Aaltodoc Repository :: Browsing by Author "Karttunen, Antti J."

Browsing by Author "Karttunen, Antti J."

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A 1D Coordination Polymer of UF5 with HCN as a Ligand
(2017-01-05) Scheibe, Benjamin; Rudel, Stefan S.; Buchner, Magnus R.; Karttunen, Antti J.; Kraus, Florian; University of Marburg; Department of Chemistry; Department of Chemistry and Materials Science
β-Uranium(V) fluoride was reacted with liquid anhydrous hydrogen cyanide to obtain a 1D coordination polymer with the composition (Formula presented.) [UF5(HCN)2], (Formula presented.) [UF4/1F2/2- (HCN)2/1], revealed by single-crystal X-ray structure determination. The reaction system was furthermore studied by means of vibrational and NMR spectroscopy, as well as by quantum chemical calculations. The compound presents the first described polymeric HCN Lewis adduct and the first HCN adduct of a uranium fluoride.
Ab initio computational study on the lattice thermal conductivity of Zintl clathrates [Si19 P4]Cl4 and Na4[Al4Si19]
(2016-08-17) Härkönen, Ville J.; Karttunen, Antti J.; University of Jyväskylä; Department of Chemistry
The lattice thermal conductivity of silicon clathrate framework Si23 and two Zintl clathrates, [Si19P4]Cl4 and Na4[Al4Si19], is investigated by using an iterative solution of the linearized Boltzmann transport equation in conjunction with ab initio lattice dynamical techniques. At 300 K, the lattice thermal conductivities for Si23, [Si19P4]Cl4, and Na4[Al4Si19] were found to be 43 W/(m K), 25 W/(m K), and 2 W/(m K), respectively. In the case of Na4[Al4Si19], the order-of-magnitude reduction in the lattice thermal conductivity was found to be mostly due to relaxation times and group velocities differing from Si23 and [Si19P4]Cl4. The difference in the relaxation times and group velocities arises primarily due to the phonon spectrum at low frequencies, resulting eventually from the differences in the second-order interatomic force constants (IFCs). The obtained third-order IFCs were rather similar for all materials considered here. The present findings are similar to those obtained earlier for some skutterudites. The predicted lattice thermal conductivity of Na4[Al4Si19] is in line with the experimentally measured thermal conductivity of recently synthesized type-I Zintl clathrate Na8[Al8Si38] (polycrystalline samples).
Aliovalent substitution in phosphide-based materials – Crystal structures of Na10AlTaP6 and Na3GaP2 featuring edge-sharing EP4 tetrahedra (E=Al/Ta and Ga)
(WILEY-V C H VERLAG GMBH, 2021-09-27) Restle, Tassilo M. F.; Zeitz, Sabine; Meyer, Jan; Klein, Wilhelm; Raudaschl-Sieber, Gabriele; Karttunen, Antti J.; Fässler, Thomas F.; Department of Chemistry and Materials Science; Inorganic Materials Modelling; Technical University of Munich
Recently, ternary lithium phosphides have been studied intensively owing to their high lithium ion conductivities. Much less is known about the corresponding sodium-containing compounds, and during investigations aiming for sodium phosphidotrielates, two new compounds have been obtained. The sodium phosphidoaluminumtantalate Na10AlTaP6, at first obtained as a by-product from the reaction with the container material, crystallizes in the monoclinic space group P21/n (no. 14) with lattice parameters of a=8.0790(3) Å, b=7.3489(2) Å, c=13.2054(4) Å, and β=90.773(2)°. The crystal structure contains dimers of edge-sharing [(Al0.5Ta0.5)P4] tetrahedra with a mixed Al/Ta site. DFT calculations support the presence of this type of arrangement instead of homonuclear Al2P6 or Ta2P6 dimers. The 31P and 23Na MAS NMR as well as the Raman spectra confirm the structure model. The assignment of the chemical shifts is confirmed applying the DFT-PBE method on the basis of the ordered structural model with mixed AlTaP6 dimers. The sodium phosphidogallate Na3GaP2 crystallizes in the orthorhombic space group Ibam (no. 72) with lattice parameters of a=13.081(3) Å, b=6.728(1) Å, and c=6.211(1) Å and is isotypic to Na3AlP2. Na3GaP2 exhibits linear chains of edge-sharing 1∞[GaP4/2] tetrahedra. For both compounds band structure calculations predict indirect band gaps of 2.9 eV.
