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  • 1. Abbasi, Alireza
    et al.
    Geranmayeh, Shokoofeh
    Skripkin, Mikhail Y.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Potassium ion-mediated non-covalent bonded coordination polymers2012In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 41, no 3, p. 850-859Article in journal (Refereed)
    Abstract [en]

    Crystal structures and vibrational spectra of three related network-forming coordination complexes have been studied. Two novel thermodynamically stable pseudo-polymorphic solvated rhodium chloro compounds, [cis-RhCl4(DMSO-kappa S)(2)K](n), 1, and [cis-RhCl4(DMSO-kappa S)(2)K center dot 3H(2)O](n), 2, and one metastable compound [trans-RhCl4(DMSO-kappa S)(2)K center dot 0.25H(2)O](n), 3, crystallize at ambient temperature in the orthorhombic space group P2(1)2(1)2(1) for 1, and the monoclinic space groups P2(1)/n and P2(1)/c for 2 and 3, respectively. All three structures contain [RhCl4(DMSO-kappa S)(2)]-complexes in which the rhodium(III) ions bind to two dimethyl sulfoxide (DMSO) sulfur atoms and four chloride ions in distorted octahedral coordination geometries. The complexes are connected in networks via potassium ions interacting with the Cl- and the DMSO oxygen atoms. As the sum of Shannon ionic radii of K+ and Cl- exceeds the K-Cl distances in compounds under study, these compounds can be described as Rh-Cl-K coordination polymers with non-covalent bonding, which is not common in these systems, forming 1- and 2-D networks for 1/2 and 3, respectively. The 2-D network with nano-layered sheets for compound 3 was also confirmed by TEM images. Further evaluation of the bonding in the cis- and trans-[RhCl4(DMSO-kappa S)(2)](-) entities was obtained by recording Raman and FT-IR absorption spectra and assigning the vibrational frequencies with the support of force-field calculations. The force field study of complexes reveals the strong domination of trans-effect (DMSO-kappa S > Cl) over the effect of non-covalent bonding in coordination polymeric structures. The comparison of calculated RhCl, RhS and SO stretching force constants showed evidence of K+-ligand interactions whereas direct experimental evidences of K+-Cl- interaction were not obtained because of strong overlap of the corresponding spectral region with that where lattice modes and Rh-ligand bendings appear.

  • 2. Abbasi, Alireza
    et al.
    Skripkin, Mikhail Yu.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Torapava, Natallia
    Ambidentate coordination of dimethyl sulfoxide in rhodium(III) complexes2011In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 40, no 5, p. 1111-1118Article in journal (Refereed)
    Abstract [en]

    The two dimethyl sulfoxide solvated rhodium(III) compounds, [Rh(dmso-kappa O)(5)(dmso-kappa S)](CF(3)SO(3))(3) (1 & 1* at 298 K and 100 K, respectively) and [Rh(dmso-kappa O)(3)(dmso-kappa S)(2)Cl](CF(3)SO(3))(2) (2), crystallize with orthorhombic unit cells in the space group Pna2(1) (No. 33), Z = 4. In the [Rh(dmso)(6)](3+) complex with slightly distorted octahedral coordination geometry, the Rh-O bond distance is significantly longer with O trans to S, 2.143(6) angstrom (1) and 2.100(6) angstrom (1*), than the mean Rh-O bond distance with O trans to O, 2.019 angstrom (1) and 2.043 angstrom (1*). In the [RhCl(dmso)(5)](3+) complex, the mean Rh-O bond distance with O trans to S, 2.083 angstrom, is slightly longer than that for O trans to Cl, 2.067(4) angstrom, which is consistent with the trans influence DMSO-kappa S > Cl > DMSO-kappa O of the opposite ligands. Raman and IR absorption spectra were recorded and analyzed and a complete assignment of the vibrational bands was achieved with support by force field calculations. An increase in the Rh-O stretching vibrational frequency corresponded to a decreasing trans-influence from the opposite ligand. The Rh-O force constants obtained were correlated with the Rh-O bond lengths, also including previously obtained values for other M(dmso)(6)(3+) complexes with trivalent metal ions. An almost linear correlation was obtained for the MO stretching force constants vs. the reciprocal square of the MO bond lengths. The results show that the metal ion-oxygen bonding of dimethyl sulfoxide ligands is electrostatically dominated in those complexes and that the stretching force constants provide a useful measure of the relative trans-influence of the opposite ligands in hexa-coordinated Rh(III)-complexes.

  • 3.
    Ahlsten, Nanna
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bartoszewicz, Agnieszka
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martín-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Allylic alcohols as synthetic enolate equivalents: Isomerisation and tandem reactions catalysed by transition metal complexes2012In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 41, no 6, p. 1660-1670Article in journal (Refereed)
    Abstract [en]

    Allylic alcohols can be isomerised into carbonyl compounds by transition metal complexes. In the last few years, catalyst design and development have resulted in highly efficient isomerisations under mild reaction conditions, including enantioselective versions. In addition, the isomerisation of allylic alcohols has been combined with C-C bond forming reactions when electrophiles such as aldehydes or imines were present in the reaction mixture. Also, C-F bonds can be formed when electrophilic fluorinating reagents are used. Thus, allylic alcohols can be treated as latent enol(ate)s. In this article, we highlight the latest developments concerning the isomerisation of allylic alcohols into carbonyl compounds, focusing in particular on tandem isomerisation/C-C or C-heteroatom bond formation processes. Significant attention is given to the mechanistic aspects of the reactions.

  • 4. Alammar, Tarek
    et al.
    Hlova, Ihor Z.
    Gupta, Shalabh
    Balema, Viktor
    Pecharsky, Vitalij K.
    Mudring, Anja-Verena
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Iowa State University, USA.
    Luminescence properties of mechanochemically synthesized lanthanide containing MIL-78 MOFs2018In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 47, no 22, p. 7594-7601Article in journal (Refereed)
    Abstract [en]

    Three metal-organic framework (MOF) compounds, Ln(0.6) Gd-0.(6) {C6H (COO)(3)); Ln = Eu, Tb, and Dy with a MIL-78 structure, have been synthesized by a solvent-free mechanochemical method from stoichiometric mixtures of benzene 1,3,5-tricarboxylic acid, C6H3 (COOH)(3), also known as trimesic acid, and the respective lanthanide carbonates, Ln(2)(CO3)(3)center dot xH(2)O, Ln = Eu, Gd, Tb and Dy. MIL-78 (Ln(0.5)Gd(0.)(6)) shows the characteristic red, green, and yellow luminescence of Eu3+, Tb3+, and Dy3+, respectively. Efficient intramolecular energy transfer from the ligand triplet state to the excited states of Ln(3+) ions can be observed. The lifetimes and quantum yields of these compounds are studied and discussed in detail. Among the three compounds, the Tb3+ containing compound shows the longest lifetime and highest quantum yield due to a smaller contribution from non-radiative decay pathways and better matching of the lowest triplet energy level of the benzenetricarboxylate ligand and the resonance level of Tb3+.

  • 5.
    Ali, Sk Imran
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Johnsson, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Antimony oxofluorides - a synthesis concept that yields phase pure samples and single crystals2016In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 45, no 30, p. 12167-12173Article in journal (Refereed)
    Abstract [en]

    The single crystals of the new isostructural compounds Sb3O4F and Y0.5Sb2.5O4F and the two previously known compounds M-SbOF and alpha-Sb3O2F5 were successfully grown by a hydrothermal technique at 230 degrees C. The new compound Sb3O4F crystallizes in the monoclinic space group P2(1)/c: a = 5.6107(5) angstrom, b = 4.6847(5) angstrom, c = 20.2256(18) angstrom, p = 94.145(8)degrees, z = 4. The replacing part of Sb with Y means a slight increase in the unit cell dimensions. The compounds M-SbOF and alpha-Sb3O2F5 have not been grown as single crystals before and it can be concluded that hydrothermal synthesis has proved to be a suitable technique for growing single crystals of antimony oxofluorides because of the relatively low solubility of such compounds compared to other antimony oxohalides that most often have been synthesised at high temperatures by solid state reactions or gas-solid reactions.

