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  • 1.
    Hu, Shichao
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Transition metal oxofluorides comprising lone pair elements: Synthesis and Characterization2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Within the family of transition metal oxochlorides/bromides containing lone pair elements, the transition metal cations often adopt a low-dimensional arrangement such as 2D layers, 1D chains or 0D clusters. The reduced dimensionality is attributed to the presence of stereochemically active lone pairs which are positioned in the non-bonding orbital and will not participate in bond formation and instead act as structural spacers that help to separate coordination polyhedra around transition metal cations from forming three dimensional networks. On the other hand, the chlorine and bromine ions also play an important role to open up the crystal structure because of their low coordination number. However, fluorine has been rarely used in this concept due to the difficulties in synthesis.

    This thesis is focused on finding new compounds in the M-L-O-F system (M = transition metal cation, L= p-block lone pair elements such as Te4+, Se4+, or Sb3+) in order to study the structural character of fluorine. Hydrothermal reactions have been adopted instead of conventional chemical transport reactions that are commonly used for synthesizing compounds in the M-L-O-(Cl, Br) family. A total of 8 new transition metal oxofluorides containing lone pair elements have been synthesized and their structures have been determined via single crystal X-ray diffraction. Bond valence sum calculations are used to distinguish in between fluorine and oxygen due to their very similar X-ray scattering factors.

  • 2.
    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.

  • 3.
    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.

  • 4.
    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).
    Law, Joseph M.
    Bettis, Jerry L. Jr.
    Whangbo, Myung-Hwan
    Kremer, Reinhard K.
    Crystal Structure and Magnetic Properties of FeSeO3F: Alternating Antiferromagnetic S = 5/2 chains2014In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 53, no 8, p. 4250-4256Article in journal (Refereed)
    Abstract [en]

    The new oxofluoride FeSeO3F crystallizes in the space group P21/n and consists of [FeO3F]∞ zigzag chains with alternating Fe−F−Fe and Fe−O−Fe spin exchange paths. The magnetic susceptibility of FeSeO3F is largely described by an S = 5/2 Heisenberg antiferromagnetic chain with alternating antiferromagnetic spin exchanges, and FeSeO3F undergoes a long-range antiferromagnetic ordering below 45 K.

  • 5.
    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).
    Lemmens, P.
    Schmid, D.
    Menzel, D.
    Tapp, J.
    Möller, A.
    Acentric Pseudo-Kagome Structures: The Solid Solution (Co1-xNix)3Sb4O6F6Manuscript (preprint) (Other academic)
  • 6.
    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).
    Lemmens, Peter
    Schmid, Daniel
    Menzel, Dirk
    Tapp, Joshua
    Moeller, Angela
    Acentric Pseudo-Kagome Structures: The Solid Solution (Co1-xNix)(3)Sb4O6F62014In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 26, no 12, p. 3631-3636Article in journal (Refereed)
    Abstract [en]

    Compounds within the solid solution (Co1-xNix)(3)Sb4O6F6 were prepared by the hydrothermal method. The compounds crystallize in the noncentrosymmetric cubic space group I (4) over bar 3m with unit cell parameters a = 8.176(1) angstrom for M = Co and a = 8.0778(1) angstrom for M = Ni. The crystal structure is made up by corner sharing [MO2F4] octahedra via the fluorine atoms. [Sb4O6E4] supertetrahedra (T2) consisting of four [SbO3E] groups (E being the stereo-chemically active lone-pair on Sb) that share O atoms with the [MO2F2](n) network. Magnetic ordering phenomena are observed with two characteristic temperatures, T-N and T*, in the range from 67 to 170 K, that evolve gradually with composition and collapse for M = Co (x = 0) to one transition. T-N is assigned to a transition into a long-range ordered antiferromagnetic phase, and T* marks a temperature in the range of 45 to 65 K where field cooled (FC) and zero field cooled (ZFC) susceptibility splits. The latter is tentatively attributed to a canting of the spin moments.

  • 7.
    Hu, Shichao
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Mace, Amber
    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).
    Gnezdilov, Vladimir
    Lemmens, Peter
    Tapp, Joshua
    Möller, Angela
    Crystal Structure and Magnetic Properties of the S=1/2 Quantum Spin System Cu-7(TeO3)(6)F-2 with Mixed Dimensionality2014In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 53, no 14, p. 7661-7667Article in journal (Refereed)
    Abstract [en]

    The new oxofluoride Cu-7(TeO3)(6)F-2 has been synthesized by hydrothermal synthesis. It crystallizes in the triclinic system, space group P (1) over bar. The crystal structure constitutes a Cu-O framework with channels extending along [001] where the F- ions and the stereochernically active lone-pairs on Te4+ are located. From magnetic susceptibility, specific heat, and Raman scattering measurements we find evidence that the magnetic degrees of freedom of the Cu-O-Cu segments in Cu-7(TeO3)(6)F-2 lead to a mixed dimensionality with single Cu S = 1/2 moments wealdy coupled to spin-chain fragments. Due to the weaker coupling of the single moments, strong fluctuations exist at elevated temperatures, and long-range magnetic ordering evolves at comparably low temperatures (T-N = 15 K).

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