117 results on '"Høgni Weihe"'
Search Results
2. [CrIII8NiII6]n+ Heterometallic Coordination Cubes
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Helen M. O’Connor, Sergio Sanz, Aaron J. Scott, Mateusz B. Pitak, Wim T. Klooster, Simon J. Coles, Nicholas F. Chilton, Eric J. L. McInnes, Paul J. Lusby, Høgni Weihe, Stergios Piligkos, and Euan K. Brechin
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molecular magnetism ,supramolecular chemistry ,heterometallic clusters ,magnetometry ,EPR spectroscopy ,Organic chemistry ,QD241-441 - Abstract
Three new heterometallic [CrIII8NiII6] coordination cubes of formulae [CrIII8NiII6L24(H2O)12](NO3)12 (1), [CrIII8NiII6L24(MeCN)7(H2O)5](ClO4)12 (2), and [CrIII8NiII6L24Cl12] (3) (where HL = 1-(4-pyridyl)butane-1,3-dione), were synthesised using the paramagnetic metalloligand [CrIIIL3] and the corresponding NiII salt. The magnetic skeleton of each capsule describes a face-centred cube in which the eight CrIII and six NiII ions occupy the eight vertices and six faces of the structure, respectively. Direct current magnetic susceptibility measurements on (1) reveal weak ferromagnetic interactions between the CrIII and NiII ions, with JCr-Ni = + 0.045 cm−1. EPR spectra are consistent with weak exchange, being dominated by the zero-field splitting of the CrIII ions. Excluding wheel-like structures, examples of large heterometallic clusters containing both CrIII and NiII ions are rather rare, and we demonstrate that the use of metalloligands with predictable bonding modes allows for a modular approach to building families of related polymetallic complexes. Compounds (1)–(3) join the previously published, structurally related family of [MIII8MII6] cubes, where MIII = Cr, Fe and MII = Cu, Co, Mn, Pd.
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- 2021
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3. Iridates from the molecular side
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Kasper S. Pedersen, Jesper Bendix, Alain Tressaud, Etienne Durand, Høgni Weihe, Zaher Salman, Thorbjørn J Morsing, Daniel N. Woodruff, Yanhua Lan, Wolfgang Wernsdorfer, Corine Mathonière, Stergios Piligkos, Sophia I. Klokishner, Serghei Ostrovsky, Katharina Ollefs, Fabrice Wilhelm, Andrei Rogalev, and Rodolphe Clérac
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Science - Abstract
Iridates are known to exhibit a range of exotic electronic and magnetic behaviours but it is difficult to prepare isolated [IrO6]8− species via soft chemical routes. Here, the authors isolate the isoelectronic [IrF6]2−complex, and assess it as a model and for iridate analogues.
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- 2016
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4. Crystal structure of trihydrogen bis{[1,1,1-tris(2-oxidoethylaminomethyl)ethane]cobalt(III)} trinitrate
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Waqas Sethi, Heini V. Johannesen, Thorbjørn J. Morsing, Stergios Piligkos, and Høgni Weihe
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crystal structure ,cobalt(III) complex ,1,1,1-tris(2-hydroxyethylaminomethyl)ethane ,hydrogen-bonding motif ,racemic conglomerate ,Crystallography ,QD901-999 - Abstract
The title compound, [Co2(L)2]3+·3NO3− [where L = CH3C(CH2NHCH2CH2OH1/2)3], has been synthesized from the ligand 1,1,1-tris(2-hydroxyethylaminomethyl)ethane. The cobalt(III) dimer has an interesting and uncommon O—H...O hydrogen-bonding motif with the three bridging hydroxy H atoms each being equally disordered over two positions. In the dimeric trication, the octahedrally coordinated CoIII atoms and the capping C atoms lie on a threefold rotation axis. The N atoms of two crystallographically independent nitrate anions also lie on threefold rotation axes. N—H...O hydrogen bonding between the complex cations and nitrate anions leads to the formation of a three-dimensional network structure. The compound is a racemic conglomerate of crystals containing either d or l molecules. The crystal used for this study is a d crystal.
