Inga Schellenberg

Publications of Inga Schellenberg

• Doped semimetal clusters: ternary, intermetalloid anions [Ln@Sn7Bi7]4- and [Ln@Sn4Bi9]4- (Ln = La, Ce) with adjustable magnetic properties.

  Authors: Felicitas Lips, Małgorzata Hołyńska, Rodolphe Clérac, Uwe Linne, Inga Schellenberg, Rainer Pöttgen, Florian Weigend, Stefanie Dehnen

  Journal of the American Chemical Society. 11/2011; 134(2):1181-91.

  Two K([2.2.2]crypt) salts of lanthanide-doped semimetal clusters were prepared, both of which contain at the same time two types of ternary intermetalloid anions, [Ln@Sn(7)Bi(7)](4-) andTwo K([2.2.2]crypt) salts of lanthanide-doped semimetal clusters were prepared, both of which contain at the same time two types of ternary intermetalloid anions, [Ln@Sn(7)Bi(7)](4-) and [Ln@Sn(4)Bi(9)](4-), in 0.70:0.30 (Ln = La) or 0.39:0.61 (Ln = Ce) ratios. The cluster shells represent nondeltahedral, fullerane-type arrangements of 14 or 13 main group metal atoms that embed the Ln(3+) cations. The assignment of formal +III oxidation states for the Ln sites was confirmed by means of magnetic measurements that reveal a diamagnetic La(III) compound and a paramagnetic Ce(III) analogue. Whereas the cluster anions with a 14-atomic main-group metal cage represent the second examples in addition to a related Eu(II) cluster published just recently, the 13-atomic cages exhibit a yet unprecedented enneahedral topology. In contrast to the larger cages, which accord to the Zintl-Klemm-Busmann electron number-structure correlation, the smaller clusters require a more profound interpretation of the bonding situation. Quantum chemical investigations served to shed light on these unusual complexes and showed significant narrowing of the HOMO-LUMO gap upon incorporation of Ce(3+) within the semimetal cages.

• Surprising luminescent properties of the polyphosphates Ln(PO3)3:Eu (Ln = Y, Gd, Lu).

  Authors: Henning A Höppe, Karolina Kazmierczak, Sylwia Kacprzak, Inga Schellenberg, Rainer Pöttgen

  Dalton transactions (Cambridge, England : 2003). 06/2011; 40(39):9971-6.

  The optical emission properties of the lanthanoid catena-polyphosphates Ln(PO(3))(3) (Ln = Y, Gd, Lu) doped with europium were investigated. Incommensurately modulated β-Y(PO(3))(3):Eu (super spaceThe optical emission properties of the lanthanoid catena-polyphosphates Ln(PO(3))(3) (Ln = Y, Gd, Lu) doped with europium were investigated. Incommensurately modulated β-Y(PO(3))(3):Eu (super space group Cc (0|0.364|0)0) and Gd(PO(3))(3):Eu (space group I2/a) show the usual emission characteristics of Eu(3+), while in Lu(PO(3))(3):Eu (space group Cc) the europium is unprecedentedly partially reduced to the divalent state, as proven by both a broad emission band at 406 nm excited at 279 nm and an EPR spectroscopic investigation. (151)Eu-Mössbauer spectroscopy showed that only a very small part of the europium is reduced in Lu(PO(3))(3):Eu. An explanation for this unusual behaviour is given.

• Indium flux-growth of Eu2AuGe3: a new germanide with an AlB2 superstructure.

  Authors: C Peter Sebastian, Christos D Malliakas, Maria Chondroudi, Inga Schellenberg, Sudhindra Rayaprol, Rolf-Dieter Hoffmann, Rainer Pöttgen, Mercouri G Kanatzidis

  Inorganic chemistry. 10/2010; 49(20):9574-80.

