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  • 1.
    Abdelhamid, Hani Nasser
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Assiut University, Egypt.
    Wilk-Kozubek, Magdalena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). PORT Polish Center for Technology Development, Poland.
    El-Zohry, Ahmed M.
    Gómez, Antonio Bermejo
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Valiente, Alejandro
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Martín-Matute, Belén
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Zou, Xiaodong
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Luminescence properties of a family of lanthanide metal-organic frameworks2019Inngår i: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 279, s. 400-406Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two isostructural series of lanthanide metal-organic frameworks denoted as SUMOF-7II (Ln) and SUMOF-7IIB (Ln) (Ln = La, Ce, Pr, Nd, Sm, Eu, and Gd) were synthesized using4,4',4 ''-(pyridine-2,4,6-triyl)tris(benzoic acid) (H(3)L2) and a mixture of H(3)L2 and 4,4',4 ''-(benzene-1,3,5-triyl)tris(benzoic acid) (H3BTB) as linkers, respectively. Both series were characterized using powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermal analysis (TGA), and photoluminescence spectroscopy. Photoluminescence measurements show that Eu-MOFs demonstrate a red emission while Pr- and Nd-MOFs display an emission in the near-infrared (NIR) range. On the other hand, La-, Ce-, Sm- and Gd-MOFs exhibit only a ligand-centered emission. The average luminescence lifetimes in the SUMOF-7IIB series are 1.3-1.4-fold longer than the corresponding ones in the SUMOF-7II series. SUMOF-7IIs show a good photo- and thermal stability. Altogether, the properties of SUMOF-7II and SUMOF-7IIB render them promising materials for applications including sensing, biosensing, and telecommunications.

  • 2.
    Abdelhamid, Hani
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Wilk-Kozubek, Magdalena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Ahmed, M. El-Zohry
    Valiente, Alejandro
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bermejo-Gomez, Antonio
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Martín-Matute, Belén
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Zou, Xiaodong
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Luminescence Properties for a Family of Highly Stable Lanthanide Metal-Organic FrameworksManuskript (preprint) (Annet vitenskapelig)
  • 3. Alammar, Tarek
    et al.
    Hamm, Ines
    Grasmik, Viktoria
    Wark, Michael
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Iowa State University, United States; U.S. Department of Energy, United States; Ruhr-Universität Bochum, Germany.
    Microwave-Assisted Synthesis of Perovskite SrSnO3 Nanocrystals in Ionic Liquids for Photocatalytic Applications2017Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 56, nr 12, s. 6920-6932Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nanosized SrSnO3 photocatalysts have been successfully synthesized by microwave synthesis in various ionic liquids (ILs) followed by a heat treatment process to optimize the materials' crystallinity. The influence of the ILs with various cations such as 1-butyl-3-methylimidazolium ([C(4)mim](+)), 6-bis(3-methylimidazolium-1-yl)hexane ([C-6(mim)(2)](2+)), butylpyridinium ([C4Py](+)), and tetradecyltrihexylphosphonium ([P-66614](+)) and bis(trifluoromethanesulfonyl)amide ([Tf2N](-)) as the anion on the structure, crystallization, and morphology of the products was investigated. The samples were characterized by X-ray diffraction (XRD), thermogravimetry (TG), scanning electron microscopy (SEM), surface area analysis by gas adsorption, X-ray photoelectron spectroscopy (XPS), diffuse reflectance UV vis spectroscopy, and Raman and IR spectroscopy. According to structure characterization by XRD and Raman spectroscopy all samples wcrystallized phase-pure in the orthorhombic GdFeO3 perovskite structure type. SEM reveals that, on the basis of the IL, th(e) obtained SrSnO3 nanoparticles exhibit different morphologies and sizes. Rod-shaped particles are formed in [C(4)minn][Tf2N], [C-6(mim)(2)][Tf2N](2), and p [P-66614][Tf2N]. However, the particle dimensions and size distribution vary depending on the IL and range from quite thin and long needlelike partinles with a narrow size distribution obtained in [P-66614] [TfA to relatively larger particles with a broader size distribution obtained in [C-6(mim)(2)][Tf2N](2). In contrast, in [C4Py][Tf2N] nanospheres with a diameter of about 50 nm form. For these particles the highest photocatalytic activity was observed. Our investigations indicate that the improved photocatalytic activity of this material results from the synergistic effect of the relatively large surface area associated with nanosize and an appropriate energy band structure.

  • 4. Alammar, Tarek
    et al.
    Hlova, Ihor Z.
    Gupta, Shalabh
    Balema, Viktor
    Pecharsky, Vitalij K.
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Iowa State University, USA.
    Luminescence properties of mechanochemically synthesized lanthanide containing MIL-78 MOFs2018Inngår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 47, nr 22, s. 7594-7601Artikkel i tidsskrift (Fagfellevurdert)
    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. Bell, Thomas
    et al.
    Celania, Chris R.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Smetana, Volodymyr
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Meyer, Gerd
    Tb3Pd2, Er3Pd2 and Er6Co5-x: structural variations and bonding in rare-earth-richer binary intermetallics2018Inngår i: Acta crystallographica. Section C, Structural chemistry, ISSN 2053-2296, Vol. 74, nr 9, s. 991-996Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The three binary Tb/Er-rich transition metal compounds Tb3Pd2 (triterbium dipalladium), Er3Pd2 (trierbium dipalladium) and Er6Co5-x (hexaerbium pentacobalt) crystallize in the space groups Pbam (Pearson symbol oP20), P4/mbm (tP10) and P6(3)/m (hP22), respectively. Single crystals of Tb3Pd2 and Er6Co5-x suitable for X-ray structure analysis were obtained using rare-earth halides as a flux. Tb3Pd2 adopts its own structure type, which can be described as a superstructural derivative of the U3Si2 type, which is the type adopted by Er3Pd2. Compound Er6Co5-x belongs to the Ce6Co2-xSi3 family. All three compounds feature fused tricapped {TR6} (R = rare-earth metal and T = transition metal) trigonal prismatic heterometallic clusters. R3Pd2 is reported to crystallize in the U3Si2 type; however, our more detailed structure analysis reveals that deviations occur with heavier R elements. Similarly, Er6Co5-x was assumed to be stoichiometric Er4Co3 = Er6Co4.5. Our studies reveal that it has a single defective transition-metal site leading to the composition Er6Co4.72(2). LMTO (linear muffin-tin orbital)-based electronic structure calculations suggest the strong domination of heteroatomic bonding in all three structures.

  • 6.
    Celania, Chris
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Structures, properties, and potential applications of rare earth-noble metal tellurides2019Inngår i: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 274, s. 243-258Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    As many nations continue to develop and industrialize, the global energy demands are rising rapidly. With the threat of climate change disaster looming, the search for sustainable, green energy has become of higher priority. Thermoelectric materials add an important facet to the mosaic of future energy plans by allowing the scavenging of (low-quality waste) heat created through other processes and their transformation back into useful electrical energy. Thermoelectrics (similar to other green energy sources like solar cells) have struggled to reach high enough efficiencies to allow their cost-effective widespread implementation. Thus, the search for new thermoelectric materials has gained momentum. This review covers the growing family of rare earth metal (R: Sc, Y, and La-Lu)-noble metal (M: Cu, Ag, Au, Pd and Pt)-tellurides which are an interesting group of materials in the discussed context. Rare earth metal -noble metal tellurides constitute an increasing family of structures, numbering nearly forty unique structure types and including quaternary and quinary compounds. Structures include 1D channel structures, 2D layered slab structures, and complex 3D networks. R-M-Te compounds provide a wide variety of p-type semiconducting materials to choose from. The effectiveness of these structures as thermoelectric materials range in utility, with most showing maximum performance (figure of merit, zT - see below) values in the mid to high temperature ranges. To date, this culminates in the highest zT for this family with TbCuTe2, zT = 1.0 at 750 K, which still has potential for optimization. Albeit most observed compounds have been structurally quite well characterized, for many a thorough investigation of their physical properties, be it transport or magnetism is lacking. This work strives to combine, analyze, and at times untangle the variety of structures and properties reported across the breadth of research on this family.

