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  • 1. Abrahamsson, M. L. A.
    et al.
    Baudin, H. B.
    Tran, A.
    Philouze, C.
    Berg, K. E.
    Raymond-Johansson, M. K.
    Sun, Licheng C.
    Akermark, B.
    Styring, S.
    Hammarstrom, L.
    Ruthenium-manganese complexes for artificial photosynthesis: Factors controlling intramolecular electron transfer and excited-state quenching reactions2002Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 41, nr 6, s. 1534-1544Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Continuing our work toward a system mimicking the electron-transfer steps from manganese to P-680(+) in photosystem II (PS II), we report a series of ruthenium(II)-manganese(II) complexes that display intramolecular electron transfer from manganese(II) to photooxidized ruthenium(III). The electron-transfer rate constant (k(ET)) values span a large range, 1 X 10(5)-2 x 10(7) s(-1), and we have investigated different factors that are responsible for the variation. The reorganization energies determined experimentally (lambda = 1.5-2.0 eV) are larger than expected for solvent reorganization in complexes of similar size in polar solvents (typically lambda approximate to 1.0 eV). This result indicates that the inner reorganization energy is relatively large and, consequently, that at moderate driving force values manganese complexes are not fast donors. Both the type of manganese ligand and the link between the two metals are shown to be of great importance to the electron-transfer rate. In contrast, we show that the quenching of the excited state of the ruthenium(II) moiety by manganese(II) in this series of complexes mainly depends on the distance between the metals. However, by synthetically modifying the sensitizer so that the lowest metal-to-ligand charge transfer state was localized on the nonbridging ruthenium(II) ligands, we could reduce the quenching rate constant in one complex by a factor of 700 without changing the bridging ligand. Still, the manganese(II)-ruthenium (III) electrontransfer rate constant was not reduced. Consequently, the modification resulted in a complex with very favorable properties.

  • 2. Abrahamsson, M.
    et al.
    Wolpher, H.
    Johansson, O.
    Larsson, J.
    Kritikos, M.
    Eriksson, L.
    Norrby, P. O.
    Bergquist, J.
    Sun, Licheng C.
    Akermark, B.
    Hammarstrom, L.
    A new strategy for the improvement of photophysical properties in ruthenium(II) polypyridyl complexes. Synthesis and photophysical and electrochemical characterization of six mononuclear ruthenium(II) bisterpyridine-type complexes2005Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 44, nr 9, s. 3215-3225Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The synthesis and characterization of six ruthenium(II) bistridentate polypyridyl complexes is described. These were designed on the basis of a new approach to increase the excited-state lifetime of ruthenium(II) bisterpyridine-type complexes. By the use of a bipyridylpyridyl methane ligand in place of terpyridine, the coordination environment of the metal ion becomes nearly octahedral and the rate of deactivation via ligand-field (i.e., metal-centered) states was reduced as shown by temperature-dependent emission lifetime studies. Still, the possibility to make quasi-linear donor-ruthenium-acceptor triads is maintained in the complexes. The most promising complex shows an excited-state lifet me of tau = 15 ns in alcohol solutions at room temperature, which should be compared to a lifetime of tau = 0.25 ns for [Ru(tpy)(2)](2+). The X-ray structure of the new complex indeed shows a more octahedral geometry than that of [Ru(tpy)(2)](2+). Most importantly, the high excited-state energy was retained, and thus, so was the potential high reactivity of the excited complex, which has not been the case with previously published strategies based on bistridentate complexes.

  • 3. Baranov, A. I.
    et al.
    Isaeva, A. A.
    Kloo, Lars A.
    KTH, Tidigare Institutioner                               , Kemi.
    Popovkin, B. A.
    New metal-rich sulfides Ni6SnS2 and Ni9Sn2S2 with a 2D metal framework: Synthesis, crystal structure, and bonding2003Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 42, nr 21, s. 6667-6672Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two new, metal-rich nickel-tin sulfides Ni6SnS2 and Ni9Sn2S2 were found by establishing phase relations in the ternary Ni-Sn-S system at 540 degreesC. Their single crystals were prepared by means of chemical vapor transport reactions. Single crystal X-ray diffraction was used for the determination of their crystal structures. Both compounds crystallize in a tetragonal system (/4/mmm, No. 139, Z = 2, a = 3.646(1) Angstrom, c = 18.151(8) Angstrom for Ni6SnS2, and a = 3.678(1) Angstrom, c = 25.527(8) Angstrom for Ni9Sn2S2). Their crystal structures represent a new structure type and can be considered as assembled from bimetallic nickel-tin and nickel-sulfide slabs alternating along the crystallographic c axis. DFT band structure calculations showed the bonding within the bimetallic slabs to have a delocalized, multicenter nature, typical for metallic systems, and predominantly classical, pairwise bonding between nickel and sulfur.

  • 4. Baranov, A. I.
    et al.
    Kloo, Lars A.
    KTH, Tidigare Institutioner                               , Kemi.
    Olenev, A. V.
    Popovkin, B. A.
    Romanenko, A. I.
    Quasi-1D cations (1)(infinity) Ni8Bi8S (n+) of variable charge: Infinite columns (1)(infinity) Ni8Bi8S (2+) in the novel compound Ni(8)Bi(8)Sl(2)2003Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 42, nr 13, s. 3988-3993Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The new compound Ni(8)Bi(8)Sl(2) has been synthesized and its crystal structure determined by X-ray crystallography. The structure contains one-dimensional (1D) cations (1)(infinity)[Ni8Bi8S](2+) separated by iodine anions. The geometry of the columns is similar to that of the recently reported (1)(infinity)[Ni8Bi8S](+), and the main difference between them is only their formal charge. Electronic structure calculations and physical properties measurements were performed to analyze the influence of the number of valence electrons on the bonding and properties of compounds containing these 1D cations. It was shown that the removal of one electron (i.e., (1)(infinity)[Ni8Bi8S](+) --> (1)(infinity)[Ni8Bi8S](2+)) mainly affects the Ni-S bonding within the cation and essentially has no influence on the intermetallic Ni-Bi bonding. It was found that Ni(8)Bi(8)Sl(2) containing double-charged columns has conductivity properties more similar to a pure 1D metal than the congener Ni(8)Bi(8)Sl containing mono-charged columns.

  • 5. Benson, D.
    et al.
    Li, Y.
    Luo, Wei
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik. Condensed Matter Theory Group, Department of Physics and Astronomy, Uppsala University, SE-751 20 Uppsala, Sweden .
    Ahuja, Rajeev
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik. Condensed Matter Theory Group, Department of Physics and Astronomy, Uppsala University, SE-751 20 Uppsala, Sweden .
    Svensson, G.
    Häussermann, U.
    Lithium and calcium carbides with polymeric carbon structures2013Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 52, nr 11, s. 6402-6406Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We studied the binary carbide systems Li2C2 and CaC2 at high pressure using an evolutionary and ab initio random structure search methodology for crystal structure prediction. At ambient pressure Li2C2 and CaC2 represent salt-like acetylides consisting of C2 2- dumbbell anions. The systems develop into semimetals (P3Ì...m1-Li2C2) and metals (Cmcm-Li2C2, Cmcm-CaC2, and Immm-CaC2) with polymeric anions (chains, layers, strands) at moderate pressures (below 20 GPa). Cmcm-CaC2 is energetically closely competing with the ground state structure. Polyanionic forms of carbon stabilized by electrostatic interactions with surrounding cations add a new feature to carbon chemistry. Semimetallic P3Ì...m1-Li2C 2 displays an electronic structure close to that of graphene. The π* band, however, is hybridized with Li-sp states and changed into a bonding valence band. Metallic forms are predicted to be superconductors. Calculated critical temperatures may exceed 10 K for equilibrium volume structures.

  • 6. Bi, L. -H
    et al.
    Al-Kadamany, G.
    Chubarova, Elena V.
    Jacobs University, United States .
    Dickman, M. H.
    Chen, L.
    Gopala, D. S.
    Richards, R. M.
    Kelta, B.
    Nadjo, L.
    Jaensch, H.
    Mathys, G.
    Kortz, U.
    Organo-ruthenium supported heteropolytungstates: synthesis, structure, electrochemistry, and oxidation catalysis2009Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 48, nr 21, s. 10068-10077Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The reaction of [Ru(arene)Cl2]2 (arene = benzene, p-cymene) with [X2W22O74(OH)2] 12- (X = SbIII, BiIII) In buffer medium resulted In four organo-ruthenium supported heteropolytungstates, [Sb 2W20O70(RuC6H6) 2]10 (1), [Bi2W20O 70(RuC6H6)2]10- (2), [Sb2W20O7o(RuC10H14) 2]10- (3), and [Bi2W20O 70(RuC10H14)2]10- (4), which have been characterized in solution by multinuclear (183W, 13C, 1H) NMR, UV-vis spectroscopy, electrochemistry, and in the solid state by single-crystal X-ray diffraction, IR spectroscopy, thermogravimetric analysis, and elemental analysis. Polyanions 1, 2, and 4 crystallize in the triclinic system, space group P1 with the following unit cell parameters: K5Na5[Sb2W20O 7o(RuC6H6)2]·22H 2O (KNa-1), a= 12.1625(2)Å, b = 13.1677(2) Å, C= 16.0141(3)Å α = 78.9201 (7)°, β = 74.4442(8)°, γ = 78.9019(8)°, and Z= 1 ; Cs2Na8[Bi2W 20O7o(RuC6H6)2] · 30H2O (CsNa-2), a = 11.6353(7) Å b = 13.3638(7) Å, C= 16.7067(8) Å, a = 79.568(2)°, β = 71.103(2)°, γ = 80.331(2)°, and Z= 1; Na10[Bi2W20O 70(RuC10H14)2]-35H20 (Na-4), a = 15.7376(12) Å b = 15.9806(13) Å, c = 24.2909(19) Å, α = 92.109(4)°, β = 101.354(4)°, γ = 97.365(3)°, and Z= 2. Polyanions 1-4 consist of two (L)Ru2+ (L = benzene or p-cymene) units linked to a [X2W20O70]14 (X=Sb III BiIII fragment via Ru-O(W) bonds resulting in an assembly with idealized C2h symmetry. Polyanions 1-4 are stable in solution as indicated by the expected 183W, 13C, and 1H NMR spectra. The electrochemistry of 1-4 is described by considering the reduction and the oxidation processes. The nature of the arene In Ru(arene) has practically no influence on the formal potentials of the W-centers, which are more sensitive to the Sb or Bi hetera atoms. The results suggest that the respective Sb- and Bi derivatives have very different pK a values, with the reduced form of 1 being the most basic, thus permitting the observation of two well-developed voltammetric waves at pH 6. In contrast, the identity of the arene influences the oxidation processes, thus permitting to distinguish them. A strong electrocatalytic water oxidation peak is observed that is more positive than the one corresponding to the Ru(arene) oxidation process. Also a stepwise oxidation of the Ru(benzene) group could be observed at pH 3. The catalytic efficiency, on the other hand, of 1-4 toward the oxidation of n-hexadecane and p-xylene illustrated the effect of ruthenium substitution on the polyanion catalytic performance.

  • 7. Blomberg, Margareta R. A.
    et al.
    Johansson, Adam Johannes
    Stockholm University.
    Siegbahn, Per E. M.
    O-O bond cleavage in dinuclear peroxo complexes of iron porphyrins: a quantum chemical study2007Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 46, nr 19, s. 7992-7997Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To gain insight into the mechanisms of O-2 activation and cleavage in metalloenzymes, biomimetic metal complexes have been constructed and experimentally characterized. One such model complex is the dinuclear peroxo complex of iron porphyrins observed at low temperature in a noncoordinating solvent. The present theoretical study examines the O-O bond cleavage in these complexes, experimentally observed to occur either at increased temperature or when a strongly coordinating base is added. Using hybrid density functional theory, it is shown that the O-O bond cleavage always occurs in a state where two low-spin irons (S = +/- 1/2) are antiferromagnetically coupled to a diamagnetic state. This state is the ground state when the strong base is present and forms an axial ligand to the free iron positions. In contrast, without the axial ligands, the ground state of the clinuclear peroxo complex has two high-spin irons (S = +/- 5/2) coupled antiferromagnetically. Thus, the activation barrier for O-O bond cleavage is higher without the base because it includes also the promotion energy from the ground state to the reacting state. It is further found that this excitation energy, going from 10 unpaired electrons in the high-spin case to 2 in the low-spin case, is unusually difficult to determine accurately from density functional theory because it is extremely sensitive to the amount of exact exchange included in the functional.

