N-bis(2-pyridylmethyl)amine), were synthesized as functional models of non-heme iron oxygenases. Crystallographic studies revealed that the Fe(II) center of 1 is in a pseudooctahedral environment with a pentadentate N4O ligand and a chloride ion trans to the oxygen atom. The Fe(III) center of 3 is ligated by three nitrogen atoms of tpoen and three chloride ions in a facial configuration. Each Fe(III) center of 4 is coordinated with four nitrogen atoms and an oxygen atom of tpoen with the Fe-O-Fe angle of 172.0(3) angstrom. Complexes 2, 3 and 4 catalysed the oxidation of cyclohexane with H2O2 in the total TNs of 24 - 36 with A/K ratios of 1.9-2.4. Under the same conditions they also catalysed both the oxidation of ethylbenzene to benzylic alcohol and acetobenzene with good activity (30-47 TN) and low selectivity (A/K 0.7), and the oxidation of adamantane with moderate activity (15-18 TN) and low regioselectivity (3 degrees/2 degrees 3.0-3.2). With mCPBA as oxidant the catalytic activities of 2, 3 and 4 increased 1.8 to 2.3-fold for the oxidation of cyclohexane and ethylbenzene and 6.3 to 7.5-fold for the oxidation of adamantane. Drastic enhancement of the regioselectivity was observed in the oxidation of adamantane (3 degrees/2 degrees 18.5-30.3).

  • 24. Li, Ping
    et al.
    Wang, Mei
    Chen, Lin
    Liu, Jihong
    Zhaoa, Zhenbo
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Structures, protonation, and electrochemical properties of diiron dithiolate complexes containing pyridyl-phosphine ligands2009In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, no 11, p. 1919-1926Article in journal (Refereed)
    Abstract [en]

    Diiron complexes containing pyridyl-phosphine ligands, that is, (mu-pdt)[Fe-2(CO)(5)L] (pdt = S(CH2)(3)S, L = Ph2PCH2Py, 3a; Ph2PPy, 3b) and (mu-pdt)[Fe(CO)(2)(PMe3)][Fe(CO)(2)L] (L = Ph2PCH2Py, 4a; Ph2PPy, 4b) were prepared as model complexes of the [FeFe]-hydrogenase active site. Protonation of 3a and 3b by HOTf afforded the pyridyl-nitrogen protonated products [3aH(N)][OTf] and [3bH(N)][OTf], respectively. The molecular structures of 3a, 3b, 4a, 4b, as well as [3aH(N)][OTf] and [3bH(N)][OTf] were confirmed by X-ray diffraction studies, which show that the Ph2PCH2Py ligand occupies the basal position both in 3a and its protonated species [3aH(N)][OTf], while the Ph2PPy ligand prefers the apical position in 3b and [3bH(N)][OTf]. The double protonation process of complex 4b was monitored by in situ IR, H-1 and P-31 NMR spectroscopy at low temperature. The spectroscopic evidence indicates that the protonation of 4b occurs first at the Fe-Fe bond and then at the pyridyl-nitrogen atom. Cyclic voltammograms reveal that protonation of 3a and 3b results in a considerable decrease in the overpotential for electrocatalytic proton reduction in the presence of HOTf, while the efficiency is not influenced by protonation. The electrocatalytic efficiency of 4a for proton reduction in the presence of HOAc in CH3CN-H2O (50:1, v/v) is 5 times higher than that in pure CH3CN.

  • 25.
    Li, Yunguo
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Korzhavyi, Pavel A.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Physical and chemical properties of Cu(I) compounds with O and/or H2017In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 46, no 2, p. 529-538Article in journal (Refereed)
    Abstract [en]

    The electronic structure and chemical bonding of Cu(I) compounds with O and/or H are investigated using ab initio calculations based on density functional theory. A hybrid functional PBE0 is employed, which accurately reproduces an experimental band gap of cuprite Cu2O. Cuprous hydroxide CuOH (cuprice) is found to be an indirect band gap semiconductor. Depending on the bond network configuration of CuOH, its band gap is found to vary between 2.73 eV and 3.03 eV. The presence of hydrogen in CuOH has little effect on the character of Cu-O bonds, as compared to Cu2O, but lowers the energy levels of the occupied states upon O- H bond formation. The bonding charge density and electron localization function calculations reveal that a closed-shell Cu-Cu interaction takes place in Cu2O and CuOH between the neighbouring Cu cations belonging to different bond networks. Besides, three structures of cuprous hydride CuH are investigated. We find that the halite structure of CuH can be stabilized at high pressure (above 32 GPa) while wurtzite is the most stable structure of CuH at ambient pressure. The H-H interaction contributes to the dynamical stabilization of the halite structure. The wurtzite and sphalerite structures of CuH are predicted to be semiconducting with small band gaps, while the halite structure is calculated to be metallic.