  • 6. Berggren, Gustav
    et al.
    Huang, Ping
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Styring, Stenbjorn
    Anderlund, Magnus F.
    Thapper, Anders
    Synthesis and characterisation of low valent Mn-complexes as models for Mn-catalases2010In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 39, no 45, p. 11035-11044Article in journal (Refereed)
    Abstract [en]

    In this work we report the synthesis of two novel manganese complexes, [L1(3)Mn(6)(II)](ClO4)(6) (1 center dot(ClO4)(6)) and [L2Mn(2)(II)(mu-OAc)(mu-Cl)](ClO4)(2) (2 center dot(ClO4)(2)), where L1(2-) is the 2,2'-(1,3-phenylenebis(methylene))bis-((2-(bis(pyridin-2-ylmethyl)amino)ethyl)azanediyl)diacetic acid anion and L2 is N1,N1'-(1,3-phenylenebis(methylene))bis(N2,N2'-bis(pyridin-2-ylmethyl)ethane-1,2-diamine). The ligands Na(2)L1 and L2 are built on the same backbone, L2 only contains nitrogen donors, while two carboxylate arms have been introduced in Na(2)L1. The two complexes have been characterized by single-crystal X-ray diffraction, magnetic susceptibility, EPR spectroscopy, and electrochemistry. X-Ray crystallography revealed that 1 is a manganese(II) hexamer and 2 is a manganese(II) dimer featuring an unprecedented mono-mu-acetato, mono-mu-chlorido bridging motif. The ability of the complexes to catalyse H2O2 disproportionation, thereby acting as models for manganese catalases, has been investigated and compared to the activity of two other related manganese complexes. The introduction of carboxylate donors in the ligands, leading to increased denticity, resulted in a drop in H2O2 disproportionation activity.

  • 7. Berggren, Gustav
    et al.
    Thapper, Anders
    Anderlund, Magnus
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Two tetranuclear Mn-complexes as biomimetic models of the oxygen evolving complex in Photosystem II - A synthesis, characterisation and reactivity study2009In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 45, p. 10044-10054Article in journal (Refereed)
    Abstract [en]

    In this work we report the preparation of two metallamacrocyclic tetranuclear manganese(II) complexes, [L1(4)Mn(4)](ClO4)(4) and [L2(4)Mn(4)](ClO4)(4) where L1 and L2 are the anions of the heptadentate ligands 2-((2-(bis(pyridin-2-ylmethyl) amino) ethyl)(methyl) amino) acetic acid and 2-(benzyl(2-(bis(pyridin-2-ylmethyl) amino) ethyl) amino) acetic acid), respectively. The complexes have been fully characterized by ESI-MS, elemental analysis, single-crystal X-ray diffraction, magnetic susceptibility, and EPR spectroscopy. Electrochemical reactions as well as reactions with different chemical redox reagents have been performed and a reversible two electron oxidation per manganese ion has been identified. The reaction of [L1(4)Mn(4)](ClO4)(4) with oxone or cerium(IV) results in the evolution of oxygen which makes this system interesting for future studies in the search for a functional mimic of the oxygen evolving complex in Photosystem II.

  • 8. Cadu, Alban
    et al.
    Andersson, Pher G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Council for Scientific & Industrial Research (CSIR) - South Africa .
    Iridium catalysis: application of asymmetric reductive hydrogenation2013In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 42, no 40, p. 14345-14356Article in journal (Refereed)
    Abstract [en]

    Iridium, despite being one of the least abundant transition metals, has found several uses. N,P-ligated iridium catalysts are used to perform many highly selective reactions. These methodologies have been developed extensively over the past 15 years. More recently, the application of iridium N,P catalysts in asymmetric hydrogenation has been a focus of research to find novel applications and to expand on their current synthetic utility. The aim of this perspective is to highlight the advances made by the Andersson group.

  • 9.
    Chen, Hong
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). China University of Geosciences - Wuhan, People's Republic of China.
    Zhang, Yunfeng
    Yu, Zhengbao
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Peking University, People's Republic of China.
    Layered V-B-O Polyoxometalate Nets Linked by Diethylenetriamine Complexes with Dangling Amine Groups2014In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 43, no 41, p. 15283-15286Article in journal (Refereed)
    Abstract [en]

    Two layered V-B-O contained polyoxometalate (POM) net structures, denoted as SUT-12 and SUT-13, are reported here. SUT-12 was synthesized by the boric acid flux method, and it represents the first 2D structure constructed from the V6B20 vanadoborate cluster. SUT-13 was synthesized through the hydrothermal method and constructed from V12B6P12 vanadium borophosphate clusters. In both structures, the vanadoborate or vanadium borophosphate clusters were linked through in-situ formed Zn(DETA)2 or Cu(DETA)2 complexes. Surprisingly, for all DETA molecules in the two metal complexes, there is one dangling amine group when it coordinated to the metal. The phenomena of the dangling amine group feature is abnormal and the Cu(DETA)2 complexes in SUT-13 was taken as an example and studied by density function theory (DFT) calculation in order to understand this unusual feature.

  • 10.
    Damian, Emiliana
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Jalilehvand, Farideh
    Leung, Bonnie
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    Sandström, Magnus
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Theoretical and experimental sulfur K-edge X-ray absorption spectroscopic (XANES) study of cysteine, cystine, methionine and methionine sulfoxide2009In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 18, p. 3542-3558Article in journal (Refereed)
    Abstract [en]

    The experimental sulfur K-edge x-ray absorption near edge structure (XANES) spectra of the amino acids cysteine, homocysteine, penicillamine, methionine, the oxidation products methionine sulfoxide and the disulfide cystine, have been analyzed by transition potential DFT calculations. The absolute energies and intensities of the main pre-edge sulfur 1s electron transitions have been computed to determine the character of the receiving low energy unoccupied molecular orbitals (MO), and to investigate the influence of external interactions, especially by introducing water molecules hydrogen bonded to the ionic species present in different pH ranges. When the thiol group deprotonates for the three amino acids cysteine, homocysteine and penicillamine the energy of the main transition, to an MO with antibonding σ*(S-H) character, reduces by ~1.1 eV and the receiving MO obtains σ*(S-C) character. The energy shifts due to hydrogen bonding were in most cases found to be relatively small, although the transition intensities could vary significantly due to the changes induced in the molecular charge distribution, thereby affecting the shapes of the spectral features. For the cysteine and penicillamine zwitterions deconvolution of the experimental spectra allowed the microscopic acid dissociation constants to be extracted separately for the thiol and the protonated amine groups, pKaT = 8.5 ± 0.1 and 8.2 ± 0.1, and pKaN = 8.9 ± 0.1 and 8.8 ± 0.1, respectively, in both cases with the thiol group the more acidic. Coordination of cysteine to nickel(II) or mercury(II) introduced a new low energy transition involving metal ion orbitals in the receiving LUMO. The small experimentally observed energy differences between the similar main absorption features of the cysteine and methionine zwitterions, 0.2-0.3 eV in comparable surrounding, as well as a minor difference in their intensity ratio, are reflected in the calculated transitions. The S K-edge XANES spectrum of the disulfide cystine displays a characteristic double peak with the lower energy transition (2469.9 eV) into the antibonding σ*(S-S) MO. The second peak, at 2471.5 eV in aqueous solution, contains several transitions into MO:s with σ*(S-C) character involving also charge transfer to the water molecules hydrating the protonated amine groups (NH3+) of cystine. The experimental energy difference between the two peaks increases by 0.2 eV for solid cystine, while no such increase occurs for the –S-S- bond between the cysteine residues in the oxidized disulfide of glutathione, where the amine groups are engaged in peptide bonds. This study shows that externally induced changes in the intramolecular bonding, e.g. by coordination, conformation geometry or hydrogen bonding, can significantly influence the S K-edge spectra, and emphasizes the importance of a similar chemical surrounding of the model compounds for standard spectra of sulfur functional groups, used to deconvolute composite experimental spectra.