  • 7. Celania, Chris
    et al.
    Smetana, Volodymyr
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Iowa State University, USA.
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Iowa State University, USA.
    Bringing order to large-scale disordered complex metal alloys: Gd2Au15-xSbx and BaAuxGa12-x2018Inngår i: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 20, nr 3, s. 348-355Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Herein, two new tetragonal complex metallic alloys (CMAs) have been discovered and characterized: Gd2Au15-xSbx [x = 3.0-3.6; I4/mmm; tI34; a = 7.31-7.33 angstrom, c = 14.05-14.11 angstrom; V = 750.2-758 angstrom(3)] and BaAuxGa12-x [x = 3.6-4.4; I4/mcm; tI104; a = 8.77-8.78 angstrom, c = 26.06-26.13 angstrom; V = 2006.5-2010 angstrom(3)]. Both structures incorporate significant anionic site mixing and intricate positional disorder. Gd2Au15-xSbx represents a new structure type with in-plane disordered, but strongly geometrically restricted rhombi motifs. These rhombi connect through additional mixed Au/Sb positions along the c axis; this forms octahedral fragments. BaAuxGa12-x finds its place within the extended NaZn13 structural family, displaying cation-centered snub cubes with empty, distorted icosahedra (allowing for the 1 : 12 ratio) and tetrahedral stars. The split positions order due to geometric constraints to form nets of crown cyclooctane-like sheets in two different conformations. Adjacent planes adopt opposite conformations, forming layers of snub cubes with order between layers, but disorder across the greater structure. The substantial degree of mixing in both structures, together with mutual orientation of the ordered and disordered positions, suggests significant importance of heteroatomic bonding, typically found in polar intermetallic compounds.

  • 8. Celania, Chris
    et al.
    Smetana, Volodymyr
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Iowa State University, USA.
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Iowa State University, USA.
    Crystal structures and new perspectives on Y3Au4 and Y(14)Au512017Inngår i: Acta crystallographica. Section C, Structural chemistry, ISSN 2053-2296, Vol. 73, s. 692-696Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Y3Au4 (triyttrium tetragold) and Y14Au51 (tetradecayttrium henpentacontagold), two binary representatives of Au-rich rare earth (R) systems crystallize with the space groups R (3) over bar and P6/m, adopting the Pu3Pd4 and Gd14Ag51 structure types, respectively (Pearson symbols hR(42) and hP(65)). Avariety of binary R-Au compounds have been reported, although only a few have been investigated thoroughly. Many reports lack information or misinterpret known compounds reported elsewhere. The Pu3Pd4 type is fairly common for group 10 elements Ni, Pd, and Pt, while Au representatives are restricted to just five examples, i.e. Ca3Au4, Pr3Au4, Nd Au-3(4), Gd3Au4, and Th3Au4. Sm6Au7 is suspected to be Sm3Au4 due to identical symmetry and close unit-cell parameters. The Pu3Pd4 structure type allows for full substitution of the position of the rare earth atom by more electronegative and smaller elements, i.e. Ti and Zr. The Gd14Ag51 type instead is more common for the group 11 metals, while rare representatives of group 12 are known. Y3Au4 can be represented as a tunnel structure with encapsulated cations and anionic chains. Though tunnels are present in Y14Au51, this structure is more complex and is best described in terms of polyhedral 'pinwheels' around the tunnel forming polyhedra along the c axis.

  • 9. Celania, Chris
    et al.
    Smetana, Volodymyr
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). U.S. Department of Energy, United States.
    Provino, Alessia
    Manfrinetti, Pietro
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). U.S. Department of Energy, United States; Iowa State University, United States.
    R-14(Au, M)(51) (R = Y, La-Nd, Sm-Tb, Ho, Er, Yb, Lu; M = Al, Ga, Ge, In, Sn, Sb, Bi): Stability Ranges and Site Preference in the Gd14Ag51 Structure Type2018Inngår i: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 18, nr 2, s. 993-1001Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Twenty new ternary representatives of the Gd14Ag51 structure type have been synthesized within the R-Au-M family (R = Y, La-Nd, Sm-Tb, Ho, Er, Yb, Lu; M = Al, Ga, Ge, Sn, Sb, Bi) using solid state synthesis techniques. The list of post transition metals (M) involved in the formation of this type of structure could be augmented by five new representatives. All compounds crystallize in the hexagonal space group P6/m (#175) with the unit cell ranges of a = 12.3136(2)-12.918(1) angstrom and c = 8.9967(3)-9.385(1) angstrom, and incorporate different degrees of Au/M mixing. The involvement of the post transition element in the structure varies from one to another compound both qualitatively and quantitatively. A rather significant phase width can be expected for the majority of compounds, however, not without exclusions. The distribution of the post transition metals within the structure has been analyzed via single crystal X-ray diffraction. While the positional disorder of one near-origin Au position is expectable for all compounds due to steric reasons, two specimens show an obvious deviation from the others including another Au position split along the c axis. Possible factors affecting this behavior are discussed.

  • 10. Chand, Deepak
    et al.
    Wilk-Kozubek, Magdalena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Iowa State University, United States; US Department of Energy and Critical Materials Institute, United States; Łukasiewicz Research Network - PORT Polish Center for Technology Development, Poland.
    Smetana, Volodymyr
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). US Department of Energy and Critical Materials Institute, United States.
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Iowa State University, United States; US Department of Energy and Critical Materials Institute, United States; Łukasiewicz Research Network - PORT Polish Center for Technology Development, Poland.
    Alternative to the Popular Imidazolium Ionic Liquids: 1,2,4-Triazolium Ionic Liquids with Enhanced Thermal and Chemical Stability2019Inngår i: ACS sustainable chemistry & engineering, ISSN 2168-0485, Vol. 7, nr 19, s. 15995-16006Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Direct quaternization of 1-methyl-1,2,4-triazole with n-alkyl methanesulfonates (alkyl = butyl, octyl, dodecyl) showed to be an atom-economic, convenient, mild, solvent- and halide-free way to obtain 1,2,4-triazolium methanesulfonate ionic liquids in high purity and yield. Subsequent metathesis with lithium bis(trifluoromethanesulfonyl)amide (LiTf2N) allows for a much desired, easy access to halide-free, bis(trifluoromethanesulfonyl)amide ionic liquids. Differential scanning calorimetry confirms that all investigated compounds qualify as ionic liquids (ILs). Moreover, it reveals for 1-methyl-4-n-dodecyl-1,2,4-triazolium methanesulfonate a rather complex thermal behavior involving formation of mesophases. Indeed, polarizing optical microscopy shows oily streaky textures that are characteristic for smectic liquid crystalline phases. Single-crystal X-ray diffraction structure analysis confirms formation of a layered structure. All compounds are photoluminescent. The color of fluorescence at room temperature can be tuned from blue to orange through the length of the alkyl side chain of the cation, the aromatic interactions between the cations, and the anion nature. In addition, at low temperatures (77 K) a close to white phosphorescence with average lifetimes in the millisecond time range can be observed for 1-methyl-4-n-butyl-triazolium methanesulfonate and all of the studied bis(trifluoromethanesulfonyl)amide ILs. All ILs show an appreciable liquidus range and thermal (up to 260-350 degrees C) and electrochemical stability. The presented set of ILs overcomes the sometimes problematic acidity and low stability of imidazolium ILs in basic environment and can be obtained easily in high purity without halide contamination. Overcoming two shortcomings of classical imidazolium ILs, they may be good alternatives for a number of applications and even enabling new ones.