  • 8. Bodor, A.
    et al.
    Toth, I.
    Banyai, I.
    Szabo, Zoltan
    KTH, Tidigare Institutioner                               , Kemi.
    Hefter, G. T.
    F-19 NMR study of the equilibria and dynamics of the Al3+/F- system2000Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 39, nr 12, s. 2530-2537Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A careful reinvestigation by high-field F-19 NMR (470 MHz) spectroscopy has been made of the Al3+/F- system in aqueous solution under carefully controlled conditions of pH, concentration, ionic strength (I), and temperature. The F-19 NMR spectra show five distinct signals at 278 K and I = 0.6 M (TMACl) which have been attributed to the complexes AlFi(3-i)+(aq) with i less than or equal to 5. There was no need to invoke AlFi(OH)(j)((3-i-j)+) mixed complexes in the model under our experimental conditions (pH less than or equal to 6.5), nor was any evidence obtained for the formation of AlF63-(aq) at very high ratios of F-/Al3+. The stepwise equilibrium constants obtained for the complexes by integration of the F-19 signals are in good agreement with literature data given the differences in medium and temperature. In I = 0.6 M TMACl at 278 K and in I = 3 M KCl at 298 K the log K-i values are 6.42, 5.31, 3.99, 2.50, and 0.84 (for species i = 1-5) and 6.35, 5.25, and 4.11 (for species i = 1-3), respectively. Disappearance of the F-19 NMR signals under certain conditions was shown to be due to precipitation. Certain 19F NMR signals exhibit temperature- and concentration-dependent exchange broadening. Detailed line shape analysis of the spectra and magnetization transfer measurements indicate that the kinetics are dominated by F- exchange rather than complex formation. The detected reactions and their rate constants are AlF22+ + *F- reversible arrow AIF*F2+ + F- (k(02) = (1.8 +/- 0.3) x 10(6) M-1 s(-1)), AlF30 + *F- reversible arrow (AlF2F0)-F-* + F- (k(03) = (3.9 +/- 0.9) x 10(6) M-1 s(-1)), and AlF30 + H*F reversible arrow AlF2*F-0 + HF (k(03)(H) = (6.6 +/- 0.5) x 10(4) M-1 s(-1)). The rates of these exchange reactions increase markedly with increasing F- substitution. Thus, the reactions of AlF2+(aq) were too inert to be detected even on the T-1 NMR time scale, while some of the reactions of AlF30(aq) were fast, causing large line broadening. The ligand exchange appears to follow an associative interchange mechanism. The cis-trans isomerization of AlF2+(aq), consistent with octahedral geometry for that complex, is slowed sufficiently to be observed at temperatures around 270 R. Difference between the Al3+/F- system and the much studied Al3+/OH- system are briefly commented on.

  • 9. Borgstrom, M.
    et al.
    Johansson, O.
    Lomoth, R.
    Baudin, H. B.
    Wallin, S.
    Sun, Licheng C.
    Akermark, B.
    Hammarstrom, L.
    Electron donor-acceptor dyads and triads based on tris(bipyridine)ruthenium(II) and benzoquinone: Synthesis, characterization, and photoinduced electron transfer reactions2003Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 42, nr 17, s. 5173-5184Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two electron donor-acceptor triads based on a benzoquinone acceptor linked to a light absorbing [Ru(bpy)(3)](2+) complex have been synthesized. In triad 6 (denoted Ru-II-BQ-Co-III), a [Co(bpy)(3)](3+) complex, a potential secondary acceptor, was linked to the quinone. In the other triad, 8 (denoted PTZ-Ru-II-BQ), a phenothiazine donor was linked to the ruthenium moiety. The corresponding dyads Ru-II-BQ (4) and PTZ-Ru-II (9) were prepared for comparison. Upon light excitation in the visible band of the ruthenium moiety, electron transfer to the quinone occurred with a rate constant k(1) = 5 x 10(9) s(-1) (tau(1) = 200 ps) in all the quinone containing complexes. Recombination to the ground state followed, with a rate constant k(b) similar to 4.5 x 10(8) s(-1) (tau(b) similar to 2.2 ns), for both Ru-II-BQ and Ru-II-BQ-Co-III with no indication of a charge shift to generate the reduced Coll moiety. In the PTZ-Ru-II-BQ triad, however, the initial charge separation was followed by a rapid (k > 5 x 10(9) s(-1)) electron transfer from the phenothiazine moiety to give the fairly long-lived PTZ(.+)-Ru-II-BQ(.-) state (tau = 80 ns) in unusually high yield for a [Ru(bPY)(3)](2+)- based triad (> 90%), that lies at DeltaGdegrees = 1.32 eV relative to the ground state. Unfortunately, this triad turned out to be rather photolabile. Interestingly, coupling between the oxidized PTZ(.+) and the BQ(.-) moieties seemed to occur. This discouraged further extension to incorporate more redox active units. Finally, in the dyad PTZ-Ru-II a reversible, near isoergonic electron transfer was observed on excitation. Thus, a quasiequilibrium was established with an observed time constant of 7 ns, with ca. 82% of the population in the PTZ-Ru-*(II) state and 18% in the PTZ(.+)Ru(II)(bpy(.-)) state. These states decayed in parallel with an observed lifetime of 90 ns. The initial electron transfer to form the PTZ(.+)-Ru-II(bpy(.-)) state was thus faster than what would have been inferred from the Ru-*(II) emission decay (tau = 90 ns). This result suggests that reports for related PTZ-Ru-II and PTZ-Ru-II-acceptor complexes in the literature might need to be reconsidered.

  • 10. Chen, C. N.
    et al.
    Huang, D. G.
    Zhang, X. F.
    Chen, F.
    Zhu, H. P.
    Liu, Q. T.
    Zhang, C. X.
    Liao, D. Z.
    Li, L.
    Sun, Licheng C.
    Aggregate manganese Schiff base moieties by terephthalate or acetate: Dinuclear manganese and trinuclear mixed metal Mn-2/Na complexes2003Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 42, nr 11, s. 3540-3548Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A reaction system consisting of terephthalic acid, NaOH, inorganic Mn(II) or Mn(III) salt, and salicylidene alkylimine resulted in dinuclear manganese complexes (salpn)(2)Mn-2(mu-phth)(CH3OH)(2) (1, salpn = N,N'-1,3-propylene-bis(salicylideneiminato); phth = terephthalate dianion), (salen)(2)Mn-2(mu-phth)(CH3OH)(2) (2, salen = N,N'-ethylene-bis(salicylideneiminato)), (salen)(2)Mn-2(mu-phth)(CH3OH)(H2O) (3), and (salen)(2)Mn-2(mu-phth) (4), while the absence of NaOH in the reaction led to a mononuclear Mn complex (salph)Mn(CH3OH)(NO3) (5, salph = N,N'-1,2-phenylene-bis(salicylideneiminato)). In addition, a trinuclear mixed metal complex H{Mn2Na(salpn)(2)(mu-OAc)(2)(H2O)(2)}(OAc)(2) (6) was obtained from the reaction system by using maleic acid instead of terephthalic acid. Five-coordinate Mn ions were found in 4 giving rise to an intermolecular interaction and constructing a one-dimensional linear structure. Antiferromagnetic exchange interactions were observed for 1-3, and a total ferromagnetic exchange of 4 was considered to stem from intermolecular magnetic coupling. H-1 NMR signals of phenolate ring and alkylene (or phenylene) backbone of the diamine are similar to those reported in the literature, and the phth protons are at -2.3 to -10.1 ppm. Studies on structure, bond valence sum analysis, and magnetic properties indicate the oxidation states of the Mn ions in 6 to be +3, which are also indicated by ESR spectra in dual mode. Ferromagnetic exchange interaction between the Mn(III) sites was observed with J = 1.74 cm(-1). A quasireversible redox pair at -0.29V/0.12V has been assigned to the redox of Mn-2(III)/Mn(III)Mn(II), implying the intactness of the complex backbone in solution.

  • 11. Chen, Hong
    et al.
    Zhao, Huishuang
    Yu, Zheng-Bao
    Wang, Lei
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Sun, Licheng
    Sun, Junliang
    Construct Polyoxometalate Frameworks through Covalent Bonds2015Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 54, nr 17, s. 8699-8704Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An emerging strategy for exploring the application of polyoxometalates (POMs) is to assemble POM clusters into open-framework materials, especially inorganic organic hybrid three-dimensional (3D) open-framework materials, via the introduction of different organic linkers between the POM clusters. This strategy has yielded a few 3D crystalline POMs of which a typical class is the group of polyoxometalate metal organic frameworks (POMMOFs). However, for reported POMMOFs, only coordination bonds are involved between the linkers and POM clusters, and it has not yet produced any covalently bonded polyoxometalate frameworks. Here, the concept of "covalently bonded POMs (CPOMs)" is developed. By using vanadoborates as an example, we showed that the 3D CPOMs can be obtained by a condensation reaction through the oxolation mechanism of polymer chemistry. In particular, suitable single crystals were harvested and characterized by single-crystal X-ray diffraction. This work forges a link among polymer science, POM chemistry, and open-framework materials by demonstrating that it is possible to use covalent bonds according to polymer chemistry principles to construct crystalline 3D open-framework POM materials.

  • 12. Chen, Lin
    et al.
    Wang, Mei
    Gloaguen, Frederic
    Zheng, Dehua
    Zhang, Peili
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Tetranuclear Iron Complexes Bearing Benzenetetrathiolate Bridges as Four-Electron Transformation Templates and Their Electrocatalytic Properties for Proton Reduction2013Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 52, nr 4, s. 1798-1806Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two tetranuclear iron-sulfur complexes, (mu,mu-pbtt)[Fe-2(CO)(6)](2) (pbtt = benzene-1,2,4,5-tetrathiolato, 3) and (mu,mu-obtt)[Fe-2(CO)(6)](2) (obtt = benzene-1,2,3,4-tetrathiolato, 4), were prepared from reaction of Fe-3(CO)(12) and the corresponding tetramercaptobenzene in THF, respectively. Complexes 5 and 6, (mu,mu-pbtt)[Fe-2(CO)(5)L-1][Fe-2(CO)(5)L-2] (L-1 = CO, L-2 = PPyr(3) (Pyr = N-pyrrolyl), 5; L-1 = L-2 = PPyr(3), 6) were obtained by controlling CO displacement of 3 with PPyr(3). Molecular structures of 3-6 were determined by spectroscopic and single-crystal X-ray analyses. All-CO Fe4S4 complexes 3 and 4 each display four-electron reduction processes in consecutive chemically reversible two-electron reduction events with relatively narrow potential spans in the cyclic voltammograms. Phosphine-substituted Fe4S4 complexes 5 and 6 exhibit two consecutive two-electron reduction events, which are not fully reversible. The electrocatalytic properties of 3 and 4 for proton reduction were studied using a series of carboxylic acids of increasing strength (CH3COOH, CH2ClCOOH, CHCl2COOH, CCl3COOH, and CF3COOH). The mechanisms for electrochemical proton reduction to hydrogen catalyzed by complex 3 as a function of acid strength are discussed.