  • 26.
    Li, Zhuofeng
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Soroka, Inna
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Min, Fanyi
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Jonsson, Mats
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    pH-Control as a way to fine-tune the Cu/Cu2O ratio in radiation induced synthesis of Cu2O particles2018In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 47, no 45, p. 16139-16144Article in journal (Refereed)
    Abstract [en]

    In this work we have optimized the -radiation induced synthesis of Cu-Cu2O particles from aqueous CuSO4 solution by investigating the effect of pH. The obtained precipitate was analyzed by XRD and SEM techniques. The results indicated that at solution pH lower than 3.75, quasi-spherical Cu agglomerates can be formed while at pH higher than 4.40 only octahedron-shaped Cu2O particles are produced. At solution pH in the range from 3.75 to 4.40, a Cu-Cu2O mixture is produced. It was found that the relative amount of Cu2O in the Cu-Cu2O precipitate increases with pH in the studied range. The influence of solution pH on the Cu/Cu2O ratios in the product can be explained on the basis of pH-dependent competition kinetics between the reactions leading to either Cu or Cu2O formation. As a consequence, the composition and morphology of the Cu-Cu2O precipitate can be tuned by controlling pH of the aqueous CuSO4 solution during the -radiation induced synthesis.

  • 27. Liao, Rong-Zhen
    et al.
    Wang, Mei
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. Dalian University of Technology (DUT), China.
    Siegbahn, Per E. M.
    The mechanism of hydrogen evolution in Cu(bztpen)-catalysed water reduction: a DFT study2015In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 44, no 21, p. 9736-9739Article in journal (Refereed)
    Abstract [en]

    The mechanism of water reduction catalysed by a mononuclear copper complex Cu(bztpen) (bztpen = N-benzyl-N, N', N'-tris(pyridine-2-ylmethyl) ethylenediamine) has been elucidated by DFT calculations, revealing that hydrogen evolution proceeds via coupling of a Cu(II)-hydride and a pendant pyridinium, and providing important implications for the future design of new catalytic systems for water reduction.

  • 28.
    Lindsjo, Martin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Fischer, Andreas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
    Kloo, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
    Dimorphic (Ba GaCl4 (2))(3)center dot 2C(6)H(6): a case of coordination extremes2010In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 39, no 6, p. 1467-1469Article in journal (Refereed)
    Abstract [en]

    Two new dimorphic tris[bariumbis(tetrachloro gallate]) bisbenzene formed by the same molecular building blocks have been isolated and structurally characterized, showing an unprecedented inorganic as well as mixed organic/inorganic coordination.

  • 29.
    Lousada, Cláudio M.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Fernandes, Ricardo M. F.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Tarakina, Nadezda V.
    Soroka, Inna L.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Synthesis of copper hydride (CuH) from CuCO3·Cu(OH)2 – a path to electrically conductive thin films of Cu2017In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 46, no 20, p. 6533-6543Article in journal (Refereed)
    Abstract [en]

    The most common synthesis methods for copper hydride (CuH) employ hard ligands that lead to the formation of considerable amounts of metallic Cu as side-product. Here we explore a synthesis method for CuH(s) through the reaction of CuCO3 center dot Cu(OH)(2)(s) with hypophosphorous acid (H3PO2) in solution, via the formation of the intermediate Cu(H2PO2)(2)(aq) complex. The reaction products were characterized with XRD, FTIR and SEM at different reaction times, and the kinetics of the transformation of Cu(H2PO2)(2)(aq) to CuH(s) were followed with NMR and are discussed. We show that our synthesis method provides a simple way for obtaining large amounts of CuH(s) even when the synthesis is performed in air. Compared to the classic Wurtz method, where CuSO4 is used as an initial source of Cu2+, our synthesis produces CuH particles with less metallic Cu side-product. We attribute this to the fact that our reaction medium is free from the hard SO42- ligand that can disproportionate Cu(I). We discuss a mechanism for the reaction based on the known reactivity of the reagents and intermediates involved. We explored the possibility of using CuH(s) for making electrically conductive films. Tests that employed water-dispersed CuH particles show that this compound can be reduced with H3PO2 leading to electrically conductive thin films of Cu. These films were made on regular office paper and were found to be Ohmic conductors even after several weeks of exposure to ambient conditions. The fact that the synthesis reported here produces large amounts of CuH particles in aqueous media, with very little impurities, and the fact that these can then be converted to a stable electrically conductive film can open up new applications for CuH such as for printing electrically conductive films or manufacturing surface coatings.