  • 11. Di Marcantonio, M.
    et al.
    Namanga, J. E.
    Smetana, Volodymyr
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Gerlitzki, N.
    Vollkommer, F.
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Bacher, G.
    Nannen, E.
    Green-yellow emitting hybrid light emitting electrochemical cell2017Inngår i: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 5, nr 46, s. 12062-12068Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Light-emitting electrochemical cells (LECs) are attractive candidates for future low-cost lighting applications such as light-emitting smart tags, thanks to their simplicity, fully solution-based fabrication and flexibility. However, high brightness and efficiency in combination with satisfactory operation lifetimes need to be achieved for different emission colours bearing future device commercialization in mind. LECs emitting in the yellow-green spectral range, where the human eye is most sensitive are thereby particularly attractive. Here we present an improved hybrid LEC based on an Ir-iTMC, [Ir(4-Fppy)(2)(pbpy)][PF6] (4-Fppy = 2-(4-fluorophenyl) pyridinato, pbpy = 6-phenyl-2,2'-bipyridine) emitting at 557 nm. It features a luminance of 2400 cd m(-2) when driven at a constant voltage of 4 V, and a lifetime of 271 h at a luminance of 1500 cd m(-2) under pulsed current operation. The hybrid LEC shows an enhanced performance compared to a LEC solely based on the Ir-ITMC where operation lifetimes of 165 h at a luminance above 1200 cd m(-2) under pulsed current operation conditions were observed. The performance improvement was achieved by addition of a solution-processed ZnO nanoparticle film on top.

  • 12. Kelley, Steven P.
    et al.
    Pei, Hanwen
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Smetana, Volodymyr
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Rogers, Robin D.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). The University of Alabama, United States.
    Structural Consequences of Halogen Bonding in Dialkylimidazolium: A New Design Strategy for Ionic Liquids Illustrated with the I-2 Cocrystal and Acetonitrile Solvate of 1,3-Dimethylimidazolium Iodide2020Inngår i: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 20, nr 1, s. 498-505Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The reaction of 1,3-dimethylimidazolium-2-carboxylate with elemental iodine in acetonitrile rapidly affords crystalline iodide salts of the 1,3-dimethy1-2-iodoimidazolium cation ([C(1)mim-2-I](+)), [C(1)mim-2-I]I.0.5I(2), and [C(1)mim-2-1]I-0.5CH(3)CN, depending on the temperature. Analysis of the two structures shows the significant role of halogen bonding interactions between the cation and anion in the [C(1)mim-2-I]I salts, which reduces the ionicity of the compounds. This observation is backed by theoretical calculations revealing the importance of halogen bonding as a design strategy for ionic liquids (ILs), which, so far, has been underestimated. The halogen bonding is also analyzed in terms of this new design concept for ILs.

  • 13. Li, Min
    et al.
    Smetana, Volodymyr
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Iowa State University, USA.
    Wilk-Kozubek, Magdalena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Iowa State University, USA; Wrocław Research Centre EIT+, Poland.
    Mudryk, Yaroslav
    Alammar, Tarek
    Pecharsky, Vitalij K.
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Iowa State University, USA.
    Open-Framework Manganese(II) and Cobalt(II) Borophosphates with Helical Chains: Structures, Magnetic, and Luminescent Properties2017Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 56, nr 18, s. 11104-11112Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two borophosphates, (NH4)(1-2x)M1+x(H2O)(2)(BP2O8)center dot yH(2)O with M = Mn (I) and Co (II), synthesized hydrothermally crystallize in enantiomorphous space groups P6(5)22 and P6(1)22 with a = 9.6559(3) and 9.501(3) angstrom, c = 15.7939(6) and 15.582(4) angstrom, and V = 1275.3(1) and 1218.2(8) angstrom(3) for I and II, respectively. Both compounds feature helical chains composed of vertex-sharing tetrahedral PO4 and BO4 groups that are connected through O atoms to transition-metal cations, Mn2+ and Co2+, respectively. For the two crystallographically distinct-transition-metal cation sites present in the structure, this results in octahedral coordination with different degrees of distortion from the ideal symmetry. The crystal-field parameters, calculated from the corresponding absorption spectra, indicate that Mn2+ and Co2+ ions are located in a weak octahedral-like crystal field and suggest that the Co-ligand interactions are more covalent than the Mn-ligand ones. Luminescence measurements at room temperature reveal an orange emission that red-shifts upon lowering of the temperature to 77 K for I, while II is not luminescent. The luminescence lifetimes of I are 33.4 mu s at room temperature and 1.87 ms at 77 K. Both compounds are Curie-Weiss paramagnets with negative Weiss constants and effective magnetic moments expected for noninteracting Mn2+ and Co2+ cations but no clear long-range magnetic order above 2 K.

  • 14. Liu, J.
    et al.
    Mudryk, Y.
    Smetana, Volodymyr
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Iowa State University, USA.
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Iowa State University, USA.
    Pecharsky, V. K.
    Anomalous effects of Sc substitution and processing on magnetism and structure of (Gd1-xScx)(5)Ge-42019Inngår i: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 474, s. 482-492Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The kinetic arrest observed in the parent Gd5Ge4 gradually vanishes when a small fraction (x = 0.025, 0.05 and 0.10) of Gd is replaced by Sc in (Gd1-xScx)(5)Ge-4, and the magnetic ground state changes from antiferromagnetic (AFM) to ferromagnetic (FM). A first order phase transition coupled with the FM-AFM transition occurs at T-C = 41 K for x = 0.05 and at T-C = 53 K for x = 0.10 during heating in applied magnetic field of 1 kOe, and the thermal hysteresis is near 10 K. The first-order magnetic transition is coupled with the structural Sm5Ge4-type to Gd5Si4-type transformation. The magnetization measured as a function of applied magnetic field shows sharp metamagnetic-like behavior. At the same time, the AFM to paramagnetic transition in (Gd1-xScx)(5)Ge-4 with x = 0.10, is uncharacteristically broad indicating development of strong short-range AFM correlations above the Ned temperature. Comparison of the magnetization data of bulk, powdered, and metal-varnish composite samples of (Gd0.95Sc0.05)(5)Ge-4 shows that mechanical grinding and fabrication of a composite have little effect on the temperature of the first-order transformation, but short-range ordering and AFM/FM ratio below T-C are surprisingly strongly affected.

  • 15. Namanga, Jude E.
    et al.
    Gerlitzki, Niels
    Smetana, Volodymyr
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). U.S. Department of Energy, United States.
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Ruhr-Universität Bochum, Germany; U.S. Department of Energy, United States.
    Supramolecularly Caged Green-Emitting Ionic Ir(III)-Based Complex with Fluorinated CN Ligands and Its Application in Light-Emitting Electrochemical Cells2018Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, nr 13, s. 11026-11036Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ionic Ir(III) complexes are the most promising emitters in light emitting electrochemical cells (LECs), especially in the high energy emission range for which it is difficult to find emitters with sufficient efficiencies and lifetimes. To overcome this challenge, we introduced the concept of intramolecular pi-pi stacking of an ancillary ligand (6-phenyl-2,2'-bipyridine, pbpy) in the design of a new green-emitting iridium ionic transition metal complex with a fluoro-substituted cyclometallated ligand, 2-(4-fluorophenyOpyridinato (4Fppy). [Ir(4Fppy)(2)(pbpy)][PF6] has been synthesized and characterized and its photophysical and electrochemical properties have been studied. The complex emits green light with maxima at 561 and 556 nm under UV excitation from powder and thin film, respectively, and displays a high photoluminescence quantum yield (PLQY) of 78.5%. [Ir(4Fppy)(2)(pbpy)][PF6] based LECs driven under pulsed current conditions showed under an average current density of 100 A m(-2) (at 50% duty cycle) a maximum luminance of 1443 cd m(-2), resulting in 14.4 cd A(-1) and 7.4 lm W-1 current and power efficiencies, respectively. A remarkable long device lifetime of 214 h was observed. Reducing the average current density to 18.5 A m(-2) (at 75% duty cycle) led to an exceptional device performance of 19.3 cd A(-1) and 14.4 lm W1- for current and power efficiencies, an initial maximum luminance of 352 cd m(-2) and a lifetime of 617 h.