  The germanide Eu(2)AuGe(3) was obtained as large single crystals in high yield from a reaction of the elements in liquid indium. At room temperature Eu(2)AuGe(3) crystallizes with the Ca(2)AgSi(3)The germanide Eu(2)AuGe(3) was obtained as large single crystals in high yield from a reaction of the elements in liquid indium. At room temperature Eu(2)AuGe(3) crystallizes with the Ca(2)AgSi(3) type, space group Fmmm, an ordered variant of the AlB(2) type: a = 857.7(4), b = 1485.5(10), c = 900.2(4) pm. The gold and germanium atoms build up slightly distorted graphite-like layers which consist of Ge(6) and Au(2)Ge(4) hexagons, leading to two different hexagonal-prismatic coordination environments for the europium atoms. Magnetic susceptibility data showed Curie-Weiss law behavior above 50 K and antiferromagnetic ordering at 11 K. The experimentally measured magnetic moment indicates divalent europium. The compound exhibits a distinct magnetic anisotropy based on single crystal measurements and at 5 K it shows a metamagnetic transition at ∼10 kOe. Electrical conductivity measurements show metallic behavior. The structural transition at 130 K observed in the single crystal data was very well supported by the conductivity measurements. (151)Eu Mössbauer spectroscopic data show an isomer shift of -11.24 mm/s at 77 K, supporting the divalent character of europium. In the magnetically ordered regime one observes superposition of two signals with hyperfine fields of 26.0 (89%) and 3.5 (11%) T, respectively, indicating differently ordered domains.

• Local moments and symmetry breaking in metallic PrMnSbO

  Authors: Simon A. J. Kimber, Adrian H. Hill, Yu-Zhong Zhang, Harald O. Jeschke, Roser Valentí, Clemens Ritter, Inga Schellenberg, Wilfred Hermes, Rainer Pöttgen, Dimitri N. Argyriou

  06/2010;

  We report a combined experimental and theoretical investigation of the layered antimonide PrMnSbO which is isostructural to the parent phase of the iron pnictide superconductors. We find linearWe report a combined experimental and theoretical investigation of the layered antimonide PrMnSbO which is isostructural to the parent phase of the iron pnictide superconductors. We find linear resistivity near room temperature and Fermi liquid-like T^{2} behaviour below 150 K. Neutron powder diffraction shows that unfrustrated C-type Mn magnetic order develops below \sim 230 K, followed by a spin-flop coupled to induced Pr order. At T \sim 35 K, we find a tetragonal to orthorhombic (T-O) transition. First principles calculations show that the large magnetic moments observed in this metallic compound are of local origin. Our results are thus inconsistent with either the itinerant or frustrated models proposed for symmetry breaking in the iron pnictides. We show that PrMnSbO is instead a rare example of a metal where structural distortions are driven by f-electron degrees of freedom.

• Synthesis and reactivity of ferrocenyl functionalized Sn/S cages.

  Authors: Christopher Pöhlker, Inga Schellenberg, Rainer Pöttgen, Stefanie Dehnen

  Chemical communications (Cambridge, England). 04/2010; 46(15):2605-7.

  Depending on the solvent used, the mono-stannylated FcSnCl(3) (1) reacts with Na(2)S to give ionic [Na(6)(Me(2)CO)(4)(OH(2))(6)] [(FcSn)(3)S(6)](2) (2), with a yet unprecedented thiostannate anion,Depending on the solvent used, the mono-stannylated FcSnCl(3) (1) reacts with Na(2)S to give ionic [Na(6)(Me(2)CO)(4)(OH(2))(6)] [(FcSn)(3)S(6)](2) (2), with a yet unprecedented thiostannate anion, or the adamantane-type Sn/S-cluster [(FcSn)(4)S(6)] (3). Complex 2 reacts readily with [Ni(acac)(2)], yielding the mixed-metallic complex [{Na(thf)(3.5)}(2){(FcSn)(8)Ni(3)S(16)}] x 2 THF (4 x 2 THF); the structures of 1-4 are discussed as well as Mössbauer spectra.

• The formation of a metalloid Sn(10)[Si(SiMe(3))(3)](6) cluster compound and its relation to the alpha<-->beta tin phase transition.