  • 11. Das, Biswanath
    et al.
    Lee, Bao-Lin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Karlsson, Erik A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Torbjörn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Shatskiy, Andrey
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Demeshko, Serhiy
    Liao, Rong-Zhen
    Laine, Tanja M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Haukka, Matti
    Zeglio, Erica
    Abdel-Magied, Ahmed F.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Siegbahn, Per E. M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Meyer, Franc
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nordlander, Ebbe
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Water oxidation catalyzed by molecular di- and nonanuclear Fe complexes: importance of a proper ligand framework2016In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 45, no 34, p. 13289-13293Article in journal (Refereed)
    Abstract [en]

    The synthesis of two molecular iron complexes, a dinuclear iron(III,III) complex and a nonanuclear iron complex, based on the di-nucleating ligand 2,2'-(2-hydroxy-5-methyl-1,3-phenylene)bis(1H-benzo[d]imidazole-4-carboxylic acid) is described. The two iron complexes were found to drive the oxidation of water by the one-electron oxidant [Ru(bpy)(3)](3+).

  • 12.
    Guo, Peng
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Liu, Leifeng
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Yun, Yifeng
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Su, Jie
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Wan, Wei
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Gies, Hermann
    Zhang, Haiyan
    Xiao, Feng-Shou
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Ab initio structure determination of interlayer expanded zeolites by single crystal rotation electron diffraction2014In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 43, no 27, p. 10593-10601Article in journal (Refereed)
    Abstract [en]

    Layered solids often form thin plate-like crystals that are too small to be studied by single-crystal X-ray diffraction. Although powder X-ray diffraction (PXRD) is the conventional method for studying such solids, it has limitations because of peak broadening and peak overlapping. We have recently developed a software-based rotation electron diffraction (RED) method for automated collection and processing of 3D electron diffraction data. Here we demonstrate the ab initio structure determination of two interlayer expanded zeolites, the microporous silicates COE-3 and COE-4 (COE-n stands for International Network of Centers of Excellence-n), from submicron-sized crystals by the RED method. COE-3 and COE-4 are built of ferrierite-type layers pillared by (-O-Si(CH3)(2)-O-) and (-O-Si(OH)(2)-O-) linker groups, respectively. The structures contain 2D intersecting 10-ring channels running parallel to the ferrierite layers. Because both COE-3 and COE-4 are electron-beam sensitive, a combination of RED datasets from 2 to 3 different crystals was needed for the structure solution and subsequent structure refinement. The structures were further refined by Rietveld refinement against the PXRD data. The structure models obtained from RED and PXRD were compared.

  • 13.
    Hu, Shichao
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Johnsson, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Synthesis and crystal structure of Fe6Ca2(SeO3)(9)Cl-4 - a porous oxohalide2013In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 42, no 22, p. 7859-7862Article in journal (Refereed)
    Abstract [en]

    A porous oxohalide, Fe6Ca2(SeO3)(9)Cl-4, has been synthesized by solid state reactions using concentrated HCl as the Cl-source. It crystallizes in the hexagonal space group P6(3)/m with unit cell parameters a = 12.118(2) angstrom, c = 12.703(4) angstrom, Z = 2. The crystal structure is an open framework having one-dimensional channels extending along [001] that the chlorine atoms and lone pairs on Se4+ are facing. The channels in this framework structure are unusually large compared to other oxohalide compounds and also accessible to guest molecules. Water vapor sorption measurements show an uptake of 9 wt% at 293 K.

  • 14.
    Hu, Shichao
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Johnsson, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Synthesis and crystal structure of two synthetic oxofluoride framework compounds - Co2TeO3F2 and Co2SeO3F22012In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 41, no 41, p. 12786-12789Article in journal (Refereed)
    Abstract [en]

    Two new isostructural Co2+ containing tellurium and selenium oxofluoride compounds Co2TeO3F2 and Co2SeO3F2 are synthesized and their structures determined by single crystal X-ray diffraction. They crystallize in the orthorhombic space group Pnma with the unit cell parameters a = 7.3810(5) angstrom, b = 10.1936(7) angstrom, c = 5.3013(3) angstrom and a = 7.2655(8) angstrom, b = 10.0013(13) angstrom, c = 5.3564(6) angstrom, respectively. The Co(II) ion has octahedral coordination [CoO3F3] and builds up a 3D framework by corner- and edge sharing. The Se(IV) and the Te(IV) ions have the coordinations [SeO3E] and [TeO3E] respectively where E is the lone-pair electrons. The Se(IV) and Te(IV) ions are isolated from each other and bond only to the [CoO3F3] polyhedra. The electronegative element fluorine takes the role of a network builder like oxygen and helps to form the 3D framework structure. This is a difference compared to many oxohalide compounds containing Cl and Br where the halide ions are terminating ions preventing a 3D network from being formed. Long range antiferromagnetic interactions dominate at temperatures < 20 K. The magnetic susceptibility follows the Curie-Weiss law above 25 K with the Curie constant C = 5.62 emu K mol(-1), the Weiss temperature theta = -56 K and the effective magnetic moment mu(eff) = 4.74 mu(B) per cobalt atom.

  • 15. Huang, Jing
    et al.
    Gatty, Melina Gilbert
    Xu, Bo
    Pati, Palas Baran
    Etman, Ahmed S.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Tian, Lei
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hammarström, Leif
    Tian, Haining
    Covalently linking CuInS2 quantum dots with a Re catalyst by click reaction for photocatalytic CO2 reduction2018In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 47, no 31, p. 10775-10783Article in journal (Refereed)
    Abstract [en]

    Covalently linking photosensitizers and catalysts in an inorganic-organic hybrid photocatalytic system is beneficial for efficient electron transfer between these components. However, general and straightforward methods to covalently attach molecular catalysts on the surface of inorganic semiconductors are rare. In this work, a classic rhenium bipyridine complex (Re catalyst) has been successfully covalently linked to the low toxicity CuInS2 quantum dots (QDs) by click reaction for photocatalytic CO2 reduction. Covalent bonding between the CuInS2 QDs and the Re catalyst in the QD-Re hybrid system is confirmed by UV-visible absorption spectroscopy, Fourier-transform infrared spectroscopy and energy-dispersive X-ray measurements. Time-correlated single photon counting and ultrafast time-resolved infrared spectroscopy provide evidence for rapid photo-induced electron transfer from the QDs to the Re catalyst. Upon photo-excitation of the QDs, the singly reduced Re catalyst is formed within 300 fs. Notably, the amount of reduced Re in the linked hybrid system is more than that in a sample where the QDs and the Re catalyst are simply mixed, suggesting that the covalent linkage between the CuInS2 QDs and the Re catalyst indeed facilitates electron transfer from the QDs to the Re catalyst. Such an ultrafast electron transfer in the covalently linked CuInS2 QD-Re hybrid system leads to enhanced photocatalytic activity for CO2 reduction, as compared to the conventional mixture of the QDs and the Re catalyst.

  • 16.
    Huang, Shiliang
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Inge, A. Ken
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Yang, Sihai
    Christensen, Kirsten E.
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    SU-75: a disordered Ge-10 germanate with pcu topology2012In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 41, no 40, p. 12358-12364Article in journal (Refereed)
    Abstract [en]

    A disordered open-framework germanate, denoted as SU-75, was synthesized under hydrothermal conditions using diethylenetriamine (dien) or alternatively 1,4-diaminobutane (dab) as the structure directing agent (SDA). SU-75 crystallizes in a tetragonal space group I-42d(No. 122) with a= 18.145(3) Å and c= 41.701(9) Å. The three-dimensional (3D) framework is built from Ge10(O,OH)28(Ge10) clusters that are connected following the pcu ( primitive cubic) net topology. SU-75 has 10-, 11- and 12-ring channels along the a- and b-axes and channels with alternating 8-, 10-, 12-, 10-ring openings along the c-axis. The framework exhibits a serious disorder, resulted from two possible connectivities between the units of four Ge 10clusters (4Ge10 unit). The chemical formula of SU-75 is |(H2SDA)2(H2O)n|[Ge10O21(OH)2] (SDA = dien or dab,n= 5–6), determined by combining single crystalsynchrotron X-ray diffraction, thermogravimetric analysis (TGA) and CHN elemental analysis. A superoctahedron is introduced to simplify the description of the connectivity of the Ge10 clusters and to illustrate the disorder. This is also used to compare the structure of SU-75 with those of related Ge10 germanates.