  • 16. Prodius, Denis
    et al.
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Ames Laboratory, US Department of Energy and Critical Materials Institute, USA.
    Rare earth metal-containing ionic liquids2018Inngår i: Coordination chemistry reviews, ISSN 0010-8545, E-ISSN 1873-3840, Vol. 363, s. 1-16Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    As an innovative tool, ionic liquids (ILs) are widely employed as an alternative, smart, reaction media (vs. traditional solvents) offering interesting technology solutions for dissolving, processing and recycling of metal-containing materials. The costly mining and refining of rare earths (RE), combined with increasing demand for high-tech and energy-related applications around the world, urgently requires effective approaches to improve the efficiency of rare earth separation and recovery. In this context, ionic liquids appear as an attractive technology solution. This review addresses the structural and coordination chemistry of ionic liquids comprising rare earth metals with the aim to add to understanding prospects of ionic liquids in the chemistry of rare earths.

  • 17. Prodius, Denis
    et al.
    Wilk-Kozubek, Magdalena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). US Department of Energy and Critical Materials Institute, USA; Iowa State University, USA; Wrocław Research Centre EIT+, Poland.
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). US Department of Energy and Critical Materials Institute, USA; Iowa State University, USA.
    Synthesis, structural characterization and luminescence properties of 1-carboxymethyl-3-ethylimidazolium chloride2018Inngår i: Acta crystallographica. Section C, Structural chemistry, ISSN 2053-2296, Vol. 74, s. 653-658Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A microcrystalline carboxyl-functionalized imidazolium chloride, namely 1-carboxymethyl-3-ethylimidazolium chloride, C7H11N2O2+center dot Cl-, has been synthesized and characterized by elemental analysis, attenuated total reflectance Fourier transform IR spectroscopy (ATR-FT-IR), single-crystal X-ray diffraction, thermal analysis (TGA/DSC), and photoluminescence spectroscopy. In the crystal structure, cations and anions are linked by C-H center dot center dot center dot Cl and C-H center dot center dot center dot O hydrogen bonds to create a helix along the [010] direction. Adjacent helical chains are further interconnected through O-H center dot center dot center dot Cl and C-H center dot center dot center dot O hydrogen bonds to form a (10(1) over bar) layer. Finally, neighboring layers are joined together via C-H center dot center dot center dot Cl contacts to generate a three-dimensional supramolecular architecture. Thermal analyses reveal that the compound melts at 449.7 K and is stable up to 560.0 K under a dynamic air atmosphere. Photoluminescence measurements show that the compound exhibits a blue fluorescence and a green phosphorescence associated with spin-allowed ((1)pi <- (1)pi*) and spin-forbidden ((1)pi <- (3)pi*) transitions, respectively. The average luminescence lifetime was determined to be 1.40 ns for the short-lived ((1)pi <- (1)pi*) transition and 105 ms for the long-lived ((1)pi <- (3)pi*) transition.

  • 18. Provino, Alessia
    et al.
    Smetana, Volodymyr
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Hackett, Timothy A.
    Paudyal, Durga
    Kashyap, Manish K.
    Bernini, Cristina
    Bhattacharyya, Amitava
    Dhar, Sudesh K.
    Pani, Marcella
    Gatti, Flavio
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Manfrinetti, Pietro
    Stability, Crystal Chemistry, and Magnetism of U2+xN21-xB6 and Nb3-yNi20+yB6 and the Role of Uranium in the Formation of the Quaternary U2-zNbzNi21B6 and U delta Nb3-delta Ni20B6 Systems2019Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 58, nr 22, s. 15045-15059Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We investigated the U-Ni-B and Nb-Ni-B systems to search for possible new heavy fermion compounds and superconducting materials. The formation, crystal chemistry, and physical properties of U2Ni21B6 and Nb3-yNi20+yB6 [ternary derivatives of the cubic Cr23C6-type (cF116, Fm3m)] have been studied; the formation of the hypothetical U3Ni20B6 and Nb2Ni21B6 has been disproved. U2Ni21B6 [a = 10.6701(2) angstrom] crystallizes in the ordered W2Cr21C6-type, whereas Nb3-yNi20+yB6 [a = 10.5842(1) angstrom] adopts the Mg3Ni20B6-type. Ni in U2Ni21B6 can be substituted by U, leading to the solid solution U2-xNi21+yB6 (0 <= x <= 0.3); oppositely, Nb in Nb3Ni20B6 is partially replaced by Ni, forming the solution Nb3-yNi20+yB6 (0 <= y <= 0.5), none of them reaching the limit corresponding to the hypothetically ordered U3Ni20B6 and Nb2Ni21B6. These results prompted us to investigate quaternary compounds U2-zNbzNi21B6 and U6Nb3-delta Ni20B6: strong competition in the occupancy of the 4a and 8c sites by U, Nb, and Ni atoms has been observed, with the 4a site occupied by U/Ni atoms only and the 8c site filled by U/Nb atoms only. U2Ni21B6, U2.3Ni20.7B6, and Nb3Ni20B6 are Pauli paramagnets. Interestingly, Nb2.5Ni20.5B6 shows ferromagnetism with T-c approximate to 11 K; the Curie-Weiss fit gives an effective magnetic moment of 2.78 mu(B)/Ni, suggesting that all Ni atoms in the formula unit contribute to the total magnetic moment. The M(H) data at 2 K further corroborate the ferromagnetic behavior with a saturation moment of 10 mu(B)/fu (approximate to 0.49 mu(B)/Ni). The magnetic moment of Ni at the 4a site induces a moment in all of the Ni atoms of the whole unit cell (32f and 48h sites), with all atoms ordering ferromagnetically at 11 K. Density functional theory (DFT) shows that the formation of U2Ni21B6 and Nb3Ni20B6 is energetically preferred. The various electronic states generating ferromagnetism on Nb2.5Ni20.5B6 and Pauli paramagnetism on U2Ni21B6 and Nb3Ni20B6 have been identified.

  • 19. Rhodehouse, Melissa L.
    et al.
    Bell, Thomas
    Smetana, Volodymyr
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). USDOE, United States.
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). USDOE, United States; Iowa State University, United States.
    Meyer, Gerd H.
    An Obscured or Nonexistent Binary Intermetallic, Co7Pr17, Its Existent Neighbor Co2Pr5, and Two New Ternaries in the System Co/Sn/Pr, CoSn3Pr1-x, and Co2-xSn7Pr32018Inngår i: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 18, nr 10, s. 6273-6283Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Four compounds are reported in this study. Co7Pr17 (10, cP96, P2(1)3, a = 13.4147(8) angstrom, Z = 4), either nonexistent or obscured in the Co/Pr phase diagram, has been obtained from a PrBr3 flux. With 29.2 mol % Co, it is close to Co2Pr5 (28.6 mol % Co, 2, C2Mn5 type of structure, mC28, C2/c, a = 16.5471(7) angstrom, b = 6.5107(3) angstrom, c = 7.1067(3) angstrom, beta = 96.230(3)degrees, Z = 4), existent in the Co/Pr phase diagram, produced by arc-melting of a stoichiometric mixture of the metals. The addition of the reactive metal tin to Co/Pr mixtures yielded two new ternary polar intermetallics, CoSn3Pr1-x (x = 0.04, 11, RuSn3La type, cP40, Pm(3) over barn, a = 9.587(3) angstrom, Z = 8) and Co2-xSn7Pr3 (x = 0.78, 12, Ni2-xSn7-yCe3 type, oC24, Cmmm, a = 4.5043(4) angstrom, b = 27.227(2) angstrom, c = 4.5444(3) angstrom, Z = 2). Electronic structure calculations reveal extensive heteroatomic Co-Pr interactions in the binaries with little homoatomic contributions. With tin as the third component in the ternaries, heteroatomic Co-Sn and Sn-Pr bonding interactions are dominant, following the sequence of coordination spheres around Co.