  Authors: Claudio Schrenk, Inga Schellenberg, Rainer Pöttgen, Andreas Schnepf

  Dalton transactions (Cambridge, England : 2003). 02/2010; 39(7):1872-6.

  Very recently it was shown that Sn monohalides can be prepared in preparative scale applying a preparative co-condensation technique. Here, a first reaction of Sn(i)Br is presented leading to theVery recently it was shown that Sn monohalides can be prepared in preparative scale applying a preparative co-condensation technique. Here, a first reaction of Sn(i)Br is presented leading to the metalloid cluster compound Sn(10)[Si(SiMe(3))(3)](6) 1. This reaction can be seen as a first step to metalloid cluster compounds applying the disproportionation reaction of a metastable Sn monohalide. The ten tin atoms in 1 are arranged in the form of a centaur polyhedron, representing a novel structural motif in tin chemistry. The structural and electronic properties of 1 and its relation to the phase transition alpha<-->beta tin are discussed with the aid of quantum chemical calculations as well as (119)Sn Mössbauer spectroscopy.

• The Subtle Influence of Binary versus Homoatomic Zintl Ions: The Phenyl-Ligated Trimetallic Cage [Sn(2)Sb(5)(ZnPh)(2)](3-).

  Authors: Felicitas Lips, Inga Schellenberg, Rainer Pöttgen, Stefanie Dehnen

  Chemistry (Weinheim an der Bergstrasse, Germany). 10/2009;

• Low Temperature Crystal Structure and 57Fe Moessbauer Spectroscopy of Sr3Sc2O5Fe2As2

  Authors: Marcus Tegel, Inga Schellenberg, Franziska Hummel, Rainer Poettgen, Dirk Johrendt

  05/2009;

  The crystal structure of the layered iron arsenide Sr3Sc2O5Fe2As2 was determined between 300 and 10 K. The lattice parameters of the tetragonal cell decrease anisotropically according to delta(c)/c :The crystal structure of the layered iron arsenide Sr3Sc2O5Fe2As2 was determined between 300 and 10 K. The lattice parameters of the tetragonal cell decrease anisotropically according to delta(c)/c : delta(a)/a = 4.2, which results in a slight flattening of the As-Fe-As bond angle within the FeAs layers. No indication of a structural instability could be detected. 57Fe Moessbauer spectroscopic data show a single signal at 4.2, 77, and 298 K, respectively, subjected to quadrupole splitting. The isomer shift increases from 0.36(1) mm/s at 298 K to 0.49(1) mm/s at 4.2 K. No indication for magnetic ordering was found. Comment: 12 pages, 4 figures

• The layered iron arsenides Sr2CrO3FeAs and Ba2ScO3FeAs

  Authors: Marcus Tegel, Franziska Hummel, Sebastian Lackner, Inga Schellenberg, Rainer Poettgen, Dirk Johrendt

  04/2009;

  Polycrystalline samples of the layered iron arsenides Sr2CrO3FeAs and Ba2ScO3FeAs were synthesized by high temperature solid state reactions and their crystal structures determined by the X-rayPolycrystalline samples of the layered iron arsenides Sr2CrO3FeAs and Ba2ScO3FeAs were synthesized by high temperature solid state reactions and their crystal structures determined by the X-ray powder diffraction. Their structures are tetragonal (P4/nmm; Sr2CrO3FeAs: a = 391.12(1) pm, c = 1579.05(3) pm; Ba2ScO3FeAs: a = 412.66(5) pm, c = 1680.0(2) pm, Z = 2) and isotypic to Sr2ScO3CuS. Iron arsenide layers are sandwiched between perowskite-like oxide blocks and separated by ~1600 pm, which is much larger compared to the 1111 iron arsenide superconductors. The bond length and angles within the FeAs layers are adapted to the space requirements of the oxide blocks. Measurements of the magnetic susceptibility and electrical resistivity show no hint for a SDW-like anomaly in both compounds. Sr2CrO3FeAs shows Curie-Weiss paramagnetism above 160 K with an effective magnetic moment of 3.83(3) muB in good agreement with the theoretical value of 3.87 muB for Cr3+. Antiferromagnetic ordering was detected below TN ~ 31 K. 57Fe Moessbauer spectra of Sr2CrO3FeAs show a single signal that broadens below the magnetic ordering temperature due to a small transferred hyperfine field induced by the magnetic ordering of the chromium atoms. 57Fe-Moessbauer spectra of Ba2ScO3FeAs show single signals at 298, 77, and 4.2 K which are only subject to weak quadrupole splitting. Comment: substantial addititions and corrections, references updated 19 pages, 7 figures