Anionic Siliconoids from Zintl Phases: R3Si9 − with Six and R2Si9 2− with Seven Unsubstituted Exposed Silicon Cluster Atoms (R=Si(tBu)2H)
(2018-12-20) Schiegerl, Lorenz J.; Karttunen, Antti J.; Klein, Wilhelm; Fässler, Thomas F.; Department of Chemistry and Materials Science; Inorganic Materials Modelling; Technische Universität München
Neutral and anionic silicon clusters (siliconoids) are regarded as important model systems for bulk silicon surfaces. For 25 years their formation from binary alkali metal silicide phases has been proposed, but experimentally never realized. Herein the silylation of a silicide, leading to the anionic siliconoids (Si(tBu)2H)3Si9 − (1 a) and (Si(tBu)2H)2Si9 2− (2 a) with the highest known number of ligand-free silicon atoms is reported for the first time. The new anions are obtained in a one-step reaction of K12Si17/NH3(liq.) and Si(tBu)2HCl/THF. Electrospray ionization spectrometry and 1H, 13C, 29Si, as well as 29Si-HMBC (heteronuclear multiple bond correlation) NMR spectroscopy, confirm the attachment of three silyl groups at a [Si9]4− cluster under formation of 1 a, in accordance with calculated NMR shifts. During crystal growth the siliconoid di-anion 2 a is formed. The single-crystal X-ray structure determination reveals that two silyl groups are connected to the deltahedral Si9 cluster core, revealing seven unsubstituted exposed silicon cluster atoms with a hemispheroidal coordination. The negative charges −1 and −2 are delocalized over the six and seven siliconoid Si atoms in 1 a and 2 a, respectively.
Atomic-level structural and electronic properties of hybrid inorganic-organic ZnO:hydroquinone superlattices fabricated by ALD/MLD
(2015) Karttunen, Antti J.; Tynell, Tommi; Karppinen, Maarit; Department of Chemistry
Atomic/molecular layer deposition and electrochemical performance of dilithium 2-aminoterephthalate
(Royal Society of Chemistry, 2020-02-07) Heiska, Juho; Nisula, Mikko; Rautama, Eeva-Leena; Karttunen, Antti J.; Karppinen, Maarit; Department of Chemistry and Materials Science; School services, CHEM; Inorganic Materials Chemistry; Inorganic Materials Modelling
Control of the redox potential of lithium terephthalate Li2TP anode material is demonstrated by functionalizing its terephthalate backbone with an electron-donating amino group; this lowers - as intended - the redox potential of Li2TP by 0.14 V. The two Li-organic electrode materials, Li2TP and Li2TP-NH2, are fabricated as crystalline thin films from gaseous precursors using the atomic/molecular layer deposition (ALD/MLD) technique. The amino-functionalized material possesses a previously unknown crystal structure, addressed here by applying the USPEX evolutionary algorithm for the structure prediction and then LeBail fitting of the experimental XRD pattern based on the predicted structure model. The ALD/MLD fabrication yields in situ lithiated active electrode materials without any conductive additivies or binders and thus allows a straightforward evaluation of their intrinsic electrochemical properties. Comparison between Li2TP and its amino-functionalized derivative reveals inferior capacity retention and rate capability characteristics for the latter, which somewhat counterveils the pros-and-cons balance between the two Li-organic electrode materials. From galvanostatic cycling experiments and post-mortem XRD and SEM analysis, the issue with Li2TP-NH2 is revealed to be in the morphology changes occurring during the discharge/charge cycling.