  • 30. Lu, Z.
    et al.
    Gao, Y.
    Chen, H.
    Liu, Z.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. Dalian University of Technology (DUT), Dalian, China.
    Water oxidation catalyzed by a charge-neutral mononuclear ruthenium(III) complex2017In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 46, no 4, p. 1304-1310Article in journal (Refereed)
    Abstract [en]

    A new charge-neutral Ru(iii) complex RuL(pic)3 (1) (H3L = 3,6-di-tert-butyl-9H-carbazole-1,8-dicarboxylic acid, pic = 4-picoline) was synthesized and fully characterized. This complex promoted chemical and photochemical water oxidation efficiently with turnover frequencies of 0.28 s-1 and 5 min-1, respectively. In particular, for photochemical water oxidation, complex 1 showed excellent stability and good activity. The X-ray crystal structure, electrochemical results, and the detection of the RuIV-OH intermediate by high-resolution mass spectrometry revealed that complex 1 exchanged its 4-picoline ligand with water at the RuIII state to form the authentic water oxidation catalyst. The kinetics studies suggested a reaction mechanism involving nucleophilic attack by a water molecule.

  • 31.
    Macak, Peter
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Tsushima, Satoru
    Wahlgren, Ulf
    Grenthe, Ingmar
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
    A theoretical study of the fluoride exchange between UO2F+(aq) and UO22+(aq)2006In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, no 30, p. 3638-3646Article in journal (Refereed)
    Abstract [en]

    Experimental data on the thermodynamics and reaction mechanism of the inner-sphere. uoride exchange reaction (UO22+)-O-17 + UO2F+ reversible arrow (UO2F+)-O-17 + UO22+ have been compared with different intimate reaction mechanisms using quantum chemical methods. Two models have been tested that start from the outer sphere complexes, (H2O)[UAO2F(OH2)(4)(+)] center dot center dot center dot [UBO2(OH2)(5)(2+)] and [UAO2F(OH2)(4)(+)] center dot center dot center dot [UBO2(OH2)(5)(2+)]; the geometry and energies of the intermediates and transition states along possible reaction pathways have been calculated using different ab initio methods, SCF, B3LYP and MP2. Both the experimental data and the theoretical results suggest that the. uoride exchange takes place via the formation and breaking of a U - F - U bridge that is the rate determining step. The calculated activation enthalpy Delta H-not equal = 30.9 kJ mol(-1) is virtually identical to the experimental value 31 kJ mol(-1); however this agreement may be a coincidence as we do not expect a larger accuracy than 10 kJ mol(-1) with the methods used. The calculations show that the. uoride bridge is formed as an insertion of UAO2F(OH2)(4)(+) into UBO2(OH2)(5)(2+) followed by a subsequent transfer of water from the first to the second coordination sphere of U-B.

  • 32. Nenert, Gwilherm
    et al.
    Fabelo, Oscar
    Forsberg, Kerstin
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Colin, Claire V.
    Rodriguez-Carvajal, Juan
    Structural and magnetic properties of the low-dimensional fluoride beta-FeF3(H2O)(2)center dot H2O2015In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 44, no 31, p. 14130-14138Article in journal (Refereed)
    Abstract [en]

    We have reinvestigated the crystal structure of the low-dimensional fluoride beta-FeF3(H2O)(2)center dot H2O using high resolution neutron and X-ray diffraction data. Moreover we have studied the magnetic behavior of this material combining medium resolution and high flux neutron powder diffraction together with magnetic susceptibility measurements. This fluoride compound exhibits vertex-shared 1D Fe3+ octahedral chains, which are extended along the c-axis. The magnetic interactions between adjacent chains involve super-superexchange interactions via an extensive network of hydrogen bonds. This interchain hydrogen bonding scheme is sufficiently strong to induce a long range magnetic order appearing below T = 20(1) K. The magnetic order is characterized by the propagation vector k = (0, 0, 1/2), giving rise to a strictly antiferromagnetic structure where the Fe3+ spins are lying within the ab-plane. Magnetic exchange couplings extracted from magnetization measurements are found to be J(II)/k(b) = -18 K and J(perpendicular to)/k(b) = -3 K. These values are in good agreement with the neutron diffraction data, which show that the system became anti-ferromagnetically ordered at ca. T-N = 20(1) K.