  • 17.
    Johansson, Adam Johannes
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Noack, Holger
    Stockholm University, Faculty of Science, Department of Physics.
    Xue, Gengianq
    Que Jr, Larry
    Observed enhancement of the reactivity of a biomimetic diiron complex by the addition of water - mechanistic insights from theoretical modeling2009In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 34, p. 6741-6750Article in journal (Refereed)
    Abstract [en]

    The biomimetic diiron complex [FeIIIFeIV(m-O)2(5-Me3-TPA)2](ClO4)3 (TPA = tris(2- pyridylmethyl)amine) has been found to be capable of oxidizing 9,10-dihydroanthracene in a solution of acetonitrile. Addition of water up to 1 M makes the reaction 200 times faster, suggesting that the water molecule in some way activates the catalyst for more efficient substrate oxidation. It is proposed that the enhanced reactivity results from the coordination of a water molecule to the iron(III) half of the complex, converting the bis-m-oxo structure of the diiron complex to a ring-opened form where one of the bridging oxo groups is transformed into a terminal oxo group on iron(IV). The suggested mechanism is supported by DFT (B3LYP) calculations and transition state theory. Two different computational models of the diiron complex are used to model the hydroxylation of cyclohexane to cyclohexanol. Model 1 has a bis-m-oxo diiron core (diamond core) while model 2 represents the “open core” analogue with one bridging m-oxo group, a terminal oxo ligand on iron(IV), and a water molecule coordinated to iron(III). The computational results clearly suggest that the terminal oxo group is more reactive than the bridging oxo group. The free energy of activation is 7.0 kcal mol-1 lower for the rate limiting step when the oxidant has a terminal oxo group than when both oxo groups are bridging the irons.

  • 18.
    Kärkäs, Markus D.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Water oxidation using earth-abundant transition metal catalysts: opportunities and challenges2016In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 45, no 37, p. 14421-14461Article in journal (Refereed)
    Abstract [en]

    Catalysts for the oxidation of H2O are an integral component of solar energy to fuel conversion technologies. Although catalysts based on scarce and precious metals have been recognized as efficient catalysts for H2O oxidation, catalysts composed of inexpensive and earth-abundant element(s) are essential for realizing economically viable energy conversion technologies. This Perspective summarizes recent advances in the field of designing homogeneous water oxidation catalysts (WOCs) based on Mn, Fe, Co and Cu. It reviews the state of the art catalysts, provides insight into their catalytic mechanisms and discusses future challenges in designing bioinspired catalysts based on earth-abundant metals for the oxidation of H2O.

  • 19. Li, Wenjie
    et al.
    Li, Duan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Gao, Xin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Gurlo, Aleksander
    Zander, Stefan
    Jones, Philip
    Navrotsky, Alexandra
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Riedel, Ralf
    Ionescu, Emanuel
    A study on the thermal conversion of scheelite-type ABO(4) into perovskite-type AB(O,N)(3)2015In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 44, no 17, p. 8238-8246Article in journal (Refereed)
    Abstract [en]

    Phase-pure scheelite AMoO(4) and AWO(4) (A = Ba, Sr, Ca) were thermally treated under an ammonia atmosphere at 400 to 900 degrees C. SrMoO4 and SrWO4 were shown to convert into cubic perovskite SrMoO2N and SrWO1.5N1.5, at 700 degrees C and 900 degrees C respectively, and to form metastable intermediate phases (scheelite SrMoO4-xNx and SrWO4-xNx), as revealed by X-ray diffraction (XRD), elemental analysis and FTIR spectroscopy. High-temperature oxide melt solution calorimetry reveals that the enthalpy of formation for SrM(O,N)(3) (M = Mo, W) perovskites is less negative than that of the corresponding scheelite oxides, though the conversion of the scheelite oxides into perovskite oxynitrides is thermodynamically favorable at moderate temperatures. The reaction of BaMO4 with ammonia leads to the formation of rhombohedral Ba3M2(O,N)(8) and the corresponding binary metal nitrides Mo3N2 and W4.6N4; similar behavior was observed for CaMO4, which converted upon ammonolysis into individual oxides and nitrides. Thus, BaMO4 and CaMO4 were shown to not provide access to perovskite oxynitrides. The influence of the starting scheelite oxide precursor, the structure distortion and the degree of covalency of the B-site-N bond are discussed within the context of the formability of perovskite oxynitrides.

  • 20.
    Li, Xichen
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Chen, Guangju
    Schinzel, Sandra
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Siegbahn, Per E. M.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    A comparison between artificial and natural water oxidation2011In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 40, no 42, p. 11296-11307Article in journal (Refereed)
    Abstract [en]

    Two artificial water oxidation catalysts, the blue dimer and the Llobet catalyst, have been studied using hybrid DFT methods. The results are compared to those for water oxidation in the natural photosystem II enzyme. Studies on the latter system have now reached a high level of understanding, at present much higher than the one for the artificial systems. A recent high resolution X-ray structural investigation of PSII has confirmed the main features of the structure of the oxygen evolving complex (OEC) suggested by previous DFT cluster studies. The O-O bond formation mechanism suggested is of direct coupling (DC) type between an oxygen radical and a bridging oxo ligand. A similar DC mechanism is found for the Llobet catalyst, while an acid-base (AB) mechanism is preferred for the blue dimer. All of them require at least one oxygen radical. Full energy diagrams, including both redox and chemical steps, have been constructed illustrating similarities and differences to the natural system. Unlike previous DFT studies, the results of the present study suggest that the blue dimer is rate-limited by the initial redox steps, and the Llobet catalyst by O(2) release. The results could be useful for further improvement of the artificial systems.

  • 21. Liang, Jie
    et al.
    Su, Jie
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Chen, Yanping
    Li, Zhaofei
    Li, Kuo
    Zhang, Hao
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Liao, Fuhui
    Wang, Yingxia
    Lin, Jianhua
    Syntheses, structure solutions, and catalytic performance of two novel layered silicates2015In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 44, no 35, p. 15567-15575Article in journal (Refereed)
    Abstract [en]

    Two novel layered silicates, PKU-13 and PKU-13a, were hydrothermally synthesized by using trimethyl-propylammonium hydroxide as the structure directing agent (SDA). Their structures were solved by using powder X-ray diffraction data in combination with electron diffraction technique and NMR spectroscopy. These two silicates are built from the same r52 layer in different stacking modes: the adjacent r52 layers in PKU-13a have a 0.5b + 0.68c shift compared with those in PKU-13. The difference is due to the SDA cations located between the layers. The SDA cations exist as a monolayer in the structure of PKU-13, and link the adjacent layers by Coulomb actions in combination with strong hydrogen bonds. In PKU-13a, the SDA cations present in the bi-layer expend the distance between layers and destroy the inter-layer hydrogen bonds. PKU-13a can transform to PKU-13 after treatment with acetic acid solution. The co-existence of intra-layer hydrogen bonds in PKU-13 interfere in its condensation to an ordered crystalline microporous framework. Both PKU-13 and PKU-13a exhibit good catalytic activities as base catalysts in the Knoevenagel condensation reaction.