  • 20. Rhodehouse, Melissa L.
    et al.
    Bell, Thomas
    Smetana, Volodyrnyr
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Iowa State University, United States.
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Iowa State University, United States.
    Meyer, Gerd H.
    From the Nonexistent Polar Intermetallic Pt3Pr4 via Pt2-xPr3 to Pt/Sn/Pr Ternaries2018Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 57, nr 16, s. 9949-9961Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Although the Pt-Pr phase diagram has been explored well, recent work on rare-earth metal cluster halides with endohedral transition metal atoms has provided a new binary intermetallic that is nonexistent in the known phase diagram: The binary Pt3Pr4 (1) crystallizes in a new structure type (mP56, P21/c, a = 12.353(2) angstrom, b = 7.4837(9) angstrom, c = 17.279(2) angstrom, beta = 118.003(7)degrees, z = 8) With six crystallographically independent Pt as well as eight Pr positions. The subsequent detailed investigation has led to another previously unreported, binary phase with the Ga2Gd3 structure type, Pt2-xPr3 (2, tI80, I4/mcm, a = 11.931(9) A, c = 14.45(1) angstrom, z = 16), that is practically overlapping with the rhombohedral Pt2Pr3 existing in the phase diagram. Application of different tin containing fluxes to reproduce the newly detected phases brought about two almost iso-compositional temary compounds with Sn, Pt4Sn6Pr2.91 (3), and Pt4.Sn6Pr3 (4), as well as Pt12Sn24Pr4.84 (5). 3 is a representative of the Pt4Ge6Ce3 type (oP52, Pnma, a = 7.2863(3) A, b = 4.4909(2) angstrom, c = 35.114(2) angstrom), while 4 represents a new variant of the prolific T4E6R3 family (T = transition metal, E = main group (semOrnetal, R = rare-earth metal; Pt4Sn6Pr3: oP52, Pnma, a = 27.623(1) angstrom, b = 4.5958(2) A, c = 9.3499(5) A). Pt(12)sn(24)Prs_x (5) crystallizes as a variant of the Ni8Sn16Gd3 type (cI82, /m(-3), a = 12.274(1) A, z = 2). Electronic structure calculations provide hints on the origin of the structural changes (pseudo-polymorphism) for PtxPr3 with x = 1.97 and 2.00, respectively, and reveal that heteroatomic Pt-Pr bonding strongly dominates in both binaries while the addition of the reactive metal tin leads to dominating Pt-Sn bonding interactions in the ternaries; Pt Pt bonding interactions are strong but represent a minority in the binaries and are not present at all in the ternaries.

  • 21. Sangeetha, N. S.
    et al.
    Anand, V. K.
    Cuervo-Reyes, Eduardo
    Smetana, Volodymyr
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Johnston, D. C.
    Enhanced moments of Eu in single crystals of the metallic helical antiferromagnet EuCo2-yAs22018Inngår i: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 97, nr 14Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The compound EuCo2-yAs2 with the tetragonal ThCr2Si2 structure is known to contain Eu+2 ions with spin S = 7/2 that order below a temperature T-N approximate to 47 K into an antiferromagnetic (AFM) proper helical structure with the ordered moments aligned in the tetragonal ab plane, perpendicular to the helix axis along the c axis, with no contribution from the Co atoms. Here we carry out a detailed investigation of the properties of single crystals. We consistently find about 5% vacancies on the Co site from energy-dispersive x-ray analysis and x-ray diffraction refinements. Enhanced ordered and effective moments of the Eu spins are found in most of our crystals. Electronic structure calculations indicate that the enhanced moments arise from polarization of the d bands, as occurs in ferromagnetic Gd metal. Electrical resistivity measurements indicate metallic behavior. The low-field in-plane magnetic susceptibilities x(ab) (T < T-N) for several crystals are reported that are fitted well by unified molecular field theory (MFT), and the Eu-Eu exchange interactions J(ij) are extracted from the fits. High-field magnetization M data for magnetic fields H parallel to ab reveal what appears to be a first-order spin-flop transition followed at higher field by a second-order metamagnetic transition of unknown origin, and then by another second-order transition to the paramagnetic (PM) state. For H parallel to c, the magnetization shows only a second-order transition from the canted AFM to the PM state, as expected. The critical fields for the AFM to PM transition are in approximate agreement with the predictions of MFT. Heat capacity C-p measurements in zero and high H are reported. Phase diagrams for H parallel to c and H parallel to ab versus T are constructed from the high-field M(H, T) and C-p(H, T) measurements. The magnetic part C-mag(T, H = 0) of C-p(T, H = 0) is extracted and is fitted rather well below T-N by MFT, although dynamic short-range AFM order is apparent in Cmag(T) up to about 70 K, where the molar entropy attains its high-T limit of R ln 8.

  • 22. Sangeetha, N. S.
    et al.
    Smetana, Volodymyr
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Johnston, D. C.
    Antiferromagnetism in semiconducting SrMn2Sb2 and BaMn2Sb2 single crystals2018Inngår i: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 97, nr 1, artikkel-id 014402Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Crystals of SrMn2Sb2 and BaMn2Sb2 were grown using Sn flux and characterized by powder and single-crystal x-ray diffraction, respectively, and by single-crystal electrical resistivity rho, heat capacity C-p, and magnetic susceptibility chi measurements versus temperature T, and magnetization versus field M(H) isotherm measurements. SrMn2Sb2 adopts the trigonal CaAl2Si2-type structure whereas BaMn2Sb2 crystallizes in the tetragonal ThCr2Si2-type structure. The rho(T) data indicate semiconducting behaviors for both compounds with activation energies of greater than or similar to 0.35 eV for SrMn2Sb2 and 0.16 eV for BaMn2Sb2. The chi(T) and C-p(T) data reveal antiferromagnetic (AFM) ordering at T-N = 110 K for SrMn2Sb2 and 450 K for BaMn2Sb2. The anisotropic chi(T <= T-N) data also show that the ordered moments in SrMn2Sb2 are aligned in the hexagonal ab plane whereas the ordered moments in BaMn2Sb2 are aligned collinearly along the tetragonal c axis. The ab-plane M(H) data for SrMn2Sb2 exhibit a continuous metamagnetic transition at low fields 0 < H less than or similar to 1 T, whereas BaMn2Sb2 exhibits no metamagnetic transitions up to 5.5 T. The chi(T) and C-p(T) data for SrMn2Sb2 and BaMn2Sb2 indicate strong dynamic short-range AFM correlations above their respective TN up to at least 900 K within a local-moment picture, corresponding to quasi-two-dimensional magnetic behavior. The present results and a survey of the literature for Mn pnictides with the CaAl2Si2 and ThCr2Si2 crystal structures show that the T-N values for the CaAl2Si2-type compounds are much smaller than those for the ThCr2Si2-type materials.

  • 23. Sangeetha, N. S.
    et al.
    Smetana, Volodymyr
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Johnston, D. C.
    Helical antiferromagnetic ordering in EuNi1.95As2 single crystals2019Inngår i: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 100, nr 9, artikkel-id 094438Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Eu(+2 )spins-7/2 in EuNi2As2 with the body-centered tetragonal ThCr2Si2 structure order antiferromagnetically below the Ned temperature T-N = 15 K into a helical antiferromagnetic (AFM) structure with the helix axis aligned along the tetragonal c axis and the Eu ordered moments aligned ferromagnetically within the ab plane as previously reported from neutron diffraction measurements [T. Jin et al., Phys. Rev. B 99, 014425 (2019)]. Here we study the crystallographic, magnetic, thermal, and electronic transport properties of Bi flux grown single crystals using single-crystal x-ray diffraction, anisotropic magnetic susceptibility chi, isothermal magnetization M, heat capacity C-p, and electrical resistivity rho measurements versus applied magnetic field H and temperature T. Vacancies are found on the Ni sites corresponding to the composition EuNi1.95(1)As2. A good fit of the rho(T) data by the Bloch-Grijneisen theory for metals was obtained. The chi(ab )(T) data below T-N are fitted well by molecular field theory (MFT), and the helix turn angle kd and the Eu-Eu Heisenberg exchange constants are extracted from the fit parameters. The kd value is in good agreement with the neutron-diffraction result. The magnetic contribution to the zero-field heat capacity below T-N is also fitted by MFT. The isothermal in-plane magnetization M-ab exhibits two metamagnetic transitions versus H, whereas M-c(T = 2 K) is nearly linear up to H = 14 T, both behaviors being consistent with MFT. The M-c(H, T), rho(H-c, T ), and C-p(H-c, T ) data yielded aH(c)-T phase diagram separating the AFM and paramagnetic phases in good agreement with MFT. Anisotropic chi(T) literature data for the ThCr2Si2-type helical antiferromagnet EuRh2As2 were also fitted well by MFT. A comparison is made between the crystallographic and magnetic properties of ThCr2Si2-type EuM(2)Pn(2) compounds with M = Fe, Co, Ni, Cu, or Rh, and Pn = P or As, where only ferromagnetic and c-axis helical AFM structures are found.