  • 13. Chen, W. Z.
    et al.
    Liu, F. H.
    Matsumoto, K.
    Autschbach, J.
    Le Guennic, B.
    Ziegler, T.
    Maliarik, M.
    Glaser, Julius
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Spectral and structural characterization of amidate-bridged platinum-thallium complexes with strong metal-metal bonds2006Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 45, nr 11, s. 4526-4536Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The reactions of [Pt(NH3)(2)((NHCOBu)-Bu-t)(2)] and TlX3 (X = NO3-, Cl-, CF3CO2-) yielded dinuclear [{Pt(ONO2)(NH3)(2-)((NHCOBu)-Bu-t)}Tl(ONO2)(2)(MeOH)] (2) and trinuclear complexes [{PtX(RNH2)(2)((NHCOBu)-Bu-t)(2)}(2)Tl](+) [X = NO3- (3), Cl- (5), CF3CO2- (6)], which were spectroscopically and structurally characterized. Strong Pt-Tl interaction in the complexes in solutions was indicated by both Pt-195 and Tl-205 NMR spectra, which exhibit very large one-bond spin-spin coupling constants between the heteronuclei ((1)J(PtTl)), 146.8 and 88.84 kHz for 2 and 3, respectively. Both the X-ray photoelectron spectra and the Pt-195 chemical shifts reveal that the complexes have Pt centers whose oxidation states are close to that of Pt-III. Characterization of these complexes by X-ray diffraction analysis confirms that the Pt and Tl atoms are held together by very short Pt-Tl bonds and are supported by the bridging amidate ligands. The Pt-Tl bonds are shorter than 2.6 angstrom, indicating a strong metal-metal attraction between these two metals. Compound 2 was found to activate the C-H bond of acetone to yield a platinum(IV) acetonate complex. This reactivity corresponds to the property of Pt-III complexes. Density functional theory calculations were able to reproduce the large magnitude of the metal-metal spin-spin coupling constants. The couplings are sensitive to the computational model because of a delicate balance of metal 6s contributions in the frontier orbitals. The computational analysis reveals the role of the axial ligands in the magnitude of the coupling constants.

  • 14.
    Duan, Lele
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Wang, Lei
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Inge, A. Ken
    Fischer, Andreas
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Zou, Xiaodong
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Insights into Ru-Based Molecular Water Oxidation Catalysts: Electronic and Noncovalent-Interaction Effects on Their Catalytic Activities2013Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 52, nr 14, s. 7844-7852Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A series of Ru-bda water oxidation catalysts [Ru(bda)L-2] (H(2)bda = 2,2'-bipyridine-6,6'-dicarboxylic acid; L = [HNEt3][3-SO3-pyridine], 1; 4-(EtOOC)-pyridine, 2; 4-bromopyridine, 3; pyridine, 4; 4-methoxypyridine, 5; 4-(Me2N)-pyridine, 6; 4-[Ph(CH2)(3)]-pyridine, 7) were synthesized with election-donating/-withdrawing groups and hydro-philic/hydrophobic groups in the axial ligands. These complexes were characterized by H-1 NMR spectroscopy, high-resolution mass spectrometry, elemental analysis, and electrochemistry. In addition, complexes 1 and 6 were further identified by single crystal X-ray crystallography, revealing a highly distorted octahedral configuration of the Ru coordination sphere. All of these complexes are highly active toward Ce-IV-driven (Ce-IV = Ce(NH4)(2)(NO3)(6)) water oxidation with oxygen evolution rates up to 119 mols of O-2 per mole of catalyst per second. Their structure-activity relationship was investigated. Electron-withdrawing and noncovalent interactions (attraction) exhibit positive effect on the catalytic activity of Ru-bda catalysts.

  • 15.
    Duan, Lele
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Xu, Yunhua
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Zhang, Pan
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Wang, Mei
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Visible Light-Driven Water Oxidation by a Molecular Ruthenium Catalyst in Homogeneous System2010Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 49, nr 1, s. 209-215Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Discovery of an efficient catalyst bearing low overpotential toward water oxidation is a key step for light-driven water splitting into dioxygen and dihydrogen. A mononuclear ruthenium complex, Ru(II)L(pic)(2) (1) (H2L = 2,2'-bipyridine-6,6'-dicarboxylic acids pic = 4-picoline), was found capable of oxidizing water eletrochemically at a relatively low potential and promoting light-driven water oxidation using a three-component system composed of a photosensitizer, sacrificial electron acceptor, and complex 1. The detailed electrochemical properties of 1 were studied, and the onset potentials of the electrochemically catalytic curves in pH 7.0 and pH 1.0 solutions are 1.0 and 1.5 V, respectively. The low catalytic potential of 1 under neutral conditions allows the use of [Ru(bpy)(3)](2+) and even [Ru(dmbpy)(3)](2+) as a photosensitizer for photochemical water oxidation. Two different sacrificial electron acceptors, [Co(NH3)(5)Cl]Cl-2 and Na2S2O8, were used to generate the oxidized state of ruthenium tris(2,2'-bipyridyl) photosensitizers. In addition, a two-hour photolysis of I in a pH TO phosphate buffer did not lead to obvious degradation, indicating the good photostability of our catalyst. However, under conditions of light-driven water oxidation, the catalyst deactivates quickly. In both solution and the solid state under aerobic conditions, complex 1 gradually decomposed via oxidative degradation of its ligands, and two of the decomposed products, sp(3) C-H bond oxidized Ru complexes, were identified. The capability of oxidizing the sp(3) C-H bond implies the presence of a highly oxidizing Ru species, which might also cause the final degradation of the catalyst.

  • 16. Farkas, I.
    et al.
    Banyai, I.
    Szabo, Zoltan
    KTH, Tidigare Institutioner                               , Kemi.
    Wahlgren, U.
    Grenthe, I.
    Rates and mechanisms of water exchange of UO22+(aq) and UO2(oxalate)F(H2O)(2)(-): A variable-temperature O-17 and F-19 NMR study2000Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 39, nr 4, s. 799-805Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study consists of two parts: The first part comprised an experimental determination of the kinetic parameters for the exchange of water between UO2(H2O)(5)(2+) and bulk water, including an ab initio study at the SCF and MP2 levels of the geometry of UO2(H2O)(5)(2+), UO2(H2O)(4)(2+), and UO2(H2O)(6)(2+) and the thermodynamics of their reactions with water. In the second part we made an experimental study of the rate of water exchange in uranyl complexes and investigated how this might depend on inter- and intramolecular hydrogen bond interactions. The experimental studies, made by using O-17 NMR, with Tb3+ as a chemical shift reagent, gave the following kinetic parameters at 25 degrees C: k(ex) = (1.30 +/- 0.05) x 10(6) s(-1); Delta H double dagger = 26.(1) +/- 1.(4) kJ/mol; Delta S double dagger = -40 +/- 5 J/(K mol). Additional mechanistic indicators were obtained from the known coordination geometry of U(VI) complexes with unidentate ligands and from the theoretical calculations. A survey of the literature shows that there are no known isolated complexes of UO22+ with unidentate ligands which have a coordination number larger than 5. This was corroborated by quantum chemical calculations which showed that the energy gains by binding an additional water to UO2(H2O)(4)(2+) and UO2(H2O)(5)(2+) are 29.8 and -2.4 kcal/mol, respectively. A comparison of the change in Delta U for the reactions UO2(H2O)(5)(2+) --> UO2(H2O)(4)(2+) + H2O and UO2(H2O)(5)(2+) + H2O --> UO2(H2O)(6)(2+) indicates that the thermodynamics favors the second (associative) reaction in gas phase at 0 K, while the thermodynamics of water transfer between the first and second coordination spheres, UO2(H2O)(5)(2+) --> UO2(H2O)(4)(H2O)(2+) and UO2(H2O)(5)(H2O)(2+) --> UO2(H2O)(6)(2+), favors the first (dissociative) reaction. The energy difference between the associative and dissociative reactions is small, and solvation has to be included in ab initio models in order to allow quantitative comparisons between experimental data and theory. Theoretical calculations of the activation energy were not possible because of the excessive computing time required. On the basis of theoretical and experimental studies, we suggest that the water exchange in UO2(H2O)(5)(2+) follows a dissociative interchange mechanism. The rates of exchange of water in UO2(oxalate)F(H2O)(2-) (and UO2(oxalate)F-2(H2O)(2-) studied previously) are much slower than in the aquation, k(ex) = 1.6 x 10(4) s(-1), an effect which we assign to hydrogen bonding involving coordinated water and fluoride. The kinetic parameters for the exchange of water in UO2(H2O)(5)(2+) and quenching of photo excited *UO2(H2O)(5)(2+) are very near the same, indicating similar mechanisms.

  • 17.
    Farnum, Byron H.
    et al.
    Johns Hopkins University.
    Gardner, James M.
    Johns Hopkins University.
    Meyer, Gerald J.
    Johns Hopkins University.
    Flash-Quench Technique Employed To Study the One-Electron Reduction of Triiodide in Acetonitrile: Evidence for a Diiodide Reaction Product2010Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 49, nr 22, s. 10223-10225Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The one-electron reduction of triiodide (I3?) by a reduced ruthenium polypyridyl compound was studied in an acetonitrile solution with the flash-quench technique. Reductive quenching of the metal-to-ligand charge-transfer excited state of [RuII(deeb)3]2+ by iodide generated the reduced ruthenium compound [RuII(deeb?)(deeb)2]+ and diiodide (I2??). The subsequent reaction of [RuII(deeb?)(deeb)2]+ with I3? indicated that I2?? was a product that appeared with a second-order rate constant of (5.1 ± 0.2) ? 109 M?1 s?1. After correction for diffusion and some assumptions, Marcus theory predicted a formal potential of ?0.58 V (vs SCE) for the one-electron reduction of I3?. The relevance of this reaction to solar energy conversion is discussed.

  • 18. Gao, Weiming
    et al.
    Ekström, Jesper
    Liu, Jianhui
    Chen, Changneng
    Eriksson, Lars
    Weng, Linhong
    Åkermark, Björn
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Binuclear iron-sulfur complexes with bidentate phosphine ligands as active site models of Fe-hydrogenase and their catalytic proton reduction2007Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 46, nr 6, s. 1981-1991Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The displacement of CO in a few simple Fe(I)-Fe(I) hydrogenase model complexes by bisphosphine ligands Ph2P-(CH2)(n)-PPh2 [with n = 1 (dppm) or n = 2 (dppe)] is described. The reaction of [{mu-(SCH2)(2)CH2}Fe-2(CO)(6)] (1) and [{mu-(SCH2)(2)N(CH2CH2CH3)}Fe-2(CO)(6)] (2) with dppe gave double butterfly complexes [{mu-(SCH2)(2)CH2}Fe-2(CO)(5)(Ph2PCH2)](2) (3) and [{mu-(SCH2)(2)N(CH2CH2CH3)}Fe-2(CO)(5)(Ph2PCH2)](2) (4), where two Fe2S2 units are linked by the bisphosphine. In addition, an unexpected byproduct, [{mu-(SCH2)(2)N(CH2CH2CH3)}Fe-2(CO)(5){Ph2PCH2CH2(Ph2PS)}] (5), was isolated when 2 was used as a substrate, where only one phosphorus atom of dppe is coordinated, while the other has been converted to PS, presumably by nucleophilic attack on bridging sulfur. By contrast, the reaction of 1 and 2 with dppm under mild conditions gave only complexes [{mu-(SCH2)(2)CH2}Fe-2(CO)(5)(Ph2PCH2PPh2)] (6) and [{mu-(SCH2)(2)N(CH2CH2CH3)}Fe-2(CO)(5)(Ph2PCH2PPh2)] (8), where one ligand coordinated in a monodentate fashion to one Fe2S2 unit. Furthermore, under forcing conditions, the complexes [{mu-(SCH2)(2)CH2}Fe-2(CO)(4){mu-(Ph2P)(2)CH2}] (7) and [{mu-(SCH2)(2)N(CH2CH2CH3)}Fe-2(CO)(4){mu-(Ph2P)(2)CH2}] (9) were formed, where the phosphine acts as a bidentate ligand, binding to both the iron atoms in the same molecular unit. Electrochemical studies show that the complexes 3, 4, and 9 catalyze the reduction of protons to molecular hydrogen, with 4 electrolyzed already at -1.40 V versus Ag/AgNO3 (-1.0 V vs NHE).