  • 33. Palladino, Giuseppe
    et al.
    Szabo, Zoltan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
    Fischer, Andreas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
    Grenthe, Ingmar
    Structure, equilibrium and ligand exchange dynamics in the binary and ternary dioxouranium(VI)-ethylenediamine-N,N '-diacetic acid-fluoride system: a potentiometric, NMR and X-ray crystallographic study2006In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, no 43, p. 5176-5183Article in journal (Refereed)
    Abstract [en]

    The structure, thermodynamics and kinetics of the binary and ternary uranium(VI)-ethylenediamine- N,N'-diacetate (in the following denoted EDDA) fluoride systems have been studied using potentiometry, H-1, F-19 NMR spectroscopy and X-ray diffraction. The UO22+ - EDDA system could be studied up to - log[H3O+] = 3.4 where the formation of two binary complexes UO2(EDDA)(aq) and UO2(H(3)EDDA)(3+) were identified, with equilibrium constants log beta(UO(2)EDDA) = 11.63 +/- 0.02 and log beta(UO(2)H(3)EDDA(3+)) = 1.77 +/- 0.04, respectively. In the ternary system the complexes UO2(EDDA) F-, UO2(EDDA)(OH)(-) and (UO2)(2)(mu-OH)(2)(HEDDA)(2)F-2(aq) were identified; the latter through F-19 NMR. H-1 NMR spectra indicate that the EDDA ligand is chelate bonded in UO2(EDDA)(aq), UO2(EDDA) F- and UO2(EDDA)(OH)(-) while only one carboxylate group is coordinated in UO2(H(3)EDDA)(3+). The rate and mechanism of the fluoride exchange between UO2(EDDA) F- and free fluoride was studied by F-19 NMR spectroscopy. Three reactions contribute to the exchange; (i) site exchange between UO2(EDDA) F- and free fluoride without any net chemical exchange, (ii) replacement of the coordinated fluoride with OH- and (iii) the self dissociation of the coordinated fluoride forming UO2(EDDA)(aq); these reactions seem to follow associative mechanisms. H-1 NMR spectra show that the exchange between the free and chelate bonded EDDA is slow and consists of several steps, protonation/deprotonation and chelate ring opening/ring closure, the mechanism cannot be elucidated from the available data. The structure (UO2)(2)(EDDA)(2)(mu-H(2)EDDA) was determined by single crystal X-ray diffraction and contains two UO2( EDDA) units with tetracoordinated EDDA linked by H(2)EDDA in the zwitterion form, coordinated through a single carboxylate oxygen from each end to the two uranium atoms. The geometry of the complexes indicates that there is no geometric constraint for an associative ligand substitution mechanism.

  • 34. Shatskiy, Andrey
    et al.
    Lomoth, Reiner
    Abdel-Magied, Ahmed F.
    Rabten, Wangchuk
    Laine, Tanja M.
    Chen, Hong
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Sun, Junliang
    Andersson, Pher G.
    Karkas, Markus D.
    Johnston, Eric V.
    Akermark, Bjorn
    Catalyst solvent interactions in a dinuclear Ru-based water oxidation catalyst2016In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 45, no 47, p. 19024-19033Article in journal (Refereed)
    Abstract [en]

    Photocatalytic water oxidation represents a key process in conversion of solar energy into fuels and can be facilitated by the use of molecular transition metal-based catalysts. A novel straightforward approach for covalent linking of the catalytic units to other moieties is demonstrated by preparation of a dinuclear complex containing two [Ru(pdc)(pic)(3)]-derived units (pdc = 2,6-pyridinedicarboxylate, pic = 4-picoline). The activity of this complex towards chemical and photochemical oxidation of water was evaluated and a detailed insight is given into the interactions between the catalyst and acetonitrile, a common co-solvent employed to increase solubility of water oxidation catalysts. The solvent-induced transformations were studied by electrochemical and spectroscopic techniques and the relevant quantitative parameters were extracted.

  • 35.
    Soroka, Inna L.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Shchukarev, Andrey
    Jonsson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Tarakina, Nadezda V.
    Korzhavyi, Pavel A.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Cuprous hydroxide in a solid form: does it exist?2013In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 42, no 26, p. 9585-9594Article in journal (Refereed)
    Abstract [en]

    Experimental studies have been performed to obtain the unknown cuprous hydroxide compound, which has recently been predicted theoretically (P. A. Korzhavyi et. al., Proc. Natl. Acad. Sci. U. S. A., 2012, 109, 686-689) to be metastable in a solid form. The reduction of Cu2+ with ferrous ethylenediamine tetraacetate (EDTA) results in the formation of a yellow powder precipitate whose composition corresponds to CuOH x H2O as probed by Fourier Transform Infrared Spectroscopy (FTIR) and cryogenic X-ray Photoelectron Spectroscopy (XPS). A similar compound has been found on the surface of Cu-CuH powder stored in water, as detected by XPS. The reduction of Cu2+ to Cu+ with free radicals in aqueous solutions results in a Cu2O precipitate as the final product, while the formation of the yellow cuprous hydroxide colloids may be an intermediate step. Our studies reveal that cuprous hydroxide does exist in a solid form and most likely has a hydrated form, CuOH x H2O.