  • 24. Sangeetha, N. S.
    et al.
    Wang, L-L
    Smirnov, A.
    Smetana, Volodymyr
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Johnson, D. D.
    Tanatar, M. A.
    Prozorov, R.
    Johnston, D. C.
    Non-Fermi-liquid types of behavior associated with a magnetic quantum critical point in Sr(Co1-xNix)(2)As-2 single crystals2019Inngår i: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 100, nr 9, artikkel-id 094447Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The compound SrCo2As2 with the body-centered tetragonal ThCr2Si2 structure is known to remain paramagnetic down to a temperature T = 0.05 K, but inelastic neutron scattering studies have shown that both ferromagnetic (FM) and antiferromagnetic (AFM) fluctuations occur in single crystals. Thus it is of interest to study how the magnetism evolves on doping SrCo2As2. Previous work on polycrystalline samples of Sr(Co1-xNix)(2)As-2 indicated the development of AFM order for 0 < x less than or similar to 0.3. Here we studied single crystals of Sr(Co1-xNix)(2)As-2 for 0 < x <= 1 and confirmed the occurrence of AFM order which we deduce to have a c-axis helix structure. We also find evidence for an unusual composition-induced magnetic quantum critical point at x approximate to 0.3 where non-Fermi-liquid types of behavior were revealed by heat capacity and electrical resisitivity measurements at low T. Electron-doped Sr (Co1-xNix)(2)As-2 single crystals with compositions x = 0 to 0.9 were grown out of self-flux and SrNi2As2 single crystals out of Bi flux. The crystals were characterized using single-crystal x-ray diffraction (XRD) at room temperature, and magnetic susceptibility chi (H, T), isothermal magnetization M(H, T), heat capacity C-p (H, T), and electrical resistivity rho(H, T) measurements versus applied magnetic field H and T. The XRD studies show that the system undergoes a continuous structural crossover from the uncollapsed-tetragonal (ucT) structure to the collapsed tetragonal (cT) structure with increasing Ni doping. The chi (T) data show that SrCo2As2 exhibits an AFM ground state almost immediately upon Ni doping on the Co site. Ab initio electronic-structure calculations for x = 0 and 0.15 indicate that a flat band with a peak in the density of states just above the Fermi energy is responsible for this initial magnetic-ordering behavior on Ni doping. The AFM ordering is observed in the range 0.013 <= x <= 0.25 with the ordered moments aligned in the ab plane and with a maximum ordering temperature T-N = 26.5 K at x = 0.10. The Curie-Weiss-like T dependence of chi in the paramagnetic (PM) state indicates dominant FM interactions. The behavior of the anisotropic susceptibilities below T-N suggests a planar helical magnetic ground state with a composition-dependent pitch based on a local-moment molecular-field-theory model, with FM interactions in the ab plane and weaker AFM interactions along the helix c axis. However, the small ordered (saturation) moments similar to 0.1 mu(B) per transition metal atom, where mu(B) is the Bohr magneton, and the values of the Rhodes-Wohlfarth ratio indicate that the magnetism is itinerant. The high-field M(H) isotherms and the low-field chi(-1) (T > T-N) data were successfully analyzed within the framework of Takahashi's theory of FM spin fluctuations. The C-p (T) at low T exhibits Fermi-liquid behavior for 0 <= x <= 0.15, whereas an evolution to a logarithmic non-Fermi-liquid (NFL) behavior is found for x = 0.2 to 0.3. The logarithmic dependence is suppressed in an applied magnetic field. The low-T rho(H = 0, T) data show a T-2 dependence for 0 <= x <= 0.20 and a power-law dependence rho(H = 0, T) = rho(0) + AT(n) with n < 2 for x = 0.20 and 0.30. The exponent n shows a notable field dependence, suggesting both doping- and magnetic-field-tuned quantum critical phenomena. These low-T NFL types of behavior observed in the C-p and rho measurements are most evident near the quantum critical concentration x approximate to 0.3 at which a T = 0 composition-induced transition from the AFM phase to the PM phase occurs.

  • 25.
    Smetana, Volodymyr
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Mudryk, Yaroslav
    Pecharsky, Vitalij K.
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Controlling magnetism via transition metal exchange in the series of intermetallics Eu(T1, T2)(5)In (T = Cu, Ag, Au)2018Inngår i: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 6, nr 6, s. 1353-1362Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Three series of intermetallic compounds Eu(T1, T2)(5)In (T = Cu, Ag, Au) have been investigated over their full compositional ranges. Single crystals of all compounds have been obtained by self-flux and were analyzed by single crystal X-ray diffraction revealing that the representatives fall into two structure types: CeCu6 (oP28, Pnma, a = 8.832(3)-9.121(2) angstrom, b = 5.306(2)-5.645(1) angstrom, c = 11.059(4)-11.437(3) angstrom, V = 518.3(3)-588.9(2) angstrom(3)) and YbMo2Al4 (t/14, /4/mmm, a = 7.139(2)-7.199(2) angstrom, c = 5.417(3)-5.508(1) angstrom, V = 276.1(2)-285.8(1) angstrom(3)). The structural preference was found to depend on the cation/anion size ratio, while the positional preference within the CeCu6 type structure shows an apparent correlation with the anion size. Chemical compression, hence, a change in cell volume, which occurs upon anion substitution, appears to be the main driving force for the change of magnetic ordering. While EuAg5In shows antiferromagnetic behavior at low temperatures, mixing Cu and Au within the same type of structure results in considerable changes in the magnetism. The Eu(Cu, Au)(5)In alloys with CeCu6 structure show complex magnetic behaviors and a strong magnetic field-induced spin-reorientation transition with the critical field of the transition being dependent on Cu/Au ratio. The alloys adopting the YbMo2Al4 type structure are ferromagnets exhibiting unusually high magnetic moments. The heat capacity of EuAu2.66Cu2.34In reveals a double-peak structure evolving with the magnetic field. However, low-temperature X-ray powder diffraction does not show a structural transition.

  • 26.
    Smetana, Volodymyr
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Iowa State University, United States.
    Rhodehouse, Melissa
    Meyer, Gerd
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Iowa State University, United States.
    Gold Polar Intermetallics: Structural Versatility through Exclusive Bonding Motifs2017Inngår i: Accounts of Chemical Research, ISSN 0001-4842, E-ISSN 1520-4898, Vol. 50, nr 11, s. 2633-2641Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    The design of new materials with desired chemical and physical characteristics requires thorough understanding of the underlying composition structure property relationships and the experimental possibility of their modification through the controlled involvement of new components. From this point of view, intermetallic phases, a class of compounds formed by two or more metals, present an endless field of combinations that produce several chemical compound classes ranging from simple alloys to true ionic compounds. Polar intermetallics (PICs) belong to the class that is electronically situated in the middle, between Hume-Rothery phases and Zintl compounds and possessing e/a (valence electron per atom) values around 2. In contrast to the latter, where logical rules of formation and classification systems were developed decades ago, polar intermetallics remain a dark horse with a huge diversity of crystal structures but unclear mechanisms of their formation. Partial incorporation of structural and bonding features from both nonpolar and Zintl compounds is commonly observed here. A decent number of PICs can be described in terms of complex metallic alloys (CMAs) following the Hume-Rothery electron-counting schemes but exhibit electronic structure changes that cannot be explained by the latter. Our research is aimed at the discovery and synthesis of new polar intermetallic compounds, their structural characterization, and investigation of their properties in line with the analysis of the principles connecting all of these components. Understanding of the basic structural tendencies is one of the most anticipated outcomes of this analysis, and systematization of the available knowledge is the initial and most important step.