  • 19. Gao, Weiming
    et al.
    Liu, Jianhui
    Akermark, Bjorn
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Bidentate phosphine ligand based Fe2S2-containing macromolecules: Synthesis, characterization, and catalytic electrochemical hydrogen production2006Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 45, nr 23, s. 9169-9171Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The reaction of [Fe-2(CO)(6)(mu-SCH2)(2)NCH2CH2N(mu-SCH2)(2)Fe-2(CO)(6)] (1) with 1,2-bis(diphenylphosphino) ethane in the presence of Me3NO, 2H(2)O affords two structurally different metallomacromolecules: a dimer of the type [{Fe-2(CO)(5)(mu-SCH2)(2)NCH2CH2N(mu-SCH2) Fe-2(2)(CO)(5)}(Ph2PCH2)(2)] (2) and a tetramer species containing eight iron centers with an overall formula of [{Fe-2(CO)(6)(mu-SCH2)(2)NCH2CH2N( mu-SCH2)(2)Fe-2(CO)(5)}(2)(Ph2PCH2)(2)] (3). Their structures have been determined by X-ray crystallography, showing one macrocyclic complex (2) and one linear complex (3). Electrochemical hydrogen evolution catalyzed by these two complexes with ca. 80-90 single-run turnovers is observed, indicating good potential as catalysts for future applications.

  • 20. Ghanem, R.
    et al.
    Xu, Y. H.
    Pan, J.
    Hoffmann, T.
    Andersson, J.
    Polivka, T.
    Pascher, T.
    Styring, S.
    Sun, Licheng C.
    Sundstrom, V.
    Light-driven tyrosine radical formation in a ruthenium-tyrosine complex attached to nanoparticle TiO22002Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 41, nr 24, s. 6258-6266Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We demonstrate a possibility of multistep electron transfer in a supramolecular complex adsorbed on the surface of nanocrystalline TiO2. The complex mimics the function of the tyrosinez and chlorophyll unit P-680 in natural photosystem II (PSII). A ruthenium(II) tris(bipyridyl) complex covalently linked to a L-tyrosine ethyl ester through an amide bond was attached to the surface of nanocrystalline TiO2 via carboxylic acid groups linked to the bpy ligands. Synthesis and characterization of this complex are described. Excitation (450 nm) of the complex promotes an electron to a metal-to-ligand charge-transfer (MLCT) excited state, from which the electron is injected into TiO2. The photogeneration of Ru(III) is followed by an intramolecular electron transfer from tyrosine to Ru(III), regenerating the photosensitizer Ru(II) and forming the tyrosyl radical. The tyrosyl radical is formed in less than 5 us with a yield of 15%. This rather low yield is a result of a fast back electron transfer reaction from the nanocrystalline TiO2 to the photogenerated Ru(III).

  • 21.
    Gorlov, Mikhail
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Pettersson, Henrik
    Hagfeldt, Anders
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Kloo, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Electrolytes for dye-sensitized solar cells based on interhalogen ionic salts and liquids2007Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 46, nr 9, s. 3566-3575Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we report on the preparation of interhalogen ionic liquids of the general formula [K+]XY2-, where K+ = 1,3-dialkylimidazolium, 1,2,3-trialkylimidazolium, or N-alkylpyridinium; XY2- = IBr2- or I2Br-. These compounds were characterized in solution and the solid state by NMR, IR, Raman, and mass spectroscopy. The crystal structure of the compound [Me(2)BuIm]IBr2 (7) shows that the IBr2- anion has a linear Br-I-Br structure. Indications of an equilibrium between different forms of XY2- anions in solution are observed. Interhalogen ionic salts and liquids were used as electrolyte components for encapsulated monolithic dye-sensitized solar cells. Overall light-to-electricity conversion efficiencies up to 6.4%, 5.0%, and 2.4% at 1000 W/m(2) were achieved by using electrolytes based on interhalogen ionic salts and gamma-butyrolactone, glutaronitrile, or native ionic liquids as solvents, respectively. Moreover, in terms of stability, the cell performance lost 9-14% of the initial performance after 1000 h illumination at 350 W/m(2).

  • 22. Gustafsson, Magnus
    et al.
    Fischer, Andreas
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Ilyukhin, Andrey
    Maliarik, Mikhail
    Nordblad, Per
    Novel Polynuclear Nickel(II) Complex: Hydrazine, Sulfato, and Hydroxo Bridging in an Unusual Metal Hexamer. Crystal Structure and Magnetic Properties of [Ni-6(N2H4)(6)(SO4)(4)(OH)(2)(H2O)(8)](SO4)(H2O)(10)2010Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 49, nr 12, s. 5359-5361Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A reaction between nickel(II) sulfate and hydrazine in aqueous solution yields blue crystals of [Ni-6(N2H4)(6)(SO4)(4)(OH)(2)(H2O)(8)] (SO4)(H2O)(10). The compound has been characterized by single, crystal and powder X-ray diffraction, vibrational spectroscopy, as well as variable-temperature magnetic susceptibility. This is the first reported crystal structure of the nickel(II) complex with hydrazine. The complex cation in the compound has a remarkable structure with unusual diversity of bridging groups including hydrazine molecules, sulfate ions, and hydroxo groups. Hydrazine molecules bridge nickel ions into trimers, which are further linked into hexamers through bridging sulfates. The magnetic susceptibility study of the compound reveals antiferromagnetic interaction between nickel(II) ions in the polynuclear complex.

  • 23.
    Hildebrandt, Lars
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Dinnebier, R.
    Jansen, M.
    Crystal structure and ionic conductivity of three polymorphic phases of rubidium trifluoromethyl sulfonate, RbSO3CF32006Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 45, nr 8, s. 3217-3223Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The crystal structures of three polymorphic phases of rubidium trifluoromethyl sulfonate (RbSO3CF3, rubidium 'triflate') were solved from X-ray powder diffraction data. At room temperature, rubidium triflate crystallizes in the monoclinic space group Cm with lattice parameters of a = 19.9611(5) angstrom, b = 23.49113(7) angstrom, c = 5.1514(2) angstrom, beta = 102.758(2)degrees; Z = 16. At T = 321 K, a first-order phase transition occurs toward a monoclinic phase in space group P2(1) with lattice parameters at T = 344 K of a = 10,3434(5) angstrom, b = 5.8283(3) angstrom, c = 5.1982(3) angstrom, beta = 104.278(6)degrees; Z = 2). At T = 461 K, another phase transition, this time of second order, occurs toward an orthorhombic phase in space group Cmcm with lattice parameters at T = 510 K of a = 5.3069(2) angstrom, b = 20.2423(10) angstrom, c = 5.9479(2) angstrom; Z = 4. As a common feature within all three crystal structures of rubidium triflate, the triflate anions are arranged in double layers with the lipophilic CF3 groups facing each other. The rubidium ions are located between the SO3 groups. The general packing is similar to the packing in cesium triflate. Rubidium triflate can be classified as a solid electrolyte with a specific ionic conductivity of sigma = 9.89 x 10(-9) S/cm at T = 384 K and sigma = 3.84 x 10(-6) S/cm at T = 481 K.

  • 24. Hjelm, J.
    et al.
    Handel, R. W.
    Hagfeldt, Anders
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Constable, E. C.
    Housecroft, C. E.
    Forster, R. J.
    Conducting polymers containing in-chain metal centers: Electropolymerization of oligothienyl-substituted {M(tpy)(2)} complexes and in situ conductivity studies, M = Os(II), Ru(II)2005Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 44, nr 4, s. 1073-1081Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The electropolymerization of a series of Ru and Os bis-terpyridine complexes that form rodlike polymers with bithienyl, quaterthienyl, or hexathienyl bridges has been studied. Absorption spectroscopy, scanning electron microscopy, and cyclic voltammetry have been used to characterize the monomers and resulting polymer films. The absolute dc conductivity of the quaterthienyl-bridged {Ru(tpy)(2)} and {Os(tpy)(2)} polymers is unusually large and independent of the identity of the metal center at 1.6 x 10(-3) S cm(-1). The maximum conductivity occurs at the formal potential of each redox process, which typically is observed for systems where redox conduction is the dominant charge transport mechanism. Significantly, the dc conductivity of the metal-based redox couple observed in these polymers is 2 orders of magnitude higher than that of a comparable nonconjugated system.

  • 25.
    Hopmann, Kathrin H.
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Guo, Jing-Dong
    Department of Applied Chemistry, Jiangxi Science and Technology Normal University.
    Himo, Fahmi
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Theoretical Investigation of the First-Shell Mechanism of Nitrile Hydratase2007Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 46, nr 12, s. 4850-4856Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The first-shell mechanism of nitrile hydratase (NHase) is investigated theoretically using density functional theory. NHases catalyze the conversion of nitriles to amides and are classified into two groups, the non-heme Fe(III) NHases and the non-corrinoid Co(III) NHases. The active site of the non-heme iron NHase comprises a low-spin iron (S = (1)/(2)) with a remarkable set of ligands, including two deprotonated backbone nitrogens and both cysteine-sulfenic and cysteine-sulfinic acids. A widely proposed reaction mechanism of NHase is the first-shell mechanism in which the nitrile substrate binds directly to the low-spin iron in the sixth coordination site. We have used quantum chemical models of the NHase active site to investigate this mechanism. We present potential energy profiles for the reaction and provide characterization of the intermediates and transition-state structures for the NHase-mediated conversion of acetonitrile. The results indicate that the first-shell ligand Cys114-SO- could be a possible base in the nitrile hydration mechanism, abstracting a proton from the nucleophilic water molecule. The generally suggested role of the Fe(III) center as a Lewis acid, activating the substrate toward nucleophilic attack, is shown to be unlikely. Instead, the metal is suggested to provide electrostatic stabilization to the anionic imidate intermediate, thereby lowering the reaction barrier.

  • 26. Jalilehvand, F.
    et al.
    Maliarik, M.
    Sandstrom, M.
    Mink, J.
    Persson, I.
    Persson, P.
    Toth, I.
    Glaser, Julius
    KTH, Tidigare Institutioner                               , Kemi.
    New class of oligonuclear platinum-thallium compounds with a direct metal-metal bond. 5. Structure determination of heterodimetallic cyano complexes in aqueous solution by EXAFS and vibrational spectroscopy2001Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 40, nr 16, s. 3889-3899Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The structures of three closely related heterodimetallic cyano complexes, [(NC)(5)Pt-Tl(CN)(n)](n-) (n = 1-3), formed in reactions between [Pt-II(CN)(4)](2-) and Tl-III cyano complexes, have been studied in aqueous solution. Multinuclear NMR data ((TI)-T-205, Pt-195, and C-13) were used for identification and quantitative analysis. X-ray absorption spectra were recorded at the Pt and TlLIII edges. The EXAFS data show, after developing a model describing the extensive multiple scattering within the linearly coordinated cyano ligands, short Pt-Tl bond distances in the [(NC)(5)Pt-Tl(CN)(n)](n-) complexes: 2.60(1), 2.62(1), and 2.64(1) Angstrom for n = 1-3, respectively. Thus, the Pt-Tl bond distance increases with increasing number of cyano ligands on the thallium atom. In all three complexes the thallium atom and five cyano ligands, with a mean Pt-C distance of 2.00-2.01 Angstrom, octahedrally coordinate the platinum atom. In the hydrated [(NC)(5)Pt-Tl(CN)(H2O)(4)](-) species the thallium atom coordinates one cyano ligand, probably as a linear Pt-TI-CN entity with a Tl-C bond distance of 2.13(1) Angstrom, and possibly four loosely bound water molecules with a mean Tl-O bond distance of about 2.51 Angstrom. In the [(NC)(5)Pt-Tl(CN)(2)](2-) species, the thallium atom probably coordinates the cyano ligands trigonally with two TI-C bond distances at 2.20(2) Angstrom, and in [(NC)(5)Pt-Tl(CN)(3)]Tl3- coordinates tetrahedrally with three TI-C distances at 2.22(2) Angstrom. EXAFS data were reevaluated for previously studied mononuclear thallium(III)-cyano complexes in aqueous solution, [Tl(CN)(2)(H2O)(4)](+), [Tl(CN)(3)(H2O)], and [Tl(CN)(4)](-), and also for the solid K[TI(CN)(4)] compound. A comparison shows that the TI-C bond distances are longer in the dinuclear complexes [(NC)(5)Pt-TI(CN)(n)](n-) (it = 1-3) for the same coordination number. Relative oxidation states of the metal atoms were estimated from their Pt-195 and (TI)-T-205 chemical shifts, confirming that the I(NC)5Pt-TI(CN),]n- complexes can be considered as metastable intermediates in a two-electron-transfer redox reaction from platinum(II) to thallium(III). Vibrational spectra were recorded and force constants from normal-coordinate analyses are used for discussing the delocalized bonding in these species.