  • 22. Liao, Rong-Zhen
    et al.
    Wang, Mei
    Sun, Licheng
    Siegbahn, Per E. M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    The mechanism of hydrogen evolution in Cu(bztpen)-catalysed water reduction: a DFT study2015In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 44, no 21, p. 9736-9739Article in journal (Refereed)
    Abstract [en]

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

  • 23.
    Nyhlén, Jonas
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Privalov, Timofei
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    On the possibility of catalytic reduction of carbonyl moieties with tris(pentafluorophenyl)borane and H2: a computational study2009In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, no 29, p. 5780-5786Article in journal (Refereed)
    Abstract [en]

    The study thoroughly examines the Gibbs free energy surfaces of a new mechanism for redn. of ketones/aldehydes by tris(pentafluorophenyl)borane (1) and H2. Key elements of the proposed mechanism are the proton and the hydride transfer steps similar to Stephan's catalytic redn. of imines by 1. The proton is transferred to the ketone/aldehyde in the process of H2 cleavage by the carbonyl-borane couple and the hydride is transferred in a nucleophilic attack on the carbonyl carbon by the hydridoborate in the ionic pair, [HOCRR']+[HB(C6F5)3]-. The in solvent Gibbs free energy barriers of H2 splitting by adducts of B(C6F5)3 with acetone, acetophenone and benzaldehyde are predicted to be in the range of 24.5 ± 2.5 kcal mol-1, which corresponds to potential energy barriers in the range of 17.0 ± 2.0 kcal mol-1. Significantly lower barrier of H2 activation is predicted in cases of bulky ketones such as 2,2,4,4-tetramethylpentan-3-one. With respect to the hydridoborate intermediate, the nucleophilic attack on the activated carbon is predicted to have a relatively low barrier for the sterically unhindered substrates, while this barrier is considerably higher for the sterically encumbered substrates. Since the formation of the hydridoborate intermediates is found to be endothermic, the transition state of the nucleophilic attack is the highest point of the computed energy profile for all tested substrates. Overall, according to in solvent d. function calcns. the proposed redn. of "compact" ketones/aldehydes by 1 and H2 is allowed both thermodynamically and kinetically at elevated temp., but it is expected to be slower and more substrate specific than the corresponding redn. of imines. [on SciFinder(R)]

  • 24.
    Privalov, Timofei
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hydrogenation of imines by phosphonium borate zwitterions: a theoretical study2009In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. -, no 8, p. 1321-1327Article in journal (Refereed)
  • 25.
    Rabbani, Faiz
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Svengren, Henrik
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zimmermann, Iwan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hu, Shichao
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Laine, Tanja
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hao, Wenming
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Torbjörn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnsson, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Cobalt selenium oxohalides: catalysts for water oxidation2014In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 43, no 10, p. 3984-33989Article in journal (Refereed)
    Abstract [en]

    Two new oxohalides Co4Se3O9Cl2 and Co3Se4O10Cl2 have been synthesized by solid state reactions. They crystallize in the orthorhombic space group Pnma and the monoclinic space group C2/m respectively. The crystal structure of the two compounds are made up of similar building blocks; Co4Se3O9Cl2 is made up of [CoO4Cl2], [CoO5Cl] and [SeO3] polyhedra and Co3Se4O10Cl2 is made up of [CoO4Cl2] and [SeO3] polyhedra. As several Co-containing compounds have proved to be good catalysts for water oxidation, the activities of the two new compounds were compared with the previously found oxohalide Co5Se4O12Cl2 in reference to CoO and CoCl2. The one electron oxidant Ru(bpy)33+ was used as oxidizing species in a phosphate buffer and it was found that the activities of the oxohalide species were in between CoO and CoCl2. The roles of Cl and PO43− ions are discussed.

  • 26.
    Rabten, Wangchuk
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Torbjörn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Chen, Hong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). China University of Geosciences, China.
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Peking University, China.
    Andersson, Pher G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    A ruthenium water oxidation catalyst based on a carboxamide ligand2016In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 45, no 8, p. 3272-3276Article in journal (Refereed)
    Abstract [en]

    Herein is presented a single-site Ru complex bearing a carboxamide-based ligand that efficiently manages to carry out the fourelectron oxidation of H2O. The incorporation of the negatively charged ligand framework significantly lowered the redox potentials of the Ru complex, allowing H2O oxidation to be driven by the mild oxidant [Ru(bpy)(3)](3+). This work highlights that the inclusion of amide moieties into metal complexes thus offers access to highly active H2O oxidation catalysts.

  • 27. Rahman, Seikh M. H.
    et al.
    Norberg, Stefan T.
    Knee, Christopher S.
    Biendicho, Jordi J.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). STFC Rutherford Appleton Laboratory, England.
    Hull, Stephen
    Eriksson, Sten G.
    Proton conductivity of hexagonal and cubic BaTi1-XScxO3-delta (0.1 <= x <= 0.8)2014In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 43, no 40, p. 15055-15064Article in journal (Refereed)
    Abstract [en]

    BaTi1-xScxO3-delta (X = 0.1-0.8) was prepared via solid state reaction. High resolution X-ray powder diffraction was used to characterise the synthesised materials. It was found that low substitution (x = 0.1 and 0.2) of Ti4+ for Sc3+ gives a hexagonal perovskite structure, whereas high substitution (x = 0.5-0.7) results in a cubic perovskite structure. Thermogravimetric analysis revealed significant levels of protons in both as-prepared and hydrated samples. Electrical conductivity was measured by AC impedance methods under oxygen, argon and under dry and humid, both H(2)0 and D2O, conditions for BaTi1-xScXO3-delta,(x = 0.2, 0.6 and 0.7). In the temperature range of 150-600 C-circle, under humid conditions, the conductivity is significantly higher than that under the dry conditions. The increase in conductivity is especially prominent for the cubic phases, indicating that protons are the dominant charge carriers. The proton conductivity of hexagonal BaTi0.8,Sc0.2O3-delta is approx. two orders of magnitude lower than that of the more heavily substituted cubic phases. Conductivity is also found to be higher in dry O-2 than in Ar in the whole temperature range of 150-1000 C-circle, characteristic of a significant contribution from p-type charge carriers under oxidising atmospheres. Greater Sc3+ substitution leads to a higher proton concentration and the highest proton conductivity (sigma similar to 2 x 10(-3) S cm(-1) at 600 degrees C) is found for the BaTi(0.3)Sc(07)cO(3-delta) composition.

  • 28. Risberg, Emiliana Damian
    et al.
    Jalilehvand, Farideh
    Leung, Bonnie O.
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    Sandström, Magnus
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Theoretical and Experimental Sulfur K-edge X-ray Absorption Spectroscopic Study of Cysteine, Cystine, Homocysteine, Penicillamine, Methionine and Methionine Sulfoxide2009In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, p. 3542-3558Article in journal (Refereed)
    Abstract [en]

      The experimental sulfur K-edge X-ray absorption near-edge structure (XANES) spectra of the amino acids cysteine, homocysteine, penicillamine, methionine, including the oxidation products methionine sulfoxide and the disulfide cystine, have been analyzed by transition potential DFT calculations. The absolute energies and intensities of the main pre-edge sulfur 1s electron transitions have been computed to determine the character of the receiving unoccupied molecular orbitals (MO), and to investigate the influence of external interactions, especially by introducing water molecules hydrogen-bonded to the ionic species present in different pH ranges. When the thiol group deprotonates for cysteine, homocysteine and penicillamine and also for the cysteine residue in glutathione the energy of the main transition, to an MO with antibonding σ*(S–H) character, reduces by 1.1 eV and the receiving MO obtains σ*(S–C) character. The changes in transition energy due to hydrogen-bonding were in most cases found to be relatively small, although the transition intensities could vary significantly due to the changes induced in the molecular charge distribution, thereby affecting the shapes of the spectral features. For the cysteine and penicillamine zwitterions deconvolution of the experimental spectra allowed the microscopic acid dissociation constants to be extracted separately for the thiol and the protonated amine groups, pKaS = 8.5 ± 0.1 and 8.2 ± 0.1, and pKaN = 8.9 ± 0.1 and 8.8 ± 0.1, respectively, with the thiol group in both cases being the more acidic. Coordination of cysteine to nickel(II) or mercury(II) introduced a new low energy transition involving metal ion orbitals in the receiving LUMO. The small experimentally observed energy differences between the similar main absorption features of the cysteine and methionine zwitterions, 0.2–0.3 eV in comparable surrounding, as well as a minor difference in their intensities, are reflected in the calculated transitions. The S K-edge XANES spectrum of the disulfide cystine displays a characteristic double peak with the lower energy transition (2469.9 eV) into the antibonding σ*(S–S) MO. The second peak, at 2471.5 eV in aqueous solution, contains several transitions into MOs with σ*(S–C) character involving also charge transfer to the water molecules hydrating the protonated amine groups (NH3+) of cystine. For solid cystine without hydrogen bonding the experimental energy difference between the two peaks is 0.2 eV larger, while no such increase occurs for the oxidized disulfide of glutathione, with a similar –S–S– bond between its cysteine residues as in cystine, because the amine groups are engaged in peptide bonds. This study shows that externally induced changes in the intramolecular bonding, e.g., by coordination, conformation geometry or hydrogen-bonding, can significantly influence the S K-edge spectra, and emphasizes the importance of a similar chemical surrounding when choosing the model compounds for standard spectra of sulfur functional groups, used to deconvolute composite experimental spectra.