  • 36.
    Soroka, Inna
    et al.
    KTH, School of Chemical Science and Engineering (CHE).
    Tarakina, Nadezda V.
    Hermansson, Anton
    KTH, School of Chemical Science and Engineering (CHE).
    Bigum, Lukas
    KTH, School of Chemical Science and Engineering (CHE).
    Widerberg, Rickard
    KTH, School of Chemical Science and Engineering (CHE).
    Andersson, Mikael S.
    Mathieu, Roland
    Paulraj, Alagar R.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Radiation-induced synthesis of nanoscale Co- and Ni-based electro-catalysts on carbon for the oxygen reduction reaction2017In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 46, no 30, p. 9995-10002Article in journal (Refereed)
    Abstract [en]

    A facile synthesis of 3d-metal based electro-catalysts directly incorporated into a carbon support was carried out by.-radiation. Transition metals of period 4, i.e. Ni and Co, were precipitated and reduced from their respective salt solutions. The obtained materials were characterized by XRD, SEM, SQUID and the BET methods. Thereafter, the electrodes for fuel cells were fabricated out of synthesized material and their electrochemical performance for the oxygen reduction reaction in 6 M KOH was measured. Although the concentrations of Co and Ni in the electrode material were low (3.4% Co and 0.4% Ni) after reduction by irradiation, both the Ni and Co-based gas diffusion electrodes showed high catalytic activity for oxygen reduction both at room temperature and at 60 degrees C.

  • 37. Sun, Shiguo
    et al.
    He, Yanxia
    Yang, Zhigang
    Pang, Yi
    Liu, Fengyu
    Fan, Jiangli
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Peng, Xiaojun
    Synthesis and DNA photocleavage study of Ru(bpy)(3)(2+)-(CH2)(n)-MV2+ complexes2010In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 39, no 18, p. 4411-4416Article in journal (Refereed)
    Abstract [en]

    A series of Ru(bpy)(3)(2+)-(CH2)(n)-MV2+ complexes (1, n = 3, 4, 7) used for DNA photocleavage have been designed and synthesized. Under the irradiation of visible light, complexes 1 can cleave supercoiled plasmid DNA (pBR322) both in air and under Ar atmosphere. Radical species such as O2(-center dot), (OH)-O-center dot and the light-induced charge-separated (CS) oxidation state Ru(bpy)(3)(3+)-(CH2)(n)-MV+center dot are responsible for the cleavage. The longer the carbon chain linkage, the higher the DNA photocleavage efficiency. It is noted that backwards intramolecular electron transfer (ET) that exist in complexes 1 can lead to some decreasing effect on the cleavage result, while inclusion of complexes 1 with cucurbit[8]uril (CB[8]) inhibits the backwards ET to some extent, thereby increasing photocleavage efficiency.

  • 38. Sun, Shiguo
    et al.
    Li, Fusheng
    Liu, Fengyu
    Yang, Xue
    Fan, Jiangli
    Song, Fengling
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Peng, Xiaojun
    Synthesis and ECL performance of highly efficient bimetallic ruthenium tris-bipyridyl complexes2012In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 41, no 40, p. 12434-12438Article in journal (Refereed)
    Abstract [en]

    In order to find the ideal carbon chain linkage number n for achieving the highest ECL in bimetallic ruthenium tris-bipyridyl complexes, a series of novel complexes [(bpy)(2)Ru(bpy')(CH2)(n)(bpy')Ru(bpy)(2)](4+) (1, where bpy is 2,2'-bipyridyl, n = 10, 12, 14) for a coreactant electrochemiluminescence (ECL) system have been synthesized. Their ECL properties at a Au electrode have been studied in 0.1 M phosphate buffer by using tripropylamine (TPrA), 2-(dibutylamino)ethanol (DBAE) and melamine as the coreactant, to compare with that of the previously reported bimetallic ruthenium analogous complex [(bpy)(2)Ru(bpy')(CH2)(8)(bpy')Ru(bpy)(2)](4+). The results demonstrate that the ECL intensity depends largely on the length of the saturated carbon chain linkage number n. The highest ECL is reached when n = 10, suggesting that a synergistic effect on ECL enhancement co-exists between the two intramolecular linked ruthenium activating centers. Density functional theory (DFT) calculation demonstrated that the optimized bond distances between Ru and N(bpy') are the longest both in the ground and the excited triplet states in the case of n = 10, while those for Ru and N(bpy) are the shortest in the excited triplet states. All these factors may be responsible for the above mentioned results. This study provided a methodology to further improve and tune ECL efficiency by using bimetallic ruthenium complexes linked by a flexible saturated carbon chain.