  • 27. Johansson, A.
    et al.
    Abrahamsson, M.
    Magnuson, A.
    Huang, P.
    Martensson, J.
    Styring, S.
    Hammarstrom, L.
    Sun, Licheng C.
    Akermark, B.
    Synthesis and photophysics of one mononuclear Mn(III) and one dinuclear Mn(III,III) complex covalently linked to a ruthenium(II) tris(bipyridyl) complex2003Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 42, nr 23, s. 7502-7511Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The preparation of donor (D)-photosensitizer (S) arrays, consisting of a manganese complex as D and a ruthenium tris(bipyridyl) complex as S has been pursued. Two new ruthenium complexes containing coordinating sites for one (2a) and two manganese ions (3a) were prepared in order to provide models for the donor side of photosystem II in green plants. The manganese coordinating site consists of bridging and terminal phenolate as well as terminal pyridyl ligands. The corresponding ruthenium-manganese complexes, a manganese monomer 2b and dimer 3b, were obtained. For the dimer 3b, our data suggest that intramolecular electron transfer from manganese to photogenerated ruthenium(III) is fast, k(ET) > 5 x 10(7) s(-1).

  • 28.
    Johansson, Adam Johannes
    et al.
    Stockholm Univ, Dept Phys.
    Blomberg, M R A
    Siegbahn, P E M
    Density functional study of the O-2 binding to [Cu-I(TPA(R))](+) (TPA = tris(2-pyridyimethyl)amine) in THF and EtCN2006Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 45, nr 4, s. 1491-1497Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Density functional theory using the B3LYP hybrid functional has been employed to study the formation of [Cu-II(TPA(H))(O-2(-))](+) and [Cu-II(TPA(MeO))(O-2(-))](+) (TPA = tris(2-pyridylmethyl)amine) in two different solvents, THF and EtCN. The thermodynamics of solvent coordination as well as that of the overall reactions with O-2 has been computed. The formations of [Cu-II(TPA(H))(O-2(-))](+) in THF and of [Cu-II(TPA(MeO))(O-2(-))](+) in both THF and EtCN are found to be initiated from the [Cu-I(TPAR)]+ species, that is, the Cu complex possessing an empty coordination site. In contrast, the formation of [Cu-II(TPA(H))(O-2(-))](+) in EtCN is found to be initiated from the [Cu-I(TPA(H))(EtCN)](+) species, that is, one solvent molecule being coordinated to Cui. In general, good agreement is found between theoretical and experimental results. The high accuracy of the B3LYP functional in reproducing experimental thermodynamic data for the present type of transition metal complexes is demonstrated by the fact that the differences between measured and computed thermodynamic parameters (Delta G degrees, Delta H degrees, and -T Delta S degrees, in most cases are less than 2.0 kcal mol(-1). An attempt was made to investigate the kinetics of the formation of [Cu-II(TPA(H))(O-2(-))](+) in THF and EtCN. Computed free energies of activation, Delta G(double dagger), are in good agreement with experimental results. However, an analysis of the partitioning of the free energy barriers in enthalpic and entropic contributions indicates that the computationally studied reaction pathway might differ from the one observed experimentally.

  • 29. Johansson, O.
    et al.
    Borgstrom, M.
    Lomoth, R.
    Palmblad, M.
    Bergquist, J.
    Hammarstrom, L.
    Sun, Licheng C.
    Akermark, B.
    Electron donor-acceptor dyads based on ruthenium(II) bipyridine and terpyridine complexes bound to naphthalenediimide2003Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 42, nr 9, s. 2908-2918Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two series of photosensitizer-electron acceptor complexes have been synthesized and fully characterized: ruthenium(11) tris(bipyridine) {[Ru-II(bpy)(2)(bpy-X-NDI)], where X = -CH2-, tolylene, or phenylene, bpy is 2,2'-bipyridine, and NDI is naphthalenediimide} and ruthenium(II) bis(terpyridine) {[Ru-II(Y-tpy)(tpy-X-NDI)], where Y = H or tolyl and X = tolylene or phenylene, and tpy = 2,2':6',2-terpyridine}. The complexes have been studied by cyclic and differential pulse voltammetry and by steady state and time-resolved absorption and emission techniques. Rates for forward and backward electron transfer have been investigated, following photoexcitation of the ruthenium(II) polypyridine moiety. The terpyridine complexes were only marginally affected by the linked diimide unit, and no electron transfer was observed. In the bipyridine complexes we achieved efficient charge separation. For the complexes containing a phenyl link between the ruthenium(II) and diimide moieties, our results suggest a biphasic forward electron-transfer reaction, in which 20% of the charge-separated state was formed via population of the naphthalenediimide triplet state.

  • 30. Joszai, R.
    et al.
    Beszeda, I.
    Benyei, A. C.
    Fischer, Andreas
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Kovacs, M.
    Maliarik, M.
    Nagy, P.
    Shchukarev, A.
    Toth, I.
    Metal-metal bond or isolated metal centers? Interaction of Hg(CN)(2) with square planar transition metal cyanides2005Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 44, nr 26, s. 9643-9651Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Three adducts have been prepared from Hg(CN)(2) and square planar M-II(CN)(4)(2-) transition metal cyanides (M = Pt, Pd, or Ni, with d(8) electron shell) as solids. The structure of the compounds K2PtHg(CN)(6)center dot 2H(2)O (1), Na2PdHg(CN)(6)center dot 2H(2)O (2), and K2NiHg(CN)(6)center dot 2H(2)O (3) have been studied by single-crystal X-ray diffraction, XPS, Raman spectroscopy, and luminescence spectroscopy in the solid state. The structure of K2PtHg(CN)(6)center dot 2H(2)O consists of one-dimensional wires. No CN- bridges occur between the heterometallic centers. The wires are strictly linear, and the Pt(II) and Hg(II) centers alternate. The distance d(Hg-Pt) is relatively short, 3.460 angstrom. Time-resolved luminescence spectra indicate that Hg(CN)2 units incorporated into the structure act as electron traps and shorten the lifetime of both the short-lived and longer-lived exited states in 1 compared to K-2[Pt(CN)(4)]center dot 2H(2)O. The structures of Na2PdHg(CN)(6)center dot 2H(2)O and K2NiHg(CN)(6)center dot 2H(2)O can be considered as double salts; the lack of heterometallophilic interaction between the remote Hg(II) and Pd(II) atoms, d(Hg-Pd) = 4.92 angstrom, and Hg(II) and Ni(II) atoms, d(Hg-Ni) = 4.61 angstrom, is apparent. Electron binding energy values of the metallic centers measured by XPS show that there is no electron transfer between the metal ions in the three adducts. In solution, experimental findings clearly indicate the lack of metal-metal bond formation in all studied Hg-II-CN--M-II(CN)(4)(2-) systems (M = Pt, Pd, or Ni).

  • 31. Khoshtariya, D. E.
    et al.
    Dolidze, T. D.
    Zusman, L. D.
    Lindbergh, Göran
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Glaser, Julius
    KTH, Tidigare Institutioner                               , Kemi.
    Two-electron transfer for Tl(aq)(3+)/Tl(aq)(+) revisited. Common virtual Tl-II-Tl-III (4+) intermediate for homogeneous (superexchange) and electrode (sequential) mechanisms2002Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 41, nr 7, s. 1728-1738Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Homogeneous and electrochemical two-electron transfers within the TI(aq)(3+)/TI(aq)(+) couple are considered on a common conceptual basis. For the 2 equiv electrochemical reduction of TI(aq)(3) to TI(aq)(+), the intermediate state with a formal reduction potential, E-1* = 1.04 +/- 0.10 V vs the normal hydrogen electrode, was detected, different from the established value of 0.33 V for a TI3+/TI2+ couple. Examination of obtained electrochemical (cyclic voltammetry (CV) and rotating disk electrode techniques, along with the CV-curve computer simulation procedure) and literature data indicate that the detected formal potential cannot be the property of electrode-adsorbed species, but rather of the covalently interacting dithallium intermediate [TI11-TI11](4+) located at the outer Helmholtz plane. The analysis of microscopic mechanisms, based on the recent hypothesis of H. Taube and the Marcus-Hush theory extended by Zusman and Beratan, and Koper and Schmickler, revealed that the homogeneous process most probably takes place through the superexchange inner-sphere two-electron-transfer mechanism, via an essentially virtual (undetectable) dithallium intermediate. In contrast, the electrochemical process occurs through a sequential mechanism, via the rate-determining step of TI(aq)(2+) ion formation immediately followed by activationless formation of the metastable (CV-active) dithallium state. The second electrochemical electron-transfer step is fast, and shows up only in the peak height (but not in the shape) of the observed CV cathodic wave, The anodic wave for a microscopically reverse process of the oxidation of TI(aq)(+) to TI(aq)(3+) cannot be observed within the considered potential range due to the blocking of through-space electron transfer by the competitor process of ion transfer to the electrode.

  • 32. Kopylovich, M. N.
    et al.
    Pombeiro, A. J. L.
    Fischer, Andreas
    KTH, Tidigare Institutioner                               , Kemi.
    Kloo, Lars A.
    KTH, Tidigare Institutioner                               , Kemi.
    Kukushkin, V. Y.
    Facile Ni(II)/ketoxime-mediated conversion of organonitriles into imidoylamidine ligands. Synthesis of imidoylamidines and acetyl amides2003Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 42, nr 22, s. 7239-7248Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Treatment of alkyl nitriles with NiX2.6H(2)O (X = Cl, NO3) and 2-propanone oxime, followed by (X = Cl) addition of [i-Pr4N](NO3) for precipitation of the product, resulted in the formation of amidinium nitrates [RC(=NH2)NH2](NO3) (R = Me, Et, n-Pr), The reaction went to another direction with NiX2.2H(2)O, i.e., the reaction between neat RCN (R = Me, Et, n-Pr, i-Pr, n-Bu, CH2Cl, CH2C6H4OMe-p) and NiCl2.2H(2)O/2-propanone oxime (other ketoximes can also be used) gave the (imidoylamidine)Ni(II) complexes [Ni{(N) under bar (H)=C(R)NHC(R)=(N) under barH}(2)](2+) (1(2+)-7(2+)). The latter were isolated in good yields (65-91%) as the bis-chloride salts 1.Cl-2-6.Cl-2 and the mixed salt 7.(Cl)(p-MeOC6H4CH2CO2). Remarkably, the latter transformation does not proceed at all if NiCl2.2H(2)O or the ketoxime are taken alone. Liberation of imidoylamidines was performed for one alkyl-containing complex [2.Cl-2] and one benzyl-containing complex [7.(Cl)(p-MeOC6H4CH2CO2)], by (i) addition of HBF4.Et2O to the acetonitrile solution of the complexes to yield [N(H)=C(R)NHC(R)=NH].2HBF(4) (R = Et 8 and R = CH2C6H4OMe-p 9) or (ii) substitution for ethanediamine (en) with following precipitation of the complex [Ni(en)(3)]Cl-2 with formation of free N(H) C(R)NHC(R)=NH (R = Et 10 and R = CH2C6H4OMe-p 11). In contrast to the liberation in nonaqueous media, treatment of 2.Cl-2 and 7.(CI)(P-MeOC6H4CH2CO2) with Na(2)EDTA.2H(2)O in water-methanol solutions led to substitution and hydrolysis to furnish the acyl amides {EtC(=O)} 2NH (12) and {p-MeOC6H4CH2C(=0)}(2)NH (13). Alternatively, 12 and 13 were obtained by hydrolysis of 10 and 11 in water at pH ca. 8.5. It was shown that the oxime complexes trans-[NiCl2(C4H8C=NOH)(4)] (14) or cis-[Ni(O,O-NO3)(2)(C4H8C=NOH)(2)] (15) can be intermediates in the formation of amidines and imidoylamidines. The sequence of the Ni(II)/oxime mediated formation of (imidoylamidine)Ni complexes and liberation (or hydrolytic liberation) of the ligands opens up a novel, facile and environmentally benign route to imidoylamidines and acyl amides.