Ba12[BN2]6.67H4: A Disordered Anti-Skutterudite filled with Nitridoborate Anions
(Wiley-VCH Verlag, 2024-01-22) Wandelt, Sophia L.; Mutschke, Alexander; Khalyavin, Dmitry; Steinadler, Jennifer; Karttunen, Antti J.; Schnick, Wolfgang; Department of Chemistry and Materials Science; Inorganic Materials Modelling; Ludwig Maximilian University of Munich; Technical University of Munich; Rutherford Appleton Laboratory
Skutterudites are of high interest in current research due to their diversity of structures comprising empty, partially filled and filled variants, mostly based on metallic compounds. We herein present Ba12[BN2]6.67H4, forming a non-metallic filled anti-skutterudite. It is accessed in a solid-state ampoule reaction from barium subnitride, boron nitride and barium hydride at 750 °C. Single-crystal X-ray and neutron powder diffraction data allowed to elucidate the structure in the cubic space group Im (Formula presented.) (no. 204). The barium and hydride atoms form a three-dimensional network consisting of corner-sharing HBa6 octahedra and Ba12 icosahedra. Slightly bent [BN2]3− units are located in the icosahedra and the voids in-between. 1H and 11B magic angle spinning (MAS) NMR experiments and vibrational spectroscopy further support the structure model. Quantum chemical calculations coincide well with experimental results and provide information about the electronic structure of Ba12[BN2]6.67H4.
Binary Lead Fluoride Pb3F8
(WILEY-V C H VERLAG GMBH, 2019-12-05) Deubner, H. Lars; Sachs, Malte; Bandemehr, Jascha; Ivlev, Sergei I.; Karttunen, Antti J.; Kachel, Stefan R.; Klein, Benedikt P.; Ruppenthal, Lukas; Schöniger, Maik; Krug, Claudio K.; Herritsch, Jan; Gottfried, J. Michael; Aman, Jamal N.M.; Schmedt auf der Günne, Jörn; Kraus, Florian; Department of Chemistry and Materials Science; Inorganic Materials Modelling; University of Marburg; University of Siegen
The binary lead fluoride Pb3F8 was synthesized by the reaction of anhydrous HF with Pb3O4 or by the reaction of BrF3 with PbF2. The compound was characterized by single-crystal and powder X-ray diffraction, IR, Raman, and solid-state MAS 19F NMR spectroscopy, as well as thermogravimetric analysis, XP and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Solid-state quantum-chemical calculations are provided for the vibrational analyses and band assignments. The electronic band structure offers an inside view of the mixed valence compound.
Boranyl-Functionalized [Ge9] Clusters : Providing the Idea of Intramolecular Ge/B Frustrated Lewis Pairs
(WILEY-V C H VERLAG GMBH, 2021-02-01) Wallach, Christoph; Geitner, Felix S.; Karttunen, Antti J.; Fässler, Thomas F.; Department of Chemistry and Materials Science; Inorganic Materials Modelling; Technical University of Munich
The unique three-dimensional structure of spherical, homoatomic nine-atom germanium clusters opens various possibilities for the spatial arrangement of functional groups. Ligands comprising lone pairs have recently been introduced in the cluster sphere, and we now report the addition of a boranyl group to the cluster featuring a Ge−B exo-cluster bond. The reaction of the twofold-silylated cluster [Ge9{Si(TMS)3}2]2− (TMS=trimethylsilyl) with 2-chloro-1,3,2-diazaborolidines DABR-Cl leads to the first boranyl-functionalized [Ge9] clusters [Ge9{Si(TMS)3}2DABR]− (R=methyl (1 a), iso-propyl (2 a), ortho-tolyl (3 a)). The anions 2 a and 3 a were structurally characterized as [NHCDippCu]+ complexes (NHCDipp=1,3-di(2,6-diisopropylphenyl)imidazolylidine) through single crystal X-ray structure determination. Quantum-chemical calculations manifest the frustrated Lewis pair (FLP) character of the boranyl-functionalized cluster [Ge9{Si(TMS)3}2BCy2]− (4 a).