  • 39. Sun, Shiguo
    et al.
    Yang, Yang
    Liu, Fengyu
    Fan, Jiangli
    Kehr, Jan
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Peng, Xiaojun
    ECL performance of ruthenium tris-bipyridyl complexes covalently linked with phenothiazine through different bridge2010In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 39, no 37, p. 8626-8630Article in journal (Refereed)
    Abstract [en]

    Three ruthenium complexes 1a, 1b and 1c were synthesized, in which the phenothiazine moiety was covalently linked to the ruthenium complex through a 4 carbon chain and amide bond, respectively. The results demonstrate that one PTZ moiety is preferred to reach a good ECL performance, and the 4 carbon chain linked complex 1a exhibits the highest ECL enhancement (up to about 9 times), in comparison with the commonly utilized parent Ru(bpy)(3)(2+), permitting a lower detection limit of 1.0 x 10(-14) M with signal to noise of 3 for 20 mM DBAE at Au electrode.

  • 40. Sun, Shiguo
    et al.
    Yang, Yang
    Liu, Fengyu
    Fan, Jiangli
    Peng, Xiaojun
    Kehr, Jan
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Intra- and intermolecular interaction ECL study of novel ruthenium tris-bipyridyl complexes with different amine reductants2009In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, no 38, p. 7969-7974Article in journal (Refereed)
    Abstract [en]

    A series of ruthenium(II) tris-bipyridyl complexes covalently linked with different amine reductants such as tripropylamine (TPrA), ethanolamine and diethanolamine for an electrochemiluminescence (ECL) system have been synthesized. Their ECL property at different working electrodes has been studied with and without the presence of TPrA, triethanolamine (TEOA) and 2-(dibutylamino) ethanol (DBAE) as the coreactant, respectively. The results demonstrate that the conjugated ruthenium complex alone can generate ECL through intramolecular interaction at a relatively low concentration, while with intermolecular interaction the ECL intensity increases progressively and becomes increasingly dominant with increasing complex concentration. For the coreactant system ECL, the amine coreactant needed for the conjugate complexes can be significantly lowered in comparison with that of the well known [Ru(bpy)(3)](2+)/TPrA system. One amine substituent is better for the system in order to diminish the steric hindrance, and the intramolecular amine reductant employed should have a similar structure with that of the additive amine coreactant to achieve a good ECL performance, which can pave a new route to further improving the ECL efficiency and increase the sensitivity of detection through combining both intra-and intermolecular interaction.

  • 41.
    Szabo, Zoltan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Vallet, Valerie
    Grenthe, Ingmar
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
    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 spectroscopy2010In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 39, no 45, p. 10944-10952Article in journal (Refereed)
    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).

  • 42. Vallet, V.
    et al.
    Szabo, Zoltan
    KTH, Superseded Departments, Chemistry.
    Grenthe, Ingmar
    KTH, Superseded Departments, Chemistry.
    Experimental and quantum chemical studies of structure and reaction mechanisms of dioxouranium(VI) complexes in solution2004In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, no 22, p. 3799-3807Article in journal (Refereed)
    Abstract [en]

    This perspective article describes the combination of experimental data and quantum chemical methods for the determination of structure and reaction mechanisms of uranyl( VI) complexes in aqueous solution. The first part assesses the accuracy of the chemical and thermodynamic properties of solvated uranyl( VI) complexes as obtained by various quantum chemical methods. The second part discusses structure determination, mechanisms for ligand exchange and the lability of coordinated water molecules for various uranyl( VI) complexes using a combination of NMR and quantum chemical data.

  • 43. Vallet, Valerie
    et al.
    Fischer, Andreas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
    Szabo, Zoltan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Grenthe, Ingmar
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
    The structure and bonding of Y, Eu, U, Am and Cm complexes as studied by quantum chemical methods and X-ray crystallography2010In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 39, no 33, p. 7666-7672Article in journal (Refereed)
    Abstract [en]