• Competition of magnetism and superconductivity in underdoped (Ba1-xKx)Fe2As2

  Authors: Marianne Rotter, Marcus Tegel, Inga Schellenberg, Falko M. Schappacher, Rainer Poettgen, Joachim Deisenhofer, Axel Guenther, Florian Schrettle, Alois Loidl, Dirk Johrendt

  01/2009;

  Polycrystalline samples of underdoped (Ba1-xKx)Fe2As2 (x<=0.4) were synthesized and studied by x-ray powder diffraction, magnetic susceptibility, specific heat and 57Fe-Moessbauer-spectroscopy. ThePolycrystalline samples of underdoped (Ba1-xKx)Fe2As2 (x<=0.4) were synthesized and studied by x-ray powder diffraction, magnetic susceptibility, specific heat and 57Fe-Moessbauer-spectroscopy. The structural phase transition from tetragonal to orthorhombic lattice symmetry shifts towards lower temperatures, becomes less pronounced at x = 0.1-0.2 and is no longer present at x = 0.3. Bulk superconductivity is observed in all samples except (Ba0.9K0.1)Fe2As2 by resistivity and magnetic susceptibility measurements. Specific heat data show a broad SDW phase transition in (Ba0.9K0.1)Fe2As2, which is hardly discernible in (Ba0.8K0.2)Fe2As2. No SDW anomaly is found in the specific heat of optimally doped (Ba0.6K0.4)Fe2As2, where C changes by 0.1 J/K at Tc = 37.3 K. 57Fe-Moessbauer-spectra show full magnetic hyperfine field splitting, indicative of antiferromagnetic ordering at 4.2 K in samples with x = 0-0.2, but zero magnetic hyperfine field in samples with x = 0.3. The spectra of (Ba0.9K0.1)Fe2As2 and (Ba0.8K0.2)Fe2As2 in the phase transition regions are temperature-dependent superpositions of magnetic and non-magnetic components, caused by inhomogeneous potassium distribution. Our results suggest the co-existence of AF magnetic ordering and superconductivity without mesoscopic phase separation in the underdoped region and show unambiguously homogeneous superconducting phases close to optimal doping. This is in contrast to recently reported results about single crystal (Ba1-xKx)Fe2As2.

• Spin density wave anomaly at 140 K in the ternary iron arsenide BaFe2As2

  Authors: Marianne Rotter, Marcus Tegel, Inga Schellenberg, Wilfried Hermes, Rainer Pöttgen, Dirk Johrendt

  06/2008;

  The ternary iron arsenide BaFe2As2 with the tetragonal ThCr2Si2-type structure exhibits a spin density wave (SDW) anomaly at 140 K, very similar to LaFeAsO, the parent compound of the iron arsenideThe ternary iron arsenide BaFe2As2 with the tetragonal ThCr2Si2-type structure exhibits a spin density wave (SDW) anomaly at 140 K, very similar to LaFeAsO, the parent compound of the iron arsenide superconductors. BaFe2As2 is a poor Pauli-paramagnetic metal and undergoes a structural and magnetic phase transition at 140 K, accompanied by strong anomalies in the specific heat, electrical resistance and magnetic susceptibility. In the course of this transition, the space group symmetry changes from tetragonal (I4/mmm) to orthorhombic (Fmmm). 57Fe Moessbauer spectroscopy experiments show a single signal at room temperature and full hyperfine field splitting below the phase transition temperature (5.2 T at 77 K). Our results suggest that BaFe2As2 can serve as a new parent compound for oxygen-free iron arsenide superconductors.