Borate Hydrides as a New Material Class : Structure, Computational Studies, and Spectroscopic Investigations on Sr5(BO3)3H and Sr5(11BO3)3D
(WILEY-V C H VERLAG GMBH, 2020-09-10) Wylezich, Thomas; Valois, Renaud; Suta, Markus; Mutschke, Alexander; Ritter, Clemens; Meijerink, Andries; Karttunen, Antti J.; Kunkel, Nathalie; Department of Chemistry and Materials Science; Inorganic Materials Modelling; University of Göttingen; Université d'Artois; Utrecht University; Technische Universität München; Institut Laue-Langevin
The unprecedented borate hydride Sr5(BO3)3H and deuteride Sr5(11BO3)3D crystallizing in an apatite-related structure are reported. Despite the presence of hydride anions, the compound decomposes only slowly in air. Doped with Eu2+, it shows broad-band orange-red emission under violet excitation owing to the 4f65d–4f7 transition of Eu2+. The observed 1H NMR chemical shift is in good agreement with previously reported 1H chemical shifts of ionic metal hydrides as well as with quantum chemical calculations and very different from 1H chemical shifts usually found for hydroxide ions in similar materials. FTIR and Raman spectroscopy of different samples containing 1H, 2H, natB, and 11B combined with calculations unambiguously prove the absence of hydroxide ions and the sole incorporation of hydride ions into the borate. The orange-red emission obtained by doping with Eu2+ shows that the new compound class might be a promising host material for optical applications.
[Br4F21]− - a unique molecular tetrahedral interhalogen ion containing a μ4-bridging fluorine atom surrounded by BrF5 molecules
(Royal Society of Chemistry, 2024-03-07) Möbs, Martin; Graubner, Tim; Karttunen, Antti J.; Kraus, Florian; Department of Chemistry and Materials Science; Inorganic Materials Modelling; University of Marburg
The reaction of [NMe4][BrF6] with an excess of BrF5 leads to the compound [NMe4][Br4F21]·BrF5. It features molecular [(μ4-F)(BrF5)4]− anions of tetrahedron-like shape containing central μ4-bridging F atoms coordinated by four BrF5 molecules. It is the most BrF5-rich fluoridobromate anion by mass. Quantum-chemical calculations showed that the μ4-F-Br bonds within the anion are essentially ionic in nature. The compound is the first example where F atoms bridge μ4-like neither to metal nor to hydrogen atoms. It was characterized by Raman spectroscopy and by single-crystal X-ray diffraction. The latter showed surprisingly that its crystal structure is related to the intermetallic half-Heusler compound and structure type MgAgAs.
Bridging the Junction: Electrical Conductivity of Carbon Nanotube Networks
(AMERICAN CHEMICAL SOCIETY, 2022-10-13) Conley, Kevin; Karttunen, Antti J.; Department of Chemistry and Materials Science; Inorganic Materials Modelling
Carbon nanotube (CNT) films have excellent conductivity and suitable flexibility for chemical sensing and touch screen devices. Understanding the pathways of charge transport within the network is crucial to develop new functional materials and improve existing devices. Here, we study the electrical conductivity of networks of CNTs containing Group 11 metals (Au, Ag, and Cu), s-p metals (K, Ca, and Al), AuCl3, AuCl4, and Cl using quantum mechanical methods and semiclassical Boltzmann transport theory. The conductivity is characterized along the nanotubes and across the intersecting junction. The conductivity is much weaker across the junction than along the nanotubes and could be strengthened in all directions using dopants. The largest increase in conductivity is induced by Al along the nanotubes and by Cu across the intersection [389-fold and 14-fold relative to the pristine (8,0) network, respectively]. Additionally, Ag dopants activate charge transport along the semiconducting nanotube in heterogeneous networks of mixed metal and semiconducting nanotubes. The conductivity along the semiconducting nanotube increased 781-fold. This activation removes the bottleneck of charge transport along the semiconducting nanotubes within the network of mixed chiralities. Small amounts of dopants within nanotube networks drastically change the directional conductivity and provide new pathways for charge transport for applications such as chemical sensing or touch screens.