    Two isomers of Y/Eu(TTA)(3)(OH2) complexes and their structures were identified by single crystal X-ray diffraction, and their geometry and bond distances were also determined using quantum chemical (QM) methods. The data from the two methods agree very well, suggesting that QM is appropriate for calculating structures for which no experimental data are available. This method was therefore used to determine the structures of U/Am/Cm(TTA)(3)(OH2)(2) both in gas phase and in CPCM models of CCl4, CHCl3, and H2O. In these calculations the metal sites were described using the f-in-core approximation, comparing small- and large-core pseudopotentials (SPP and LPP) with their corresponding segmented basis sets. The difference between the Y/Eu-O bond distances between the LPP and SPP is less than 0.02 angstrom. However, in the actinide complexes the LPP results in larger An-O distances and the difference between the LPP and SPP results decreases from about 0.20 angstrom in the U-complex to 0.05 angstrom in the Am-and 0.04 angstrom in the Cm-complex. The chemical bonding studied by population analysis indicates that there is a significant back bonding in U(TTA)(3)(OH2)(2) from filled orbitals centered on uranium into empty pi* orbitals on coordinated oxygen; there is some evidence of back-bonding also in the americium complex, but a significantly smaller effect in the europium and curium species. The relative energy of the two isomers indicates they may be present in solution in comparable amounts, suggesting the possibility of exchange between them. The X-ray structures suggest two exchange pathways, a topological "twist" mechanism and a site exchange involving the opening of a TTA chelate ring.

  • 44. Vallet, Valerie
    et al.
    Szabo, Zoltan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Grenthe, Ingmar
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
    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 methods2011In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 40, no 13, p. 3154-3165Article in journal (Refereed)
    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.

  • 45. Viertelhaus, M.
    et al.
    Taylor, A. E.
    Kloo, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
    Gameson, I.
    Anderson, P. A.
    Silver nitrate in silver zeolite A: three-dimensional incommensurate guest ordering in a zeolite framework2006In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, no 19, p. 2368-2373Article in journal (Refereed)
    Abstract [en]

    We report the results of a detailed examination of the occlusion of silver nitrate in silver zeolite A (AgA). The superlattice reported to occur in (AgNO3)(9) - AgA was found to melt at between 80 and 100 degrees C on heating and reappear when the sample was cooled down to 80 degrees C. Annealing in this temperature range and rigorous exclusion of water produced an enhancement of the superlattice peaks, which results from ordering of the contents of the zeolite cages. Peaks assigned to the superlattice were indexed with the tetragonal lattice parameters a = 17.440( 5) and c = 12.398( 4) angstrom and proposed space group P4/nmm. The sharp peaks representing the lattice of the framework ( a = 12.3711( 5) angstrom, Pm (3) over barm) remained largely unaffected by the guest in this compound, which was found to exhibit strong negative thermal expansion. The host and guest lattices are incommensurate with the tetragonal guest lattice being slightly larger than the cubic host in the c-direction and slightly smaller in the a- and b-directions.

  • 46. Wang, Fujun
    et al.
    Wang, Mei
    Liu, Xiaoyang
    Jin, Kun
    Donga, Weibing
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Protonation, electrochemical properties and molecular structures of halogen-functionalized diiron azadithiolate complexes related to the active site of iron-only hydrogenases2007In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, no 34, p. 3812-3819Article in journal (Refereed)
    Abstract [en]

    Diiron complexes [{( mu-SCH2) 2NCH(2)C(6)H(4)X}{Fe( CO)(2)L}(2)] ( L = CO, X = 2-Br, 1; 2-F, 2; 3-Br, 3; L = PMe3, X = 2-Br, 4) were prepared as biomimetic models of the iron-only hydrogenase active site. The N-protonated species [ 1( NH)]+ClO4-, [ 2( NH)]+ClO4- and the mu-hydride diiron complex [ 4( FeHFe)]+PF6- were obtained in the presence of proton acids and well characterized. The protonation process of 4 was studied by in-situ IR and NMR spectroscopy, which suggests the formation of the diprotonated species [ 4( NH)( FeHFe)](2+) in the presence of an excess of proton acid. The molecular structures of 1, [ 1( NH)]+ClO4-, 4 and [ 4( FeHFe)]+PF6- were determined by X-ray crystallography. The single-crystal X-ray analysis reveals that an intramolecular H center dot center dot center dot Br contact ( 2.82 angstrom) in the crystalline state of [ 1( NH)]+ClO4-. In the presence of 1-6 equiv of the stronger acid HOTf, complex 1 is readily protonated on the bridged-N atom and can electrochemically catalyze the proton reduction at a relatively mild potential ( ca. -1.0 V). Complex 4 is also electrocatalytic active at -1.4 V in the presence of HOTf with formation of the mu-hydride diiron species.