    In this Account, we focus on a well-represented but rather small section of PICs: ternary intermetallic compounds of gold with electropositive and post-transition metals of groups 12 to 15. The strong influence of relativistic effects in its chemical bonding results in special, frequently unique structural motifs, while at the same time gold participates in common structure types as an ordinary transition element. Enhanced bonding strength leads to the formation and stabilization of complex homo-and heteroatomic clusters and networks that are compositionally restricted to just a few options throughout the periodic table. Because it has the highest absolute electronegativity among metals, comparable to those of some halogens, gold usually plays the role of an anion, even being able to form true salts with the most electropositive metals. We discuss the occurrence of the structure types and show the place of gold intermetallics in the general picture. Among the structures considered are ones as common as AIB(2) or BaAl4 types, in line with the recently discovered diamond-like homoatomic metal networks, formation of local fivefold symmetry, different types of tunneled structures, and more complex intergrown multicomponent structures.

  • 27.
    Smetana, Volodymyr
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Wilk-Kozubek, Magdalena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). PORT Polish Center for Technology Development, Poland.
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Active-Transition-Metal Tellurides: Through Crystal Structures to Physical Properties2019Inngår i: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 19, nr 9, s. 5429-5440Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Materials showing thermoelectric properties known as thermoelectrics can reversibly convert a temperature gradient into electricity. Since the vast majority of energy we use comes from thermal processes or creates thermal energy as waste energy, the search for materials able to efficiently convert thermal energy is of extreme importance. The discovery of a new, highly efficient thermoelectric material is complicated due to the special requirements imposed on the combination of electrical and thermal transport properties. Metal chalcogenides (MCs) have attracted significant attention as high performance thermoelectric materials. Their subgroup, active-transition-metal chalcogenides, shows structural and compositional diversity, including a wide occurrence of low-dimensional structural motifs, which opens up a fruitful area for explorations. This area has been preliminarily explored from both structural and functional viewpoints revealing very promising directions and unique compounds. Nevertheless, systematic investigations on transport properties are still missing. Available data suggests the presence of low bandgap semiconductors satisfying at least one of the conditions for a good thermoelectric, whereas the potential for structural and electronic variation in the form of active metal doping and substitution leaves a decent chance to uncover a candidate with acceptably low thermal conductivity and subsequently high thermoelectric performance.

  • 28. Spielberg, Eike T.
    et al.
    Campbell, Paul S.
    Szeto, Kai C.
    Mallick, Bert
    Schaumann, Julian
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Ruhr-University Bochum, Germany.
    Sodium Salicylate: An In-Depth Thermal and Photophysical Study2018Inngår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 24, nr 58, s. 15638-15648Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sodium salicylate (2-hydroxybenzoate) has been fully characterised by single-crystal X-ray diffraction (SCXRD), thermogravimetric analysis in combination with in operando FTIR spectroscopy and GC-MS, as well as by UV/Vis absorption and photoluminescence spectroscopy backed up by DFT calculations. SCXRD revealed a layered crystal structure composed of ionic sheets formed by Na+-O contacts sandwiched between pi-stacked aromatic rings of the salicylate anion oriented perpendicular to the layer plane. Only weak van der Waals interactions hold the individual sheets together. No solid/solid or solid/liquid phase transitions were observed upon heating, but a three-step decomposition was observed, with the first onset at 245 degrees C corresponding to concomitant release of CO2 and phenol. The UV/Vis absorption spectra show temperature-dependent absorption bands at around 305 and/or 345nm, which according to DFT calculations correspond to the absorption of the carboxylate or phenolate proton transfer species, respectively. In solution, indications of the phenolate species are found only in a very apolar solvent (cyclohexane). Because of excited-state relaxation, emission always occurs from the phenolate structure, which explains the large Stokes shift.

  • 29. Tang, Si-Fu
    et al.
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Highly Luminescent Ionic Liquids Based on Complex Lanthanide Saccharinates2019Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 58, nr 17, s. 11569-11578Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Four strongly luminescent ionic liquids with complex lanthanide saccharinate anions, [C(4)mim](3)[Eu-Sac)(6)(H2O)(2)] (1), {C(4)mpy}(5){[Ln-(Sac)(6)(H2O)(2)][Ln-(Sac)(5)(H2O)(3)]}{(H2O)(2)(CH3CN)(2)} (Ln = Sm for 2a; Ln = Eu for 2b), and [C(4)mpy](3)[Eu(Sac)(6)][CH3CN] (3) (C(4)mim = 1-butyl-3-methylimidazolium; C(4)mpy = N-butyl-4-methylpyridinium; Sac = saccharinate), have been obtained by reacting the ionic liquids 1-butyl-3-methylimidazolium saccharinate, [C(4)mim] [Sac], and N-butyl-4-methylpyridinium saccharinate, [C(4)mpy] [Sac], with the respective lanthanide saccharinates. Single-crystal X-ray diffraction analyses reveal the respective lanthanide center to be six- or eight-coordinated by five or six saccharinate anions and two or three aqua ligands in the cases of 1 and 2 when lanthanide saccharinated hydrate was employed as the starting material. Coordination of water to the lanthanide can be avoided when using the anhydrous lanthanide saccharinate as shown by the structure of 3. Using a co-solvent, acetonitrile, to facilitate the reaction led to incorporation of solvent molecules into the crystal structure of the final materials (2 and 3). Differential scanning calorimetry analyses reveal that 1 is an ionic liquid whereas 2 and 3 are low-temperature molten salts. The three europium(III)-containing compounds (1, 2b, and 3) all show characteristic intense red emissions of Eu(III) upon excitation into levels of the saccharinate ligands (321 nm) or Eu(III) (393 nm). At room temperature, the decay times of 1 and 2b are all similar to 0.5 ms, whereas the decay time of 3 amounts to 3.85 ms due to removal of aqua ligands in the first coordination sphere; accordingly, the quantum efficiencies of 1, 2b, and 3 were determined to be 15.9%, 22.95%, and 57.75%, respectively. The CIE chromaticity coordinates for all Eu compounds are in the red region and approach the NTSC standard CIE values when the temperature is increased. Sm(III)-containing compound 2a shows characteristic Sm(III) emission peaks. As expected, the CIE coordinates of samarium compound 2a fall in the orangered region.

  • 30. Tessitore, Gabriella
    et al.
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Kramer, Karl W.
    Luminescence and energy transfer in beta-NaGdF4: Eu3+, Er3+ nanocrystalline samples from a room temperature synthesis2018Inngår i: New Journal of Chemistry, ISSN 1144-0546, E-ISSN 1369-9261, Vol. 42, nr 1, s. 237-245Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Phase pure hexagonal beta-NaGdF4: Eu3+, Er3+ samples of less than 10 nm in crystallite size were synthesized in anhydrous ethylene glycol within 24 hours at room temperature. The materials were characterized by powder X-ray diffraction, electron microscopy, and luminescence spectroscopy. After Gd3+ excitation at 273 nm Eu3+ luminescence from the D-5(J) states dominates over Gd3+ P-6(J) emission and only weak Er3+ emissions could be observed due to strong Gd -> Eu and weak Gd -> Er energy transfer. Excitation at 377 nm results in Er3+ H-2(9/2) and Eu3+ D-5(J) emissions. The concentration dependence of the Er3+ and Eu3+ luminescence intensities points to independent behavior of the dopant ions without Er -> Eu or Eu -> Er energy transfer. Eu3+ excitation at 394 nm results in Eu3+ D-5(J) emissions only and confirms the absence of Eu-Er energy transfer. Eu3+ luminescence from the D-5(J) states prevails for all investigated excitations. The optimum Eu3+ doping level is close to 5%. Significant Er3+ luminescence was observed for 377 nm excitation only. The strong H-2(9/2) and weak S-4(3/2) Er3+ emissions indicate small losses by multiphonon relaxation and a good quality of the nanomaterial. Er co-doping hinders the energy migration on the Gd3+ and Eu3+ sublattices which results in higher Gd3+/Eu3+ and Eu3+ D-5(1)/D-5(0) emission ratios.