A brief visit to the BeCl2/ZnCl2 system and the prediction of a new polymorph of ZnCl2
(Verlag der Zeitschrift fur Naturforschung, 2020-05) Deubner, H. Lars; Bandemehr, Jascha; Karttunen, Antti J.; Kraus, Florian; Department of Chemistry and Materials Science; Inorganic Materials Modelling; University of Marburg
Reactions of zinc chloride with beryllium chloride in the molar ratios of 1:1 and 3:2 at T = 300°C in sealed ampoules lead to the formation of the two compounds Be1- xZnxCl2 (x = 0.563(2) and 0.489(3), respectively). Their composition and crystal structures were evidenced by single crystal X-ray structure analysis. Both compounds crystallize isotypic to β-BeCl2 in the tetragonal space group I41/acd, No. 142, tI96, with a = 10.7548(1), c = 19.4656(5) Å, V = 2251.50(7) Å3, Z = 32 at T = 100 K for the first and a = 10.7511(3), c = 19.2335(10) Å, V = 2223.1(2) Å3, Z = 32 at T = 100 K for the second compound. The positions of the Be atoms are mixed-occupied by Zn atoms. The compounds were additionally characterized by powder X-ray diffraction and infrared spectroscopy. Plots according to Vegard's law allowed for extrapolation towards a neat ZnCl2 phase that would crystallize in the β-BeCl2 structure, which is the ZnI2 structure type. Quantum chemical calculations have confirmed that such a ZnCl2 modification would represent a true local minimum.
Bromine Pentafluoride BrF5, the Formation of [BrF6]− Salts, and the Stereochemical (In)activity of the Bromine Lone Pairs
(WILEY-VCH VERLAG, 2022-12-27) Möbs, Martin; Graubner, Tim; Eklund, Kim; Karttunen, Antti J.; Kraus, Florian; Department of Chemistry and Materials Science; Inorganic Materials Modelling; University of Marburg
BrF5 can be prepared by treating BrF3 with fluorine under UV light in the region of 300 to 400 nm at room temperature. It was analyzed by UV-Vis, NMR, IR and Raman spectroscopy. Its crystal structure was redetermined by X-ray diffraction, and its space group was corrected to Pnma. Quantum-chemical calculations were performed for the band assignment of the vibrational spectra. A monoclinic polymorph of BrF5 was quantum chemically predicted and then observed as its low-temperature modification in space group P21/c by single crystal X-ray diffraction. BrF5 reacts with the alkali metal fluorides AF (A=K, Rb) to form alkali metal hexafluoridobromates(V), A[BrF6] the crystal structures of which have been determined. Both compounds crystallize in the K[AsF6] structure type (R (Formula presented.), no. 148, hR24). For the species [BrF6]+, BrF5, [BrF6]−, and [IF6]−, the chemical bonds and lone pairs on the heavy atoms were investigated by means of intrinsic bond orbital analysis.
Centrosymmetric to non-centrosymmetric transition in the Ca2−xMnxTi2O6 double perovskite system studied through structural analysis and dielectric properties
(Royal Society of Chemistry, 2024-04-14) Albrecht, Elisabeth K.; Siponkoski, Tuomo; Rautama, Eeva-Leena; Karppinen, Maarit; Karttunen, Antti J.; Department of Chemistry and Materials Science; Inorganic Materials Modelling; Inorganic Materials Chemistry; University of Oulu
We have used high-pressure synthesis to synthesize samples of Ca2−xMnxTi2O6 double perovskite, where x varies between 0.2 and 1. The synthesized materials were structurally characterized with powder X-ray diffraction (XRD). Rietveld refinement of the XRD patterns was used to study the change from CaTiO3 (x = 0) to the composition CaMnTi2O6 (x = 1) where half of the Ca(ii) ions are replaced by smaller Mn(ii) ions. We analyzed the peak shapes in the XRD patterns, as well as lattice parameters, and it appears that smooth symmetry change from the centrosymmetric space group Pbnm to the non-centrosymmetric space group P42mc occurs between x = 0.3 and x = 0.5. We also confirmed the centrosymmetric to non-centrosymmetric transition by characterizing the dielectric properties of the materials with ferroelectric measurements.