  • 29. Risberg, Emiliana Damian
    et al.
    Mink, János
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Abbasi, Alireza
    Skripkin, Mikhail Yu.
    Hajba, Laszló
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Lindqvist-Reis, Patric
    Bencze, Éva
    Sandström, Magnus
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Ambidentate coordination in hydrogen bonded dimethyl sulfoxide, (CH3)2SO H3O+, and in dichlorobis(dimethyl sulfoxide) palladium(II) and platinum(II) solid solvates, by vibrational and sulfur K-edge X-ray absorption spectroscopy2009In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, p. 1328-1339Article in journal (Refereed)
    Abstract [en]

     

    The strongly hydrogen bonded species (CH3)2SOH3O+ formed in concentrated hydrochloric acid displays a new low energy feature in its sulfur K-edge X-ray absorption near edge structure (XANES) spectrum. Density Functional Theory-Transition Potential (DFT-TP) calculations reveal that the strong hydrogen bonding decreases the energy of the transition S(1s) → LUMO, which has antibonding σ*(S–O) character, with about 0.8 eV. Normal coordinate force field analyses of the vibrational spectra show that the SO stretching force constant decreases from 4.72 N cm−1 in neat liquid dimethyl sulfoxide to 3.73 N cm−1 for the hydrogen bonded (CH3)2SOH3O+ species. The effects of sulfur coordination on the ambidentate dimethyl sulfoxide molecule were investigated for the trans-Pd((CH3)2SO)2Cl2, trans-Pd((CD3)2SO)2Cl2 and cis-Pt((CH3)2SO)2Cl2 complexes with square planar coordination of the chlorine and sulfur atoms. The XANES spectra again showed shifts toward low energy for the transition S(1 s) → LUMO, now with antibonding σ*(M–Cl, M–S) character, with a larger shift for M = Pt than Pd. DFT-TP calculations indicated that the differences between the XANES spectra of the geometrical cis and trans isomers of the M((CH3)2SO)2Cl2 complexes are expected to be too small to allow experimental distinction. The vibrational spectra of the palladium(II) and platinum(II) complexes were recorded and complete assignments of the fundamentals were achieved. Even though the M–S bond distances are quite similar the high covalency especially of the Pt–S bonds induces significant increases in the S–O stretching force constants, 6.79 and 7.18 N cm−1, respectively.

  • 30.
    Selander, Nicklas
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis and transformation of organoboronates and stannanes by pincer-complex catalysts2009In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, no 32, p. 6267-6279Article in journal (Refereed)
  • 31.
    Shatskiy, Andrey
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lomoth, Reiner
    Abdel-Magied, Ahmed F.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Nuclear Materials Authority, Egypt.
    Rabten, Wangchuk
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Laine, Tanja M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Chen, Hong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). KTH Royal Institute of Technology, Sweden.
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Andersson, Pher G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Catalyst-solvent interactions in a dinuclear Ru-based water oxidation catalyst2016In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 45, no 47, p. 19024-19033Article in journal (Refereed)
    Abstract [en]

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

  • 32.
    Siegbahn, Per
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Blomberg, Margareta
    Stockholm University, Faculty of Science, Department of Physics.
    The Combined Picture from Theory and Experiments on Water Oxidation, Oxygen Reduction and Proton Pumping2009In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, no 30, p. 5832-5840Article in journal (Refereed)
    Abstract [en]

     

    In order to illustrate how theory and experiments can be combined, examples are taken from two projects that have been going on for a decade. The goal is to obtain the full mechanistic picture of wateroxidation in photosystem II and proton pumping in cytochrome c oxidase. It is argued that for obtaining a complete description of these processes, both experiments and theoretical calculations are needed. It is obvious that there are aspects, which are out of reach for computations, but there are also key aspects that can not be obtained by experiments. This concerns very short-lived species but also, in the case of photosynthesis in particular, structural information that is presently out of reach. The main contributions from theory in the present cases, is for photosynthesis a mechanism for O–O bond formation including new and improved structures for all S-states, and for proton pumping a plausible and simple mechanism for proton gating. The examples also illustrate that sometimes rather qualitative experimental information can be of highest importance.

  • 33.
    Siegbahn, Per E. M.
    Stockholm University, Faculty of Science, Department of Physics.
    Water oxidation in photosystem II: oxygen release, proton release and the effect of chloride2009In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, no 45, p. 10063-10068Article in journal (Refereed)
    Abstract [en]

    Recent reviews on quantum chemical studies of water oxidation in photosystem II have focused on the energetics of O-O bond formation, including the energies of the different S-states. In the present paper, this is extended by discussing the release pathways for dioxygen and protons from the oxygen evolving complex. Based on recent X-ray structures, the effect of adding chloride has also been investigated. Unlike most earlier suggestions, a small, but probably significant, electrostatic effect of adding chloride is found for the higher S-states. For releasing dioxygen in the S-4-state, entropy plays a major role. The suggested pathway for proton release in the S-1 to S-2 transition involves key roles of an outside water and the motion of Asp170. An electron transfer between manganese centra during proton release is also found to be important for a low barrier.

  • 34.
    Stewart, Beverly
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nyhlén, Jonas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martin-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Privalov, Timofei
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    A computational study of the CO dissociation in cyclopentadienyl ruthenium complexes relevant to the racemization of alcohols2013In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 42, no 4, p. 927-934Article in journal (Refereed)
    Abstract [en]

    The formation of an active 16-electron ruthenium sec-alkoxide complex via loss of the CO ligand is an important step in the mechanism of the racemization of sec-alcohols by (eta(5)-Ph5C5) Ru(CO)(2)X ruthenium complexes with X = Cl and OtBu. Here we show with accurate DFT calculations the potential energy profile of the CO dissociation pathway for a series of relevant (eta(5)-Ph5C5) Ru(CO) 2X complexes, where X = Cl, OtBu, H and (COOBu)-Bu-t. We have found that the CO dissociation energy increases in the following order: OtBu (lowest), Cl, COOtBu and H (highest). Using the distance between ruthenium and C-CO, r = Ru-C-CO, as a constraint, and by optimizing all other degrees of freedom for a range of Ru-CO distances, we obtained relative energies, Delta E(r) and geometries of a sufficient number of transient structures with the elongated Ru-CO bond up to r = 3.4 angstrom. Our calculations provide a quantitative understanding of the CO ligand dissociation in (eta(5)-Ph5C5) Ru(CO)(2)Cl and (eta(5)-Ph5C5) Ru(CO) 2(OtBu) complexes, which is relevant to the mechanism of their catalytic activity in the racemization of alcohols. We recently reported that exchange of the CO ligand by isotopically labeled (CO)-C-13 in the Ru-(OBu)-Bu-t complex occurs twenty times faster than that in the Ru-Cl complex. This corresponds to a difference of 1.8 kcal mol(-1) in the CO dissociation energy (at room temperature). This is in very good agreement with the calculated difference between the two potential energy curves for Ru-OtBu and Ru-Cl complexes, which is about 1.8-2 kcal mol(-1) around the corresponding transition states of the CO dissociation. The calculated difference in the total energy for CO dissociation in (eta(5)-Ph5C5) Ru(CO)(2)X complexes is related to the stabilization provided by the X group in the final 16-electron complexes, which are formed via product-like transition states. In addition to the calculated transition states of CO dissociation in Ru-OtBu and Ru-Cl complexes, the calculated transient structures with the elongated Ru-CO bond provide insight into how the geometry of the ruthenium complex with a potent heteroatom donor group (X) gradually changes when one of the COs is dissociating.

  • 35.
    Su, Jie
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Wang, Yingxia
    Lin, Jianhua
    Liang, Jie
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    A silicogermanate with 20 ring channels directed by a simple quaternary ammonium cation2013In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 42, no 5, p. 1360-1363Article in journal (Refereed)
    Abstract [en]

    A silicogermanate, PKU-12, with the -CLO type of zeolite framework was hydrothermally synthesized under fluoride media using diisopropylethylmethylammonium as a structure directing agent. The formation of the silicogermanate zeolite with 20-ring channels has not only extended the -CLO family from phosphates into silicogermanates, but also demonstrated its structural diversity.