  • 31. Tessitore, Gabriella
    et al.
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Krämer, Karl W.
    Upconversion luminescence in sub-10 nm b-NaGdF4: Yb3+,Er3+ nanoparticles2019Inngår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 9, nr 60, s. 34784-34792Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sub-10 nm beta-NaGdF4:18% Yb3+,2% Er3+ nanoparticles were synthesized in ethylene glycol and various ionic liquids under microwave heating. The products were characterized by powder X-ray diffraction, electron microscopy, and upconversion (UC) luminescence spectroscopy. After Yb3+ excitation at 970 nm, Er3+ ions are excited by energy transfer upconversion and show the typical green and red emission bands. The UC luminescence intensity was optimized with respect to reactant concentrations, solvents, and reaction temperature and time. The strongest UC emission was achieved for sub-20 nm core-shell nanoparticles which were obtained in the ionic liquid diallyldimethylammonium bis(trifluoromethanesulfonyl)amide from a two-step synthesis without intermediate separation. Strictly anhydrous reaction conditions, a high fluoride/rare earth ion ratio, and a core-shell structure are important parameters to obtain highly luminescent nanoparticles. These conditions reduce non-radiative losses due to defects and high energy acceptor modes of surface ligands. A low power excitation of the core-shell particles by 70 mW at 970 nm results in an impressive UC emission intensity of 0.12% compared to the bulk sample.

  • 32. Wang, Guangmei
    et al.
    Valldor, Martin
    Dorn, Katharina V.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Wilk-Kozubek, Magdalena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). PORT Polish Center for Technology Development, Poland.
    Smetana, Volodymyr
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Ruhr-Universität Bochum, Germany.
    Ionothermal Synthesis Enables Access to 3D Open Framework Manganese Phosphates Containing Extra-Large 18-Ring Channels2019Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 31, nr 18, s. 7329-7339Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An ionothermal synthesis study of transition metal phosphates using the ionic liquid 1-butyl-4-methylpyridinium hexafluorophosphate [C(4)mpy] [PF6] yielded four new, different open framework manganese compounds, that is, K2Mn3 (HPO4)(2)(PO3F)F-2 (1), (NH4)(2)Mn-3 (HPO4)(2) (PO3F)-F-2 (2), KMn3 (H2PO4)(HPO4)(2)F-2 (3), and (NH4)Mn-3(H2PO4)(PO3F)(2)F-2 (4). The obtained products not only feature new framework topologies unprecedented in the family of phosphates but also interesting properties as the transition metal gives rise to both luminescent (rendering them potential nonrare earth containing red emitting phosphors) and unconventional magnetic properties governed by geometric frustrations. Aside from the structural analysis (powder and single-crystal X-ray diffraction, infrared spectroscopy), a variety of characterization methods (photoluminescence spectroscopy and magnetic measurements) were applied to study the material's properties. Single crystal X-ray studies reveal that 1 (P2(1)/c with a = 5.501(1), b = 14.203(3), c = 16.905(4) angstrom, beta = 108.65(3)degrees, V = 1251.4 angstrom(3), and Z = 4) and 2 (P2(1)/c with a = 5.587(1), b = 14.507(3), c = 17.364(3) angstrom, beta = 108.75(3)degrees, V = 1332.6(5) angstrom(3), and Z = 4) feature S-shaped 18-ring channels along [100], which are formed by trimer-Mn3O9F2 chains parallel to [100] and interconnecting PO3 (OH) and PO3F tetrahedra. The structure of compounds 3 (C2/c with a = 20.307(4), b = 7.635(1), c = 7.834(2) angstrom, beta = 103.26(3)degrees, V = 1182.2(4) angstrom(3), and Z = 4) and 4 (C2/c with a = 20.402(4), b = 7.673(1), c = 7.845(2) angstrom, beta = 103.56(3)degrees, V = 1193.8(4) angstrom(3), and Z = 4) are characterized by layers, which are built of Mn3O8F4 octahedra trimers, with Kagome topology parallel to the be plane featuring 3,6-ring channels. The layers are stacked according to a sequence of AA(i) along the a axis. Taking into account the [P(2)O-3(OH)/P(2)O3F] tetrahedra, the Kagome layers are replenished to a Mn3O2 (HPO4)/Mn3O2 (PO3F) composition, which are interlinked by [P(1)O-2(OH)(2)] forming 10-ring channels parallel to [001]. Charge compensation of the macroanions is achieved by K+ (1 and 3) and (NH4)(+) (2 and 4) cations. At room temperature, compounds 1-4 demonstrate a reddish orange emission ascribed to the spin-forbidden T-4(1g)((4)G) -> (6)A(1g) (S-6) transition of the Mn2+ ions. Upon lowering the temperature to 77 K, the emission of each compound is red-shifted and becomes pure red. Compounds 1 and 2 contain spin trimers with a presumable doubled ground state. The intertrimer magnetic coupling is relatively weak, and small ferrimagnetic domains are possible in 1. The magnetic behavior of 3 and 4 can be considered as antiferromagnetic. This can be understood as their staircase Kagome lattices are distorted, meaning that the intrinsic geometrical frustration is lifted.

  • 33. Wang, Guangmei
    et al.
    Valldor, Martin
    Siebeneichler, Stefanie
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Wilk-Kozubek, Magdalena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Łukasiewicz Research Network-PORT Polish Center for Technology Development, Poland.
    Smetana, Volodymyr
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Mudring, Anja-Verena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Ruhr-Universität Bochum, Germany.
    Ionothernnal Synthesis, Structures, and Magnetism of Three New Open Framework Iron Halide-Phosphates2019Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 58, nr 19, s. 13203-13212Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A set of different open framework iron phosphates have been synthesized ionothermally using a task-specific ionic liquid, 1-butyl-4-methylpyridinium hexafluorophosphate, that acts in the synthesis as the reaction medium and mineralizer: (NH4)(2)Fe-2(HPO4)(PO4)Cl2F (1) and K2Fe2(HPO4(PO4)Cl2F (2) exhibit similar composition and closely related structural features. Both structures consist of {Fe-2(HPO4)(PO4)-Cl2F}(2)- macroanions and charge balancing ammonium or potassium cations. Their open framework structure contains layers and chains of corner-linked {Fe(1)O2Cl4} and {Fe(2)F2O4} octahedra, respectively, interconnected by PO4 tetrahedra forming 10-ring channels. KFe(PO3F)F-2 (3) is built up by {Fe[(PO3F)(4/3)F-2/2]}{Fe(PO3F)(2/3) F2/2F2} layers separated by K+ cations. Chains of alternating {FeF2O4} and {FeO2F4} octahedra, which are linear for 1 but undulated for 2, are linked to each other via corner-sharing {PO3F} tetrahedra with the fluorine pointing into the interlayer space. The compounds were characterized by means of single crystal and powder X-ray diffraction, infrared spectroscopy, and magnetic measurements. 1 reveals a strong ground state spin anisotropy with a spin 5/2 state and a magnetic moment of 5.3 mu(B) /Fe3+. Specific heat and magnetic data unveil three magnetic transitions at 95, 50, and 3.6 K. Compound 2 has a very similar crystal structure as compared to 1 but exhibits a different magnetic behavior: a slightly lower magnetic moment of 4.7 mu(B)/Fe3+ and a magnetic transition to a canted antiferromagnetic state below 90 K. Compound 3 exhibits typical paramagnetic behavior close to room-temperature (5.71 mu(B)/Fe3+). There are no clear indications for a phase transition down to 2 K despite strong antiferromagnetic spin-spin interactions; only a magnetic anomaly appears at 50 K in the zero-field cooled data.

1 - 33 of 33
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