Charged Si9 Clusters in Neat Solids and the Detection of [H2Si9]2− in Solution: A Combined NMR, Raman, Mass Spectrometric, and Quantum Chemical Investigation
(2018-09-24) Schiegerl, Lorenz J.; Karttunen, Antti J.; Tillmann, Jan; Geier, Sebastian; Raudaschl-Sieber, Gabriele; Waibel, Markus; Fässler, Thomas F.; Department of Chemistry and Materials Science; Inorganic Materials Modelling; Technical University of Munich; Wacker Chemie AG
Polyanionic silicon clusters are provided by the Zintl phases K4Si4, comprising [Si4]4− units, and K12Si17, consisting of [Si4]4− and [Si9]4− clusters. A combination of solid-state MAS-NMR, solution NMR, and Raman spectroscopy, electrospray ionization mass spectrometry, and quantum-chemical investigations was used to investigate four- and nine-atomic silicon Zintl clusters in neat solids and solution. The results were compared to 29Si isotope-enriched samples. 29Si-MAS NMR and Raman shifts of the phase-pure solids K4Si4 and K12Si17 were interpreted by quantum-chemical calculations. Extraction of [Si9]4− clusters from K12Si17 with liquid ammonia/222crypt and their transfer to pyridine yields in a red solid containing Si9 clusters. This compound was characterized by elemental and EDX analyses and 29Si-MAS NMR and Raman spectroscopy. Charged Si9 clusters were detected by 29Si NMR in solution. 29Si and 1H NMR spectra reveal the presence of the [H2Si9]2− cluster anion in solution.
Chemi-Inspired Silicon Allotropes—Experimentally Accessible Si9 Cages as Proposed Building Block for 1D Polymers, 2D Sheets, Single-Walled Nanotubes, and Nanoparticles
(MDPI AG, 2022-02-01) Jantke, Laura-Alice; Karttunen, Antti J.; Fässler, Thomas F.; Department of Chemistry and Materials Science; Inorganic Materials Modelling; Technical University of Munich
Numerous studies on silicon allotropes with three-dimensional networks or as materials of lower dimensionality have been carried out in the past. Herein, allotropes of silicon, which are based on structures of experimentally accessible [Si9 ]4− clusters known as stable anionic molecular species in neat solids and in solution, are predicted. Hypothetical oxidative coupling under the formation of covalent Si–Si bonds between the clusters leads to uncharged two-, one-and zero-dimensional silicon nanomaterials not suffering from dangling bonds. A large variety of structures are derived and investigated by quantum chemical calculations. Their relative energies are in the same range as experimentally known silicene, and some structures are even energetically more favorable than silicene. Significantly smaller relative energies are reached by the insertion of linkers in form of tetrahedrally connected Si atoms. A chessboard pattern built of Si9 clusters bridged by tetrahedrally connected Si atoms represents a two-dimensional silicon species with remarkably lower relative energy in comparison with silicene. We discuss the structural and electronic properties of the predicted silicon materials and their building block nido-[Si9 ]4– based on density functional calculations. All considered structures are semiconductors. The band structures exclusively show bands of low dispersion, as is typical for covalent polymers.