  • 36.
    Sun, Junliang
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Structure determination of porous materials by electron crystallography2010In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 39, p. 8355-8362Article, review/survey (Refereed)
    Abstract [en]

    Structure determination of porous materials is important for understanding the materials properties and exploiting their applications. Compared to X-ray diffraction, electron crystallography has two unique advantages. Crystals that are too small to be studied by X-ray diffraction can be studied by electron crystallography. The structure factor phase information, which is lost in diffraction, can be obtained from high resolution transmission electron microscopy (HRTEM) images. Here we will present different techniques and applications of electron crystallography for structure determination of zeolites and ordered mesoporous materials, based on electron diffraction data and/or HRTEM images. Electron crystallography and X-ray diffraction are complementary in many aspects. Their combinations show great potentials for structure determination of complex porous materials.

  • 37.
    Sun, Junliang
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Structure determination of zeolites and ordered mesoporous materials by electron crystallography2010In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 39, no 36, p. 8355-8362Article in journal (Refereed)
    Abstract [en]

    Structure determination of porous materials is important for understanding the materials properties and exploiting their applications. Compared to X-ray diffraction, electron crystallography has two unique advantages. Crystals that are too small to be studied by X-ray diffraction can be studied by electron crystallography. The structure factor phase information, which is lost in diffraction, can be obtained from high resolution transmission electron microscopy (HRTEM) images. Here we will present different techniques and applications of electron crystallography for structure determination of zeolites and ordered mesoporous materials, based on electron diffraction data and/or HRTEM images. Electron crystallography and X-ray diffraction are complementary in many aspects. Their combinations show great potentials for structure determination of complex porous materials.

  • 38. Szijjarto, Csongor
    et al.
    Pershagen, Elias
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Borbas, K. Eszter
    Functionalisation of lanthanide complexes via microwave-enhanced Cu(I)-catalysed azide–alkyne cycloaddition2012In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 41, no 25, p. 7660-7669Article in journal (Refereed)
    Abstract [en]

    Cu-I-catalysed azide-alkyne cycloaddition reactions were used to functionalise lanthanide(III)-complexes (Ln; La, Eu and Tb) incorporating alkyne or azide reactive groups. Microwave irradiation significantly accelerated the reactions, enabling full conversion to the triazole products in some cases in 5 min. Alkyl and aryl azides and alkyl and aryl alkynes could all serve as coupling partners. These reaction conditions proved efficient for cyclen-tricarboxylates and previously unreactive cyclen-tris-primary amide chelates. The synthesis of heterobimetallic (Eu/Tb, EuTb17 and Eu/La, EuLa17) and heterotrimetallic (Eu/La/Eu) complexes was achieved in up to 60% isolated yield starting from coumarin 2-appended alkynyl complexes Tb16 or La16 and an azido-Eu complex Eu4, and bis-alkynyl La-complex La5 and Eu4, respectively. EuTb17 displayed dual Eu-III and Tb-III-emission upon antenna-centred excitation.

  • 39. Wei, Qi
    et al.
    Zhang, Ya-Jun
    Song, Ying
    Yang, Guo-Yu
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    A series of inorganic-organic hybrid cadmium borates with novel Cd-centred [Cd@B14O20(OH)(6)](2-) clusters2016In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 45, no 35, p. 13937-13943Article in journal (Refereed)
    Abstract [en]

    Four novel inorganic-organic hybrid cadmium borates, namely [EAH](2){(py)(2)Cd@[B14O20-(OH)(6)]} (1, py = pyridine, EA = ethylamine), [PAH](2){(py)(2)Cd@[B14O20(OH)(6)]} (2, PA = propylamine), [pyH](2){(py)(2)Cd@ [B14O20(OH)(6)]} (3) and {(AImH)(2)Cd@[B14O20(OH)(6)]} (4, AIm = 1-(3-aminopropyl) imidazole) have been solvothermally synthesized and characterized by elemental analysis, thermogravimetric analysis, IR spectroscopy, UV-Vis-NIR spectroscopy, fluorescence spectroscopy, powder X-ray diffraction, and single-crystal X-ray diffraction, respectively. They represent the first hybrid cadmium borates that exhibit 3D supramolecular open-frameworks with different topologies. All the networks are formed by the unprecedented Cd-centred cluster [Cd@B14O20(OH)(6)](2-), and further link each other via a multipoint H-bond system. UV-Vis-NIR spectral investigation reveals that these borates are wide-band-gap semiconductors. Moreover, they display strong fluorescence emission around 430 nm, making them excellent candidates for optoelectronic applications as blue materials.

  • 40.
    Willhammar, Tom
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Mayoral, Alvaro
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    3D reconstruction of atomic structures from high angle annular dark field (HAADF) STEM images and its application on zeolite silicalite-12014In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 43, no 37, p. 14158-14163Article in journal (Refereed)
    Abstract [en]

    High-resolution transmission electron microscopy (HRTEM) has shown to be very powerful for solving three-dimensional (3D) structures of unknown crystals. HRTEM has a unique advantage over diffraction for solving structures. Crystallographic structure factor phases, which are lost in diffraction can be directly obtained from HRTEM images. For the determination of a 3D crystalline structure by HRTEM, the crystallographic structure factor amplitudes and phases extracted from HRTEM images along different zone axes are combined to reconstruct a 3D electrostatic potential map. In recent years, scanning transmission electron microscopy (STEM) has reached the atomic resolution, which is comparable to that of HRTEM. Here we show, for the first time, that the structure factor phases can be also obtained from high angle annular dark-field (HAADF)-STEM images and used for 3D reconstruction of atomic structures. This is applied to the complex zeolite structure, silicalite-1 (Formula SiO2, framework code MFI, Pnma, a = 20.090 angstrom, b = 19.738 angstrom and c = 13.142 angstrom). We have compared the amplitudes and phases obtained from HAADF-STEM images with those from HRTEM images.

  • 41.
    Xu, Chao
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Anhui University of Technology, China.
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Shi, Hua-Tian
    Xina, ZhiFeng
    Zhang, Qian-Feng
    Stepwise assembly of a semiconducting coordination polymer [Cd8S(SPh)(14)(DMF)(bpy)](n) and its photodegradation of organic dyes2015In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 44, no 14, p. 6400-6405Article in journal (Refereed)
    Abstract [en]

    Chalcogenolate clusters can be interlinked with organic linkers into semiconducting coordination polymers with photocatalytic properties. Here, discrete clusters of Cd8S(SPh)(14)(DMF)(3) were interlinked with 4,4'-bipyridine into a one dimensional coordination polymer of [Cd8S(SPh)(14)(DMF)(bpy)](n) with helical chains. A stepwise mechanism for the assembly of the coordination polymer in DMF was revealed by an ex situ dynamic light scattering study. The cluster was electrostatically neutral and showed a penta-supertetrahedral structure. During the assembly each cluster was interlinked with two 4,4'-bipyridine molecules, which replaced the two terminal DMF molecules of the clusters. In their solid-state forms, the cluster and the coordination polymer were semiconductors with wide band gaps of 3.08 and 2.80 ev. They photocatalytically degraded rhodamine B and methylene blue in aqueous solutions. The moderate conditions used for the synthesis could allow for further in situ studies of the reaction-assembly of related clusters and coordination polymers.