  • 33.
    Kärkäs, Markus D.
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Organisk kemi.
    Li, Ying-Ying
    Huazhong Univ Sci & Technol, Sch Chem & Chem Engn, Key Lab Mat Chem Energy Convers & Storage, Hubei Key Lab Mat Chem & Serv Failure,Minist Educ, Wuhan 430074, Hubei, Peoples R China..
    Siegbahn, Per E. M.
    Stockholm Univ, Dept Organ Chem, Arrhenius Lab, SE-10691 Stockholm, Sweden..
    Liao, Rong-Zhen
    Huazhong Univ Sci & Technol, Sch Chem & Chem Engn, Key Lab Mat Chem Energy Convers & Storage, Hubei Key Lab Mat Chem & Serv Failure,Minist Educ, Wuhan 430074, Hubei, Peoples R China..
    Åkermark, Björn
    Stockholm Univ, Dept Organ Chem, Arrhenius Lab, SE-10691 Stockholm, Sweden..
    Metal-Ligand Cooperation in Single-Site Ruthenium Water Oxidation Catalysts: A Combined Experimental and Quantum Chemical Approach2018Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 57, nr 17, s. 10881-10895Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Catalysts for oxidation of water to molecular oxygen are essential in solar-driven water splitting. In order to develop more efficient catalysts for this oxidatively demanding reaction, it is vital to have mechanistic insight in order to understand how the catalysts operate. Herein, we report the mechanistic details associated with the two Ru catalysts 1 and 2. Insight into the mechanistic landscape of water oxidation catalyzed by the two single-site Ru catalysts was revealed by the use of a combination of experimental techniques and quantum chemical calculations. On the basis of the obtained results, detailed mechanisms for oxidation of water by complexes 1 and 2 are proposed. Although the two complexes are structurally related, two deviating mechanistic scenarios are proposed with metal-ligand cooperation being an important feature in both processes. The proposed mechanistic platforms provide insight for the activation of water or related small molecules through nontraditional and previously unexplored routes.

  • 34.
    Leandri, Valentina
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Daniel, Quentin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Organisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Chen, Hong
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Organisk kemi.
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Organisk kemi.
    Gardner, James M.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Kloo, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Electronic and Structural Effects of Inner Sphere Coordination of Chloride to a Homoleptic Copper(II) Diimine Complex2018Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 57, nr 8, s. 4556-4562Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The reaction of CuCl2 with 2,9-dimethyl-1,10-phenanthroline (dmp) does not lead to the formation of [Cu(dmp)(2)](Cl)(2) but instead to [Cu(dmp)(2)Cl]Cl, a 5-coordinated complex, in which one chloride is directly coordinated to the metal center. Attempts at removing the coordinated chloride by changing the counterion by metathesis were unsuccessful and resulted only in the exchange of the noncoordinated chloride, as confirmed from a crystal structure analysis. Complex [Cu-(dmp)(2)Cl]PF6 exhibits a reversible cyclic voltammogram characterized by a significant peak splitting between the reductive and oxidative waves (0.85 and 0.60 V vs NHE, respectively), with a half-wave potential E-1/2 = 0.73 V vs NHE. When reduced electrochemically, the complex does not convert into [Cu(dmp)(2)](+), as one may expect. Instead, [Cu(dmp)(2)](+) is isolated as a product when the reduction of [Cu(dmp)(2)Cl]PF6 is performed with L-ascorbic acid, as confirmed by electrochemistry, NMR spectroscopy, and diffractometry. [Cu(dmp)(2)](2+) complexes can be synthesized starting from Cu(II) salts with weakly and noncoordinating counterions, such as perchlorate. Growth of [Cu(dmp)(2)](ClO4)(2) crystals in acetonitrile results in a 5-coordinated complex, [Cu(dmp)(2)(CH3CN)](ClO4)(2), in which a solvent molecule is coordinated to the metal center. However, solvent coordination is associated with a dynamic decoordination-coordination behavior upon reduction and oxidation. Hence, the cyclic voltammogram of [Cu(dmp)(2)(CH3CN)](2+) is identical to the one of [Cu(dmp)(2)](+), if the measurements are performed in acetonitrile. The current results show that halide ions in precursors to Cu(II) metal-organic coordination compound synthesis, and most likely also other multivalent coordination centers, are not readily exchanged when exposed to presumed strongly binding and chelating ligand, and thus special care needs to be taken with respect to product characterization.

  • 35. Li, Fei
    et al.
    Wang, Mei
    Li, Ping
    Zhang, Tingting
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Iron(III) complexes with a tripodal N3O ligand containing an internal base as a model for catechol intradiol-cleaving dioxygenases2007Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 46, nr 22, s. 9364-9371Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A bis(mu-alkoxo)-bridged dinuclear iron(III) complex [Fe(L)(NO3)](2)(NO3)(2) [1; HL = NN-bis(2-pyridylmethyl)-N-(2hydroxyethyl)amine] of the tripodal N3O ligand was prepared as a biomimetic model for the intradiol-cleaving dioxygenase enzymes. The reaction of 1 and catechol in the presence of excess triethylamine gave the catecholate (CAT) chelate b is(u -al koxo) -bridged dinuclear iron(Ill) complex [Fe(L)(CAT)12 (2). The molecular structures of complexes 1 and 2 were determined by X-ray crystallography. Diiron complexes 1 and 2 contain the same bis(u-alkoxo)diiron diamond core. All heteroatoms (N3O) of the ligand are coordinated to the iron center in complex 1 with two pyridine nitrogen atoms on the axial bonds, while one of the pyridyl arms of the ligand is left uncoordinated in complex 2. The interaction of the diiron complex 1 and 3,5-di-tert-butylcatechol (H2DBC) was investigated by electronic and mass spectroscopy. Complex 1 displays the intradiol-cleaving dioxygenase activity, and the coordinate ethoxyl arm of the ligand is capable of accepting the proton from catechol, which mimics the function of Tyr447 in the. protocatechuate 3,4-dioxygenase as an internal base. The spectrop h oto metric titration experiment indicates the relatively low demand of the external base (0.8 equiv based on Fe3+) for attaining the highest dioxygenase activity of complex 1. The reaction rate of the reactive intermediate [Fe(HL)(DBC)](+) with dioxygen is 0.38 M-1 s(-1) determined by kinetic studies.

  • 36.
    Li, Yunguo
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Lousada, Claudio Miguel
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Soroka, Inna L.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Bond Network Topology and Antiferroelectric Order in Cuprice CuOH2015Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 54, nr 18, s. 8969-8977Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Using density functional theory (DFT) and a graph theory based approach, we investigated the topology of bond network in CuOH(s) (cuprice) considering only symmetry-distinct structures. In parallel, we conducted the synthesis and X-ray diffraction characterization of the compound and used the combined theoretical-experimental effort to validate the lowest energy structure obtained with DFT. The ground-state structure of CuOH(s) consists of compact trilayers of CuOH connected to each other via hydrogen bonds, where the inner layer of each trilayer is composed entirely of Cu atoms. Each trilayer is a dense fabric made of two interlocked arrays of polymer [CuOH]<inf>n</inf> chains. This structure corresponds to an antiferroelectric configuration where the dipole moments of CuOH molecules belonging to adjacent arrays are antiparallel and are arranged in the same way as the water molecules in ice-VIII. It is shown that a collective electrostatic interaction is the main driving force for the cation ordering while the local atomic configuration is maintained. These findings and the possibility of synthesizing exfoliated two-dimensional cuprice are important for some technological applications.

  • 37.
    Liao, Rong-Zhen
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Yu, Jian-Guo
    Himo, Fahmi
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Reaction mechanism of the dinuclear zinc enzyme N-acyl-L-homoserine lactone hydrolase: a quantum chemical study2009Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 48, nr 4, s. 1442-1448Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    N-acyl-L-homoserine lactone hydrolase (AHL lactonase) is a dinuclear zinc enzyme responsible for the hydrolytic ring opening of AHLs, disrupting quorum sensing in bacteria. The reaction mechanism is investigated using hybrid density functional theory. A model of the active site is designed on the basis of the X-ray crystal structure, and stationary points along the reaction pathway are optimized and analyzed. Two possible mechanisms based on two different substrate orientations are considered. The calculations give support to a reaction mechanism that involves two major chemical steps: nucleophilic attack on the substrate carbonyl carbon by the bridging hydroxide and ring opening by direct ester C - O bond cleavage. The roles of the two zinc ions are analyzed. Zn1 is demonstrated to stabilize the charge of the tetrahedral intermediate, thereby facilitating the nucleophilic attack, while Zn2 stabilizes the charge of the alkoxide resulting from the ring opening, thereby lowering the barrier for the C - O bond cleavage.

  • 38. Ma, G. B.
    et al.
    Molla-Abbassi, A.
    Kritikos, M.
    Ilyukhin, A.
    Jalilehvand, F.
    Kessler, V.
    Skripkin, M.
    Sandstrom, M.
    Glaser, Julius
    KTH, Tidigare Institutioner                               , Kemi.
    Naslund, J.
    Persson, I.
    Structure of the dimethyl sulfoxide solvated thallium(III) ion in solution and in the solid state2001Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 40, nr 25, s. 6432-6438Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The structure and vibrational spectra of the dimethyl sulfoxide solvated thallium(III) ion have been studied in a dimethyl sulfoxide solution and in the solid state. X-ray crystallography shows a trigonal unit cell, space group R (3) over bar (No. 148), for the [TI(dmso)(6)](ClO4)(3) Compound with Z = 3, a = b = 11.9764(13) [11.8995(9)] Angstrom, c = 20.802(2) [20.467(2)] Angstrom, and V = 2584.0(5) [2509.9(4)] Angstrom (3) at 295 [150] K. The crystal structure comprises a highly symmetric hexakis(dimethyl sulfoxide)thallium(III) ion, with thallium in a 3 symmetry site and a TI-O bond distance of 2.224(3) Angstrom at 295 K. The octahedral TlO6 kernel is compressed along the threefold axis with an O-Tl-O bond angle of 96.20(11)degrees. The Tl-O-S bond angle of 120.7(2)degrees corresponds to a Tl . . .S distance of 3.292(2) Angstrom. One perchlorate ion centered on the (3) over bar axis was described by a statistically disordered model. A low-temperature EXAFS study (10 K) resulted in the TI-O and Tl . . .S distances of 2.221(4) and 3.282(6) Angstrom, respectively, consistent with a Tl-O-S bond angle of 120(1)degrees. The low Debye-Waller factors confirm a regular coordination without the disorder of the dimethyl sulfoxide ligands, which would have resulted from the alternative choice of space group R3 for the crystal structure. Raman and infrared spectra have been recorded and assigned, with the bands at 435 and 447 cm(-1) corresponding to the vibrational frequency of the symmetric and asymmetric TI-O stretching modes, respectively. EXAFS data of a 0.5 mol dm(-3) thallium(III) trifluoromethanesulfonate in a dimethyl sulfoxide solution were consistent with that of a hexasolvated ion with mean Tl-O and Tl . . .S distances of 2.22(1) and 3.33(2) Angstrom, respectively, which correspond to a mean Tl-O-S bond angle of 124(2)degrees. The anomalously large disorder parameter for the TI-O distances is consistent with a weal, pseudo-Jahn-Teller effect. The Tl-205, C-13, and H-1 NMR spectra of the complex in solution show single signals at 1886, 39.5, and 2.3 ppm, respectively.