Chemical Bonding and Crystal Structure Schemes in Atomic/Molecular Layer Deposited Fe-Terephthalate Thin Films
(American Chemical Society, 2024-07-09) Jussila, Topias; Philip, Anish; Rubio-Giménez, Víctor; Eklund, Kim; Vasala, Sami; Glatzel, Pieter; Lindén, Johan; Motohashi, Teruki; Karttunen, Antti J.; Ameloot, Rob; Karppinen, Maarit; Department of Chemistry and Materials Science; Inorganic Materials Chemistry; Inorganic Materials Modelling; KU Leuven; European Synchrotron Radiation Facility; Åbo Akademi University; Kanagawa University
Advanced deposition routes are vital for the growth of functional metal-organic thin films. The gas-phase atomic/molecular layer deposition (ALD/MLD) technique provides solvent-free and uniform nanoscale thin films with unprecedented thickness control and allows straightforward device integration. Most excitingly, the ALD/MLD technique can enable the in situ growth of novel crystalline metal-organic materials. An exquisite example is iron-terephthalate (Fe-BDC), which is one of the most appealing metal-organic framework (MOF) type materials and thus widely studied in bulk form owing to its attractive potential in photocatalysis, biomedicine, and beyond. Resolving the chemistry and structural features of new thin film materials requires an extended selection of characterization and modeling techniques. Here we demonstrate how the unique features of the ALD/MLD grown in situ crystalline Fe-BDC thin films, different from the bulk Fe-BDC MOFs, can be resolved through techniques such as synchrotron grazing-incidence X-ray diffraction (GIXRD), Mössbauer spectroscopy, and resonant inelastic X-ray scattering (RIXS) and crystal structure predictions. The investigations of the Fe-BDC thin films, containing both trivalent and divalent iron, converge toward a novel crystalline Fe(III)-BDC monoclinic phase with space group C2/c and an amorphous Fe(II)-BDC phase. Finally, we demonstrate the excellent thermal stability of our Fe-BDC thin films.
Coexistence of Two Different Distorted Octahedral [MnF6]3− Sites in K3[MnF6]: Manifestation in Spectroscopy and Magnetism
(WILEY-V C H VERLAG GMBH, 2021-07-07) Stoll, Christiane; Atanasov, Mihail; Bandemehr, Jascha; Neese, Frank; Pietzonka, Clemens; Kraus, Florian; Karttunen, Antti J.; Seibald, Markus; Heymann, Gunter; Huppertz, Hubert; Department of Chemistry and Materials Science; Inorganic Materials Modelling; University of Innsbruck; Max Planck Institute for Coal Research; University of Marburg; Osram Opto Semiconductors GmbH
As a consequence of the static Jahn-Teller effect of the 5E ground state of MnIII in cubic structures with octahedral parent geometries, their octahedral coordination spheres become distorted. In the case of six fluorido ligands, [MnF6]3− anions with two longer and four shorter Mn−F bonds making elongated octahedra are usually observed. Herein, we report the synthesis of the compound K3[MnF6] through a high-temperature approach and its crystallization by a high-pressure/high-temperature route. The main structural motifs are two quasi-isolated, octahedron-like [MnF6]3− anions of quite different nature compared to that met in ideal octahedral MnIII Jahn-Teller systems. Owing to the internal electric field of Ci symmetry dominated by the next-neighbour K+ ions acting on the MnIII sites, both sites, the pseudo-rhombic (site 1) and the pseudo-tetragonally elongated (site 2) [MnF6]3− anions are present in K3[MnF6]. The compound was characterized by single-crystal and powder X-ray diffraction, and magnetometry as well as by FTIR, Raman, and ligand field spectroscopy. A theoretical interpretation of the electronic structure and molecular geometry of the two Mn sites in the lattice is given by using a vibronic coupling model with parameters adjusted from multireference ab-initio cluster calculations.
A Combined Metal-Halide/Metal Flux Synthetic Route towards Type-I Clathrates: Crystal Structures and Thermoelectric Properties of A8Al8Si38 (A=K, Rb, and Cs)
(2014) Baran, Volodymyr; Senyshyn, Anatoliy; Karttunen, Antti J.; Fischer, Andreas; Scherer, Wolfgang; Raudaschl-Sieber, Gabriele; Fässler, Thomas F.; Department of Chemistry

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