• A 57Fe Moessbauer Spectroscopy Study of the 7 K Superconductor LaFePO

  Authors: Marcus Tegel, Inga Schellenberg, Rainer Pöttgen, Dirk Johrendt

  06/2008;

  A polycrystalline sample of superconducting LaFePO was prepared in a tin flux at 1123 K. The structure was determined from single crystal data (ZrCuSiAs-type, P4/nmm, a = 3.9610(1), c = 8.5158(2) A,A polycrystalline sample of superconducting LaFePO was prepared in a tin flux at 1123 K. The structure was determined from single crystal data (ZrCuSiAs-type, P4/nmm, a = 3.9610(1), c = 8.5158(2) A, Z = 2) and the phase analysis was performed by the Rietveld method. LaFePO is Pauli-paramagnetic and becomes superconducting at 7 K after removing the ferromagnetic impurity phase Fe2P from the sample. 57Fe Moessbauer spectroscopy measurements at 298, 77, 4.2 and 4 K show single signals at isomer shifts around 0.35 mm/s, subject to weak quadrupole splitting. At 4 K, a symmetric line broadening appears, resulting from a small transferred magnetic hyperfine field of 1.15(1) T and accompanied by an angle of 54.7(5) between Bhf and Vzz, the main component of the electric field gradient tensor.

• Structural and 121Sb M\"ossbauer Spectroscopic Investigations of the Antimonide Oxides REMnSbO (RE = La, Ce, Pr, Nd, Sm, Gd, Tb) and REZnSbO (RE = La, Ce, Pr)

  Authors: Inga Schellenberg, Tom Nilges, Rainer Pöttgen

  05/2008;

  The quaternary antimonide oxides REMnSbO (RE = La, Ce, Pr, Nd, Sm, Gd, Tb) and REZnSbO (RE = La, Ce, Pr) were synthesized from the RESb monoantimonides and MnO, respectively ZnO. We report on singleThe quaternary antimonide oxides REMnSbO (RE = La, Ce, Pr, Nd, Sm, Gd, Tb) and REZnSbO (RE = La, Ce, Pr) were synthesized from the RESb monoantimonides and MnO, respectively ZnO. We report on single crystal X-ray data and a detailed 121Sb M\"ossbauer spectroscopic investigation.

• New quaternary hydride CeZnSnH_1.5 : structure, Magnetism, and chemical bonding

  Authors: Wilfried Hermes, Bernard Chevalier, Ute Ch. Rodewald, Samir F. Matar, François Weill, Inga Schellenberg, Rainer Pöttgen, Heiko Lueken, Manfred Speldrich

  Chemistry of Materials.

  The quaternary hydride CeZnSnH1.5 was synthesized from a CeZnSn precursor upon hydrogenation at 553 K and 4 MPa H2 pressure. Single-crystal X-ray diffraction data reveal that the metal atoms adopt anThe quaternary hydride CeZnSnH1.5 was synthesized from a CeZnSn precursor upon hydrogenation at 553 K and 4 MPa H2 pressure. Single-crystal X-ray diffraction data reveal that the metal atoms adopt an YPtAs-type structure: P63/mmc, a = 449.34(9) and c = 1731.3(4) pm, wR2 = 0.0493, 218 F2 values, and 12 variables. The hydrogen atoms fill three crystallographically independent ZnCe3 tetrahedral sites, leading to the composition CeZnSnH1.5. Hydrogenation anisotropically modifies the unit cell parameters, i.e., 456.7 → 449.34 pm (−1.6%) for a and 1673.8 → 1731.3 pm (+3.4%) for c. This leads to a drastic flattening of the two-dimensional [ZnSn] layers and a decrease of the Zn−Sn distances from 271 to 260 pm. Hydrogenation increases the Curie temperature from 4.8 K for CeZnSn to 7.3 K for CeZnSnH1.5.