  • 39.
    Ma, Gui-Bin
    et al.
    KTH, Tidigare Institutioner, Kemi.
    Kritikos, M.
    Maliarik, Mikhail
    KTH, Tidigare Institutioner, Kemi.
    Glaser, Julius
    KTH, Tidigare Institutioner, Kemi.
    Modification of binuclear Pt-Tl bonded complexes by attaching bipyridine ligands to the thallium site2004Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 43, nr 14, s. 4328-4340Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Complex formation of monomeric thallium(III) species with 2,2'-bipyridine (bipy) in dimethyl sulfoxide (dmso) and acetonitrile solutions was studied by means of multinuclear (H-1, C-13, and (TI)-T-205) NMR spectroscopy. For the first time, NMR signals of the individual species [TI(bipy)(m)(SoIV)](3+) (M = 1-3) were observed despite intensive ligand and solvent exchange processes. The tris(bipy) complex was crystallized as [TI(biPY)(3)(dmso)](ClO4)(3)(dMSO)(2) (1), and its crystal structure determined. In this compound, thallium is seven-coordinated; it is bonded to six nitrogen atoms of the three bipy molecules and to an oxygen atom of dmso. Metal-metal bonded binuclear complexes [(NC)(5)Pt-TI(CN)(n)(SoIV)](n-) (n = 0-3) have been modified by attaching bipy molecules to the thallium atom. A reaction between [(NC)(5)Pt-TI(dMSO)(4)](s) and 2,2'-bipyridine in dimethyl sulfoxide solution results in the formation of a new complex, [(NC)(5)Pt-TI(bipy)(solv)]. The presence of a direct Pt-TI bond in the complex is convincingly confirmed by a very strong one-bond Pt-195-(TI)-T-205 spin-spin coupling ((1)J((195)pt-(TI)-T-205) = 64.9 kHz) detected in both Pt-195 and (TI)-T-205 NMR spectra. In solutions containing free cyanide, coordination of CN- to the thallium atom occurs, and the complex [(NC)(5)Pt-TI(bipy)(CN)(solv)](-) ((1)J(Pt-195-(TI)-T-205) = 50.1 kHz) is formed as well. Two metal-metal bonded compounds containing bipy as a ligand were crystallized and their structures determined by X-ray diffractometry: [(NC)(5)Pt-TI(bipy)(dMSO)(3)] (2) and [(NC)(5)Pt-TI(biPY)(2)] (3). The Pt-TI bonding distances in the compounds, 2.6187(7) and 2.6117(5) Angstrom, respectively, are among the shortest reported separations between these two metals. The corresponding force constants in the molecules, 1.38 and 1.68 N/cm, respectively, were calculated using Raman stretching frequencies of the Pt-TI vibrations and are characteristic for a single metal-metal bond. Electronic absorption spectra were recorded for the [(NC)(5)Pt-TI(bipy)(m)(solv)] compounds, and the optical transition was attributed to the metal-metal bond assigned.

  • 40. Maliarik, Mikhail
    et al.
    Nagle, Jeffrey K.
    Ilyukhin, Andrey
    Murashova, Elena
    Mink, Janos
    Skripkin, Mikhail
    Glaser, Julius
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Kovacs, Margit
    Horvath, Attila
    Metal-metal bonding in tetracyanometalates (M = Pt-II, Pd-II, Ni-II) of monovalent thallium. Crystallographic and spectroscopic characterization of the new compounds Tl2Ni(CN)(4) and Tl2Pd(CN)(4)2007Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 46, nr 11, s. 4642-4653Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The new crystalline compounds Tl2Ni(CN)(4) and Tl2Pd(CN)(4) were synthesized by several procedures. The structures of the compounds were determined by single-crystal X-ray diffraction. The compounds are isostructural with the previously reported platinum analogue, Tl2Pt(CN)(4). A new synthetic route to the latter compound is also suggested. In contrast to the usual infinite columnar stacking of [M(CN)(4)](2-) ions with short intrachain M-M separations, characteristic of salts of tetracyanometalates of Ni-II, Pd-II, and Pt-II, the structure of the thallium compounds is noncolumnar with the two Tl-I ions occupying axial vertices of a distorted pseudo-octahedron of the transition metal, [MTl2C4]. The Tl-M distances in the compounds are 3.0560(6), 3.1733(7), and 3.140(1) A for Ni-II, Pd-II, and Pt-II, respectively. The short Tl-Ni distance in Tl2Ni(CN)(4) is the first example of metal-metal bonding between these two metals. The strength of the metal-metal bonds in this series of compounds was assessed by means of vibrational spectroscopy. Rigorous calculations, performed on the molecules in D-4h point group symmetry, provide force constants for the Tl-M stretching vibration constants of 146.2, 139.6, and 156.2 N/m for the Ni-II, Pd-II, and Pt-II compounds, respectively, showing the strongest metal-metal bonding in the case of the Tl-Pt compound. Amsterdam density-functional calculations for isolated Tl2M(CN)(4) molecules give Tl-M geometry-optimized distances of 2.67, 2.80, and 2.84 A for M = Ni-II, Pd-II, and Pt-II, respectively. These distances are all substantially shorter than the experimental values, most likely because of intermolecular Tl-N interactions in the solid compounds. Time-dependent density-functional theory calculations reveal a low-energy, allowed transition in all three compounds that involves excitation from an a(1g) orbital of mixed Tl 6p(z)-M nd(z)(2) character to an a(2u) orbital of dominant Tl 6p(z) character.

  • 41.
    Merenyi, Gabor
    et al.
    KTH, Tidigare Institutioner                               , Kemi.
    Lind, Johan
    KTH, Tidigare Institutioner                               , Kemi.
    Czapski, G.
    Goldstein, S.
    Direct determination of the Gibbs' energy of formation of peroxynitrous acid2003Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 42, nr 12, s. 3796-3800Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The kinetics of decomposition of peroxynitrous acid (ONOOH) was investigated in the presence of 0.1-0.75 M HClO4 and at a constant ionic strength. The decay rate of ONOOH decreased in the presence of H2O2, approaching a limiting value well below 75 mM H2O2. It also decreased in the presence of relatively low [HNO2] but did not approach a lower limiting value, since ONOOH reacts directly with HNO2. The latter reaction corresponds to a HNO2- and H+-catalyzed isomerization of ONOOH to nitrate, and its third-order rate constant was determined to be 520 +/- 30 M-2 s(-1). The mechanism of formation of O2NOOH from ONOOH in the presence of H2O2 was also scrutinized. The results demonstrated that in the presence of 0.1-0.75 M HClO4 and 75 mM H2O2 the formation Of O2NOOH is insignificant. The most important finding in this work is the reversibility of the reaction ONOOH + H2O reversible arrow HNO2 + H2O2, and its equilibrium constant was determined to be (7.5 +/- 0.4) x 10(-4) M. Using this value, the Gibbs' energy of formation of ONOOH was calculated to be 7.1 +/- 0.2 kcal/mol. This figure is in good agreement with the value determined previously from kinetic data using parameters for radicals formed during homolysis of peroxynitrite.

  • 42. Mizuoka, K
    et al.
    Grenthe, Ingmar
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Ikeda, Y
    Structural and kinetic studies on uranyl(V) carbonate complex using C-13 NMR spectroscopy2005Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 44, nr 13, s. 4472-4474Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have measured C-13 NMR spectra of uranyl(V) carbonate complex in D2O solution containing 1.003 M Na-2 (CO3)-C-13 at various temperatures. Two singlet signals corresponding to free and coordinated CO32- were observed at 169.13 and 106.70 ppm, respectively. From the peak area ratio, the structure of the uranyl(V) carbonate complex was determined as [(UO2)-O-V(CO3)(3)](5-). Furthermore, kinetic analyses of the exchange reaction of free and coordinated CO32- in [(UO2)-O-V(CO3)(3)](5-) were carried out using 13C NMR line-broadening. As a result, the first-order rate constant at 298 K and the activation parameters for CO32- exchange reaction in [(UO2)-O-V(CO3)(3)](5-) were evaluated as 1.13 x 10(3) s(-1) and Delta H-not equal = 62.0 +/- 0.7 KJ(.)mol(-1), Delta S-not equal = 22 +/- 3 J(.)mol(-1.)K(-1), respectively. We suggest that the exchange follows a dissociative mechanism as in the corresponding [(UO2)-O-VI(CO3)(3)](4-) complex.

  • 43. Na, Yong
    et al.
    Pan, Jingxi
    Wang, Mei
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Intermolecular electron transfer from photogenerated Ru(bpy)(3)(+) to 2Fe2S model complexes of the iron-only hydrogenase active site2007Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 46, nr 10, s. 3813-3815Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Visible light-driven intermolecular electron transfer was observed from a reduced species Ru(bpy)(3)(+), photogenerated via a reductive quenching of the ruthenium photosensitizer by a diethyldithiocarbamate anion, to bioinspired [2Fe2S] model complexes of the iron-only hydrogenase active site. The results indicate that Ru(bpy)(3)(2+) can act as a photoactive functional model of the [4Fe4S] cluster, playing the role of an electron-transfer relay. The photogenerated (FeFe0)-Fe-I species, which is proposed to be a crucial intermediate for proton reduction catalyzed electrochemically by the [2Fe2S] complexes, gives promise in the light-driven dihydrogen evolution using diiron complexes as surrogates of noble platinum catalysts.

  • 44. Na, Yong
    et al.
    Wang, Mei
    Pan, Jingxi
    Zhang, Pan
    Akermark, Bjoern
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Visible light-driven electron transfer and hydrogen generation catalyzed by bioinspired 2Fe2S complexes2008Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 47, nr 7, s. 2805-2810Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Complexes [{(mu-SCH2)(2)NCH2C6H5){Fe(CO)(2)L-1){Fe(CO)(2)L-2}] (L-1 = CO, L-2 = P(Pyr)(3), 2; L-1 = L-2 = P(Pyr)(3), 3) were prepared, which have the lowest reduction potentials for the mono- and double-CO-displaced diiron complexes reported so far. Hydrogen evolution, driven by visible light, was successfully observed for a three-component system, consisting of a ruthenium polypyridine complex, the biomimetic model complex 2 or 3, and ascorbic acid as both electron and proton donor in CH3CN/H2O. The electron transfer from photogenerated Ru(bPY)(3)(+) to 2 or 3 was detected by laser flash photolysis. Under optimal conditions, the total turnover number for hydrogen evolution was 4.3 based on 2 and 86 based on Ru(bPY)(3)(2+) in a three-hour photolysis.

  • 45. Nagy, P.
    et al.
    Fischer, Andreas
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Glaser, Julius
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Ilyukhin, A.
    Maliarik, M.
    Toth, I.
    Solubility, complex formation, and redox reactions in the Tl2O3-HCN/CN--H2O system. Crystal structures of the cyano compounds Tl(CN)(3)center dot H2O, Na Tl(CN)(4) center dot 3H(2)O, K Tl(CN)41, and Tl-I Tl-III(CN)41 and of (Tl2C2O4)-C-I2005Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 44, nr 7, s. 2347-2357Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thallium(III) oxide can be dissolved in water in the presence of strongly complexing cyanide ions. TI111 is leached from its oxide both by aqueous solutions of hydrogen cyanide and by alkali-metal cyanides. The dominating cyano complex of thallium(III) obtained by dissolution of TI2O3 in HCN is [TI(CN)(3)(aq)] as shown by (TI)-T-205 NMR. The TI(CN)(3) species has been selectively extracted into diethyl ether from aqueous solution with the ratio CN-/TI111 = 3. When aqueous solutions of the MCN (M = Na+, K+) salts are used to dissolve thallium(III) oxide, the equilibrium in liquid phase is fully shifted to the [TI(CN)(4)](-) complex. The TI(CN)(3) and TI(CN)(4)(-) species have for the first time been synthesized in the solid state as TI(CN)(3)(H2O)-H-. (1), M[TI(CN)(4)] (M = TI (2) and K (3)), and Na[TI(CN)(4)](.)3H(2)O (4) salts, and their structures have been determined by single-crystal X-ray diffraction. In the crystal structure of 1, the thallium(III) ion has a trigonal bipyramidal coordination with three cyanide ions in the equatorial plane, while an oxygen atom of the water molecule and a nitrogen atom from a cyanide ligand, attached to a neighboring thallium complex, form a linear O-TI-N fragment. In the three compounds of the tetracyano-thallium(III) complex, 2-4, the [TI(CN)(4)](-) unit has a distorted tetrahedral geometry. Along with the acidic leaching (enhanced by TI111-CN- complex formation), an effective reductive dissolution of the thallium(III) oxide can also take place in the TI2O3-HCN-H2O system yielding thallium(l), while hydrogen cyanide is oxidized to cyanogen. The latter is hydrolyzed in aqueous solution giving rise to a number of products including (CONH2)(2), NCO-, and NH4+ detected by N-14 NMR. The crystalline compounds, TI1[TI111(CN)(4)], (TI2C2O4)-C-1, and (CONH2)(2), have been obtained as products of the redox reactions in the system.