  • 47. Wang, Mei
    et al.
    Chen, Lin
    Li, Xueqiang
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Approaches to efficient molecular catalyst systems for photochemical H(2) production using [FeFe]-hydrogenase active site mimics2011In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 40, no 48, p. 12793-12800Article in journal (Refereed)
    Abstract [en]

    The research on structural and functional biomimics of the active site of [FeFe]-hydrogenases is in an attempt to elucidate the mechanisms of H(2)-evolution and uptake at the [FeFe]-hydrogenase active site, and to learn from Nature how to create highly efficient H(2)-production catalyst systems. Undoubtedly, it is a challenging, arduous, and long-term work. In this perspective, the progresses in approaches to photochemical H(2) production using mimics of the [FeFe]-hydrogenase active site as catalysts in the last three years are reviewed, with emphasis on adjustment of the redox potentials and hydrophilicity of the [FeFe]-hydrogenase active site mimics to make them efficient catalysts for H(2) production. With gradually increasing understanding of the chemistry of the [FeFe]-hydrogenases and their mimics, more bio-inspired proton reduction catalysts with significantly improved efficiency of H(2) production will be realized in the future.

  • 48. Wang, Mei
    et al.
    Na, Yong
    Gorlov, Mikhail
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Light-driven hydrogen production catalysed by transition metal complexes in homogeneous systems2009In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, no 33, p. 6458-6467Article in journal (Refereed)
    Abstract [en]

    The development of heterogeneous catalytic systems for hydrogen production from water under light irradiation has been investigated during last three decades. Homogeneous photocatalysts, however, are very attractive in sense that their chemical and photochemical properties can be understood and tuned on molecular level. Moreover, in homogeneous systems catalysts may be covalently bound to photosensitizers, which leads to more efficient electron transfer. Molecular devices for water splitting based on such a systems are of great interest. In this review, we summarize recent progresses in the synthesis, properties and application of metal-based molecular catalysts for photoinduced hydrogen evolution in homogeneous systems.

  • 49. Wang, Ning
    et al.
    Wang, Mei
    Chen, Lin
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Reactions of [FeFe]-hydrogenase models involving the formation of hydrides related to proton reduction and hydrogen oxidation2013In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 42, no 34, p. 12059-12071Article in journal (Refereed)
    Abstract [en]

    [FeFe]-hydrogenases are enzymes in nature that catalyze the reduction of protons and the oxidation of H-2 at neutral pH with remarkably high activities and incredibly low overpotential. Structural and functional biomimicking of the active site of [FeFe]-hydrogenases can provide helpful hints for elucidating the mechanism of H-2 evolution and uptake at the [FeFe]-hydrogenase active site and for designing bio-inspired catalysts to replace the expensive noble metal catalysts for H-2 generation and uptake. This perspective focuses on the recent progress in the formation and reactivity of iron hydrides closely related to the processes of proton reduction and hydrogen oxidation mediated by diiron dithiolate complexes. The second section surveys the bridging and terminal hydride species formed from various diiron complexes as well as the intramolecular proton transfer. The very recent progress in H-2 activation by diiron dithiolate models are reviewed in the third section. In the concluding remarks and outlook, the differences in structure and catalytic mechanism between the synthetic models and the native [FeFe]-H(2)ase active site are compared and analyzed, which may cause the need for a significantly larger driving force and may lead to lower activities of synthetic models than the [FeFe]-H(2)ases for H-2 generation and uptake.

  • 50.
    Wang, Ying
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ahlquist, Mårten S. G.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    A computational study of the mechanism for water oxidation by (bpc)(bpy)(RuOH2)-O-II2014In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 43, no 36, p. 13776-13782Article in journal (Refereed)
    Abstract [en]

    A mechanistic study on the catalytic cycle water oxidation with 1 [(bpc)(bpy)(RuOH2)-O-II](+) (Hbpc = 2,2'-bipyridine-6-carboxylic acid, bpy = 2,2'-bipyridine) is described in this paper. Stepwise oxidation via proton-coupled electron transfer gives 3 [(bpc)(bpy)Ru-IV=O](+). An active 4 [(bpc)(bpy)Ru-V=O](2+), which is involved in the OO bond formation is generated from further 1e(-) oxidation of 3. Another different possible reaction at 4 was investigated and new destructive paths involving overoxidation of the metal were identified. The most viable path for OO bond formation via a water nucleophilic attack at the oxo of 4 is found to be the rate-determining step in this water oxidation catalytic cycle, and the hydro-peroxo 6 [(bpc)(bpy)-(RuOOH)-O-III](+) is generated accompanied with a proton transfer. The super-oxo 7(side-on) [(bpc)(bpy)(RuOO)-O-IV](+) and 8(side-on) [(bpc)(bpy)(RuOO)-O-V](2+), both low spin species, are generated by further oxidations of 6. Through an intersystem crossing they can transform to their high spin states, 9(end-on) [(bpc)(bpy)(RuOO)-O-IV](+) and 12(end-on) [(bpc)(bpy)(RuOO)-O-V](2+), respectively. Following a dissociative pathway O-2 is readily generated from both 9(end-on) and 12(end-on).

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