  • 42. Yang, Tao
    et al.
    Petricek, Vaclav
    Wan, Wei
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Wei, Zidong
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Mullite-derivative Bi2MnxAl7-xO14 (x similar to 1): structure determination by powder X-ray diffraction from a multi-phase sample2012In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 41, no 10, p. 2884-2889Article in journal (Refereed)
    Abstract [en]

    As a supplementary method to single crystal X-ray diffraction (XRD), nowadays crystal structure determination by powder XRD has become popular, especially for those areas with difficulties getting high quality single crystals. Here we observed an intermediate phase Bi2MnxAl7-xO14 (x similar to 1) during the decomposition of mullite-Bi2MnxAl4-xO9+delta (solid solution of Bi2Mn4O10-Bi2Al4O9). As a metastable phase, it started to decompose while forming, thus no single-phase sample can be obtained. We successfully determined its structure by powder XRD from a multi-phase sample. A modified Le Bail fitting using the atomic structure information of known impurities showed a more reliable intensity extraction from a multi-phase powder XRD than that without using atomic structures for the known impurities. The charge-flipping algorithm and Monte-Carlo based simulated annealing technique were then applied to obtain the full structural model. In principle, this strategy is applicable to more complex problems, and not limited to the oxide materials. Bi2MnxAl7-xO14 possesses a mullite-related structure. There are one tetrahedral and two octahedral sites for Mn and Al, where disordering with substantial site preferences is observed. Specifically, M1O(6) and M3O(6) octahedra share edges along the c-direction with the periodicity of 1 : 2. These octahedral chains are further connected into a 3D structure through M2O(4) dimmers and Bi.

  • 43.
    Zhang, Dong
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Johnsson, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Lidin, Sven
    Kremer, Reinhard K.
    The new nickel tellurite chloride compound ni15te12o34cl10 synthesis, crystal structure and magnetic properties2013In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 42, no 5, p. 1394-1399Article in journal (Refereed)
    Abstract [en]

    A new nickel tellurite oxohalide, Ni15Te12O34Cl10, has been prepared by chemical vapour transport reactions and the crystal structure was determined by single-crystal X-ray diffraction. The compound crystallizes in the triclinic space group P (1) over bar with the pseudomonoclinic cell parameters a = 10.3248(6) angstrom, b = 10.3249(6) angstrom, c = 11.6460(8) angstrom, alpha = 73.782(6)degrees, beta = 73.782(6)degrees, gamma = 63.51(2)degrees, Z = 1, R-1 = 0.0264. The Ni2+ ions have octahedral [NiO6] and [NiO4Cl2] coordinations, the Te4+ ions have one-sided [TeO3] and [TeO4] coordinations. The crystal structure can be described as consisting of nickel oxide ribbons extending along (001) that are connected by corner sharing [TeO3] and [TeO4] groups to build the open framework structure. The chlorine atoms and the Te-lone pairs are facing voids in the oxide framework. The new compound undergoes two successive antiferromagnetic ordering transitions at similar to 50 K and similar to 10 K. The Curie-Weiss temperature obtained from detailed evaluation of the high-temperature magnetic susceptibilities is positive indicating predominant ferromagnetic superexchange interactions between the Ni magnetic moments.

  • 44.
    Zheng, Haoquan
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Su, Jie
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Gao, Feifei
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ultra-small mesoporous silica nanoparticles as efficient carriers for pH responsive releases of anti-cancer drugs2015In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 44, no 46, p. 20186-20192Article in journal (Refereed)
    Abstract [en]

    Mesoporous silica has emerged as one of the most promising carriers for drug delivery systems. However, the synthesis of ultra-small mesoporous silica nanoparticles (UMSNs) and their application in drug delivery remains a significant challenge. Here, spherical UMSNs (similar to 25 nm) have been synthesized and tested as drug carriers. Anti-cancer drugs mitoxantrone (MX), doxorubicin (DOX) and methotrexate (MTX) have been utilized as model drugs. The pH-responsive drug delivery system can be constructed based on electrostatic interactions between carriers and drug molecules. The UMSNs could store drugs under physiological conditions and release them under acidic conditions. Different pH-responsive release profiles were obtained in phosphate buffer solutions (PBSs) at the designed pH values (from 4.0 to 7.4). MX and DOX can be used in the pH-responsive delivery system, while MTX cannot be used. Furthermore, we found that the physiological stabilities of these drug molecules in UMSNs are in a decreasing order MX > DOX > MTX, which follows the order of their isoelectric point (pI) values.

  • 45.
    Zimmermann, Iwan
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Corgnet, Alexis
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Johnsson, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lidin, Sven
    Synthesis and crystal structure of a series of incommensurately modulated composite oxohalide compounds2014In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 43, no 42, p. 15812-15817Article in journal (Refereed)
    Abstract [en]

    Transparent, needle-like single crystals of the isostructural compounds [Sb4O7+3 delta X4][Zn-3](1+delta) = CL Br, I) delta approximate to 0.2 were obtained from chemical reactions in evacuated and sealed silica tubes. First, the average structure was solved in P211n but the model refined poorly and a lowering of the symmetry to the 3 + 1 dimensional space group P2(1)(alpha 0 gamma)0 gave a significantly better fit to the data. This model used second order positional modulations for all the atoms. Whereas Sb, Cl (Br, I) and most 0 positions were well behaved, there was a mismatch with Zn that was better described in a sub-cell, thus yielding a composite structure. The composite nature of the structure leads to a charge imbalance that is compensated by oxygen vacancies.

  • 46.
    Zimmermann, Iwan
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kremer, Reinhard K.
    Hu, Shichao
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Johnsson, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Synthesis, crystal structure and magnetic properties of a new copper oxo-antimony sulphate CuSb6O8(SO4)(2)2016In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 45, no 1, p. 392-396Article in journal (Refereed)
    Abstract [en]

    The new copper oxo-antimony sulphate CuSb6O8(SO4)(2) crystallizes in the triclinic space group P (1) over bar with the unit cell parameters a = 5.5342(4) angstrom, b = 7.6706(6) angstrom, c = 9.2374(7) angstrom, alpha = 96.505(5)degrees, beta = 93.818(4)degrees, gamma = 109.733(4)degrees and Z = 1. The crystal structure is made up of layers stacking along [001]. The layers are charge neutral and are connected to each other by only weak interactions. The copper atoms adopt a square planar [CuO4] coordination and such units are well separated from each other by corner and edge sharing to [SbO4] building blocks. The latter polymerize to form sheets with the formula [Sb3O8](infinity). Sulphate groups connect to the antimony oxide sheets by corner sharing and are located at the interface of the layers. Above similar to 10 K the magnetic susceptibility follows very well a Curie-Weiss law whereas below 10 K increasing deviations indicate the onset of antiferromagnetic correlations. Fitting the data in the range 10-50 K yields a Curie-Weiss temperature theta of -2.25(5) K. A sharp anomaly centered at T-C = 0.67 K in the heat capacity data indicates long-range magnetic ordering. Short range antiferromagnetic correlations well above T-C are seen in the magnetic contribution to the heat capacity and the magnetic susceptibility. These can be well described by the magnetism of a spin S = 1/2 Heisenberg chain with the nearest neighbor antiferromagnetic spin exchange interaction of J(intra) = similar to 2.8 K.

  • 47.
    Zimmermann, Iwan
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kremer, Reinhard K.
    Reuvekamp, Patrick
    Johnsson, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Crystal structure and magnetic properties of Cr3Te5O13Cl32013In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 42, no 24, p. 8815-8819Article in journal (Refereed)
    Abstract [en]

    A new chromium tellurite oxochloride, Cr3Te5O13Cl3, has been prepared by solid-state reaction and the crystal structure was determined by single crystal X-ray diffraction. The compound crystallizes in the non-centrosymmetric space group P2(1)2(1)2(1) with the unit cell a = 4.90180(10) angstrom, b = 17.3394(2) angstrom, c = 17.5405(2) angstrom, Z = 4, R-1 = 0.0282. The Cr3+ ions have octahedral [CrO6] oxygen coordination, the Te4+ ions have one sided [TeO3] and [TeO3Cl] coordinations. The [CrO6] octahedra are edge sharing and form chains extending along [100]. These are connected by corner sharing [TeO3] and [TeO3Cl] groups to form layers parallel to (110). The layers are connected by weak interactions in between Te4+ in the layers and Cl- ions located in between. The compound undergoes antiferromagnetic ordering at similar to 34 K with a Weiss constant of -230 K. Isothermal magnetization measurements reveal a critical field of about 0.25 T above which the magnetization versus field changes from linear to a Brillouin-like saturation behaviour. The frustration ratio amounts to similar to 6.8 indicative of sizable competing antiferromagnetic spin-exchange interaction. The dielectric constant epsilon (6 kHz) amounts to similar to 7.9 and decreases by about 1% on cooling from 50 K to liquid helium temperatures.

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