  • 46. Nagy, P.
    et al.
    Toth, I.
    Fabian, I.
    Maliarik, M.
    Glaser, Julius
    KTH, Tidigare Institutioner                               , Kemi.
    Kinetics and mechanism of formation of the platinum-thallium bond: The (CN)(5)Pt-Tl(CN)(3) (3-) complex2003Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 42, nr 21, s. 6907-6914Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Formation kinetics of the metal-metal bonded [(CN)(5)PtTl(CN)(3)](3-) complex from Pt(CN)(4)(2-) and Tl(CN)(4)(-) has been studied in the pH range-of 5-10, using standard mix-and-measure spectrophotometric technique at pH 5-8 and stopped-flow method at pH > 8. The overall order of the reaction, Pt(CN)(4)(2-) + Tl(CN)(4)(-) reversible arrow [(CN)(5)PtTl(CN)(3)](3-), is 2 in the slightly acidic region and 3 in the alkaline region, which means first order for the two reactants in both cases and also for CN- at high pH. The two-term rate law corresponds to two different pathways via the Tl(CN)(3) and Tl(CN)(4)(-) complexes in acidic and alkaline solution, respectively. The two complexes are in fast equilibrium, and their actual concentration ratio is controlled by the concentration of free cyanide ion. The following expression was derived for the pseudo-first-order rate constant of the overall reaction: k(obs) = (k(1)(a)[Tl(CN)(4)(-)] + (k(1)(a)/K-f))(1/(1 + K-p[H+]))[CN-](free) + k(1)(b) [Tl(CN)(4)(-)] + (k(1)(b)/K-f), where k(1)(a) and k(1)(b) are the forward rate constants for the alkaline and slightly acidic paths, K-f is the stability constant of [(CN)(5)PtTI(CN)(3)](3-), and K-p is the protonation constant of cyanide ion. k(1)(a) = 143 +/- 13 M-2 s(-1), k(1)(b) = 0.056 +/- 0.004 M-1 s(-1), K-f = 250 +/- 54 M-1, and log K-p = 9.15 +/- 0.05 (l = 1 M NaClO4, T = 298 K). Two possible mechanisms were postulated for the overall reaction in both pH regions, which include a metal-metal bond formation step and the coordination of the axial cyanide ion to the platinum center. The alternative mechanisms are different in the sequence of these steps.

  • 47. Nagy, P.
    et al.
    Toth, I.
    Fabian, I.
    Maliarik, M.
    Glaser, Julius
    KTH, Tidigare Institutioner, Kemi.
    Kinetics and mechanism of platinum-thallium bond formation: The binuclear (CN)(5)Pt-Tl(CN) (-) and the trinuclear (CN)(5)Pt-Tl-Pt(CN)(5) (3-) complex2004Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 43, nr 17, s. 5216-5221Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Formation kinetics of the metal-metal bonded binuclear [(CN)(5)Pt-TI(CN)](-) (1) and the trinuclear [(CN)(5)Pt-TI-Pt(CN)(5)](3-) (2) complexes is studied, using the standard mix-and-measure spectrophotometric method. The overall reactions are Pt(CN)(4)(2-) + TI(CN)(2)(+) z = 1 and Pt(CN)(4)(2-) + [(CN)(5)Pt-TI(CN)](-) = 2. The corresponding expressions for the pseudo-first-order rate constants are k(obs) = (k(1)[TI(CN)(2)(+)] + k(-1))[TI(CN)(2)(+)] (at TI(CN)(2)(+) excess) and k(obs) = (k(2b)[Pt(CN)(4)(2-)] + k(-2b))[HCN] (at Pt(CN)(4)(2-) excess), and the computed parameters are k(1) 1.04 +/-0.02 M-2 s(-1), k(-1) = k(1)/K-1 = 7 x 10(-5) M-1 s(-1) and k(2b) = 0.45 +/- 0.04 M-2 s(-1), K-2b = 26 +/- 6 M-1, k(-2b) = k(2b)/K-2b = 0.017 M-1 s(-1), respectively. Detailed kinetic models are proposed to rationalize the rate laws. Two important steps need to occur during the complex formation in both cases: (i) metal-metal bond formation and (ii) the coordination of the fifth cyanide to the platinum site in a nucleophilic addition. The main difference in the formation kinetics of the complexes is the nature of the cyanide donor in step ii. In the formation of [(CN)5Pt-TI(CN)]-, TI(CN)2+ is the source of the cyanide ligand, while HCN is the cyanide donating agent in the formation of the trinuclear species. The combination of the results with previous data predict the following reactivity order for the nucleophilic agents: CN- > TI(CN)(2)(+) > HCN.

  • 48. Nazeeruddin, M. K.
    et al.
    Wang, Q.
    Cevey, L.
    Aranyos, V.
    Liska, P.
    Figgemeier, E.
    Klein, C.
    Hirata, N.
    Koops, S.
    Haque, S. A.
    Durrant, J. R.
    Hagfeldt, Anders
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Lever, A. B. P.
    Gratzel, M.
    DFT-INDO/S modeling of new high molar extinction coefficient charge-transfer sensitizers for solar cell applications2006Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 45, nr 2, s. 787-797Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new ruthenium(II) complex, tetrabutylammonium [ruthenium (4-carboxylic acid-4'-carboxylate-2,2'-bipyridine)(4,4'-di(2-(3,6-dimethoxyphenyl)ethenyl)-2,2'-bipyridine)(NCS)(2)] (N945H), was synthesized and characterized by analytical, spectroscopic, and electrochemical techniques. The absorption spectrum of the N945H sensitizer is dominated by metal-to-ligand charge-transfer (MLCT) transitions in the visible region, with the lowest allowed MLCT bands appearing at 25 380 and 18 180 cm(-1). The molar extinction coefficients of these bands are 34 500 and 18 900 M-1 cm(-1), respectively, and are significantly higher when compared to than those of the standard sensitizer cis-dithiocyanatobis(4,4'-dicarboxylic acid-2,2'-bipyridine)ruthenium(II). An INDO/S and density functional theory study of the electronic and optical properties of N945H and of N945 adsorbed on TiO2 was performed. The calculations point out that the top three frontier-filled orbitals have essentially ruthenium 4d (t(2g) in the octahedral group) character with sizable contribution coming from the NCS ligand orbitals. Most critically the calculations reveal that, in the TiO2-bound N945 sensitizer, excitation directs charge into the carboxylbipyridine ligand bound to the TiO2 surface. The photovoltaic data of the N945 sensitizer using an electrolyte containing 0.60 M butylmethylimidazolium iodide, 0.03 M I-2, 0.10 M guanidinium thiocyanate, and 0.50 M tert-butylpyridine in a mixture of acetonitrile and valeronitrile (volume ratio = 85:15) exhibited a short-circuit photocurrent density of 16.50 +/- 0.2 mA cm(-2), an open-circuit voltage of 790 +/- 30 mV, and a fill factor of 0.72 +/- 0.03, corresponding to an overall conversion efficiency of 9.6% under standard AM (air mass) 1.5 sunlight, and demonstrated a stable performance under light and heat soaking at 80 degrees C.

  • 49. Nilsson, Kersti B.
    et al.
    Mallarik, Mikhail
    Persson, Ingmar
    Fischer, Andreas
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Ullstroem, Ann-Sofi
    Eriksson, Lars
    Sandstroem, Magnus
    Coordination chemistry of mercury(II) in liquid and aqueous ammonia solution and the crystal structure of tetraamminemercury(II) perchlorate2008Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 47, nr 6, s. 1953-1964Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The ammonia solvated mercury(II) ion has been structurally characterized in solution by means of EXAFS, Hg-199 NMR, and Raman spectroscopy and in solid solvates by combining results from X-ray single crystal and powder diffraction, thermogravimetry, differential scanning calorimetry, EXAFS, and Raman spectroscopy. Crystalline tetraamminemercury(II) perchlorate, [Hg(NH3)(4)](ClO4)(2), precipitates from both liquid ammonia and aqueous ammonia solution, containing tetraamminemercury(II) complexes. The orthorhombic space group (Pnma) imposes Q, symmetry on the tetraamminemercury(II) complexes, which is lost at a phase transition at about 220 K. The Hg-N bond distances are 2.175(14), 2.255(16), and 2 x 2.277(9) angstrom, with a wide N-Hg-N angle between the two shortest Hg-N bonds, 122.1(7)degrees, at ambient temperature, A similar distorted tetrahedral coordination geometry is maintained in liquid ammonia and aqueous ammonia solutions with the mean Hg-N bond distances 2.225(12) and 2.226(6) A, respectively. When heated to 400 K the solid tetraamminemercury(II) perchlorate decomposes to diamminemercury(II) perchlorate, [Hg(NH3)(2)](ClO4)(2), with the mean Hg-N bond distance 2.055(6) A in a linear N-Hg-N unit. The mercury atoms in the latter compound form a tetrahedral network, connected by perchlorate oxygen atoms, with the closest Hg center dot center dot center dot Hg distance being 3.420(3) angstrom. The preferential solvation and coordination changes of the mercury(II) ion in aqueous ammonia, by varying the total NH3:Hg(II) mole ratio from 0 to 130, were followed by Hg-199 NMR. Solid [Hg(NH3)(4)](ClO4)(2) precipitates while [Hg(H2O)(6)](2+) ions remain in solution at mole ratios below 3-4, while at high mole ratios, [Hg(NH3)4](2+) complexes dominate in solution. The principal bands in the vibrational spectrum of the [Hg(NH3)(4)](2+) complex have been assigned.

  • 50. Noack, Holger
    et al.
    Georgiev, Valentin
    Blomberg, Margareta R. A.
    Siegbahn, Per E. M.
    Johansson, Adam Johannes
    Aachen University.
    Theoretical Insights into Heme-Catalyzed Oxidation of Cyclohexane to Adipic Acid2011Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 50, nr 4, s. 1194-1202Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Adipic acid is a key compound in the chemical industry, where it is mainly used in the production of polymers. The conventional process of its generation requires vast amounts of energy and, moreover, produces environmentally deleterious substances. Thus, there is interest in alternative ways to gain adequate amounts of adipic acid. Experimental reports on a one-pot iron-catalyzed conversion of cyclohexane to adipic acid motivated a theoretical investigation based on density functional theory calculations. The process investigated is interesting because it requires less energy than contemporary methods and does not produce environmentally harmful side products. The aim of the present contribution is to gain insight into the mechanism of the iron-catalyzed cyclohexane conversion to provide a basis for the further development of this process. The rate-limiting step of the process is discussed, but considering the accuracy of the calculations, it is difficult to ensure whether the rate-limiting step is in the substrate oxidation or in the generation of the catalytically active species. It is shown that the slowest step in the substrate oxidation is the conversion of cyclohexanol to cyclohexane-1,2-diol. Hydrogen-atom transfer from one of the OH groups of cyclohexane-1,2-diol makes the intradiol cleavage occur spontaneously.

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