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- 2015
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5. Synthesis and characterization of monomeric and dimeric manganese(II) and zinc(II) complexes of pyridine-2-carbaldoxime
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Jørgen Glerup, Patricia A. Goodson, Derek J. Hodgson, Kirsten Michelsen, Urszula Rychlewska, and Høgni Weihe
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Chemistry ,QD1-999 - Abstract
The syntheses and characterization of two complexes of manganese(II) and one complex of zinc(II) with the ligand pyridine-2-carbaldoxime, C6H6N2O, are described. The monomeric manganese(II) complex cis-[Mn(C6H6N2O) 2Cl2] (1) crystallizes in the orthorhombic space group Pbcn with 4 formula units in a cell of dimensions a = 12.479(3) Å, b = 10.348(2) Å, and c = 11. 974(2) Å. The structure has been refined to a final value of the conventional R-factor of 0.0330 based on 1513 observed independent reflections. The analogous zinc(II) complex, cis-[Zn(C6H6N2O)2Cl2] (2) also crystallizes in the orthorhombic space group Pbcn with 4 formula units in a cell of dimensions a = 12.215(2) Å, b = 10.383(2) Å, and c = 12. 016(2) Å. The structure has been refined to a final value of the conventional R-factor of 0.0377 based on 1117 observed independent reflections. The two complexes are isostructural, with the central metal atom lying on a crystallographic 2-fold axis. Both complexes are approximately octahedral, the coordination being provided by two trans pyridine nitrogen atoms and two cis amine nitrogen atoms from the oxime ligands, and by two cis chlorides. The dimeric manganese(II) complex [(C6H6N2O)(CH3OH)ClMnCl2MnCl(CH3OH)(C6H6N2O)] (3) crystallizes in the monoclinic space group P21/n with 2 formula units in a cell of dimensions a = 7.895(2) Å, b = 11.196(3) Å, and c = 12. 544(2) Å, and b = 98.39(2)o. The structure has been refined to a final value of the conventional R-factor of 0.0312 based on 1568 observed independent reflections. There is a crystallographic inversion center in the middle of the dimer relating one manganese center to the other. The geometry at each manganese(II) center is again roughly octahedral, coordination being provided by two nitrogen atoms from the oxime ligand, a terminal chloride ion trans to the amine nitrogen, the oxygen atom of the coordinated methanol molecule, and two bridging chlorides that link the two halves of the dimer. The Mn$$$Mn separation is 3.647(1) Å and the bridging Mn-Cl-Mn angle is 91.8(1)o. The temperature dependence of the magnetic susceptibility of 3 exhibits a maximum at approximately 8 K, indicative of a weak antiferromagnetic interaction between the two metal centers with J = 1.94(1) cm-1. The EPR spectrum of 1 diluted into the corresponding Zn(II) host has been fitted to the parameters g = 2.00, A = 0.0084 cm-1, D = 0.157 cm-1, and E = 0.0005 cm-1. The small value of E/D is consistent with the observed symmetry of the complex.
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- 2000
6. Erratum: Iridates from the molecular side
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Kasper S. Pedersen, Jesper Bendix, Alain Tressaud, Etienne Durand, Høgni Weihe, Zaher Salman, Thorbjørn J Morsing, Daniel N. Woodruff, Yanhua Lan, Wolfgang Wernsdorfer, Corine Mathonière, Stergios Piligkos, Sophia I. Klokishner, Serghei Ostrovsky, Katharina Ollefs, Fabrice Wilhelm, Andrei Rogalev, and Rodolphe Clérac
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Science - Abstract
Nature Communications 7: Article number: 12195 (2016); Published: 20 July 2016; Updated: 31 August 2016 The original version of this Article contained an error in which the first affiliation was incorrectly given as ‘CNRS, ICMCB, UPR 9048, Pessac 33600, France’. This has now been corrected in both the PDF and HTML versions of the Article.
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- 2016
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7. Dipolar-coupled entangled molecular 4f qubits
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Bela E. Bode, Edoardo Fusco, Rachel Nixon, Christian D. Buch, Høgni Weihe, Stergios Piligkos, BBSRC, University of St Andrews. EaSTCHEM, University of St Andrews. Biomedical Sciences Research Complex, University of St Andrews. Centre of Magnetic Resonance, and University of St Andrews. School of Chemistry
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Colloid and Surface Chemistry ,MCP ,DAS ,QD ,General Chemistry ,QD Chemistry ,Biochemistry ,Catalysis - Abstract
S.P. thanks the Novo Nordisk Foundation for research grant NNF20OC0065610. EPR Equipment funding by BBSRC to B. E. B. (17 Alert grant BB/R013780/1) is also gratefully acknowledged. We demonstrate by use of continuous wave- and pulse-electron paramagnetic resonance spectroscopy on oriented single crystals of magnetically dilute YbIII ions in Yb0.01Lu0.99(trensal) that molecular entangled two-qubit systems can be constructed by exploiting dipolar interactions between neighboring YbIII centers. Furthermore, we show that the phase memory time and Rabi frequencies of these dipolar-interaction-coupled entangled two-qubit systems are comparable to the ones of the corresponding single qubits. Publisher PDF
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- 2023
8. Unequal sensitivities of energy levels in a high-symmetry Ho
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Niels A, Bonde, Markus, Appel, Jacques, Ollivier, Høgni, Weihe, and Jesper, Bendix
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High-resolution inelastic neutron scattering has been used to study low-energy magnetic transitions in a Ho
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- 2022
9. Experimental assignment of long range magnetic communication through Pd amp; Pt metallophilic contacts
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Emil M. H. Larsen, Niels A. Bonde, Høgni Weihe, Jacques Ollivier, Tom Vosch, Thomas Lohmiller, Karsten Holldack, Alexander Schnegg, Mauro Perfetti, and Jesper Bendix
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CENTER-DOT-PT ,heterobimetalic lantern complexes ,HETEROBIMETALLIC LANTERN COMPLEXES ,SYMMETRY ,RELAXATION ,General Chemistry - Abstract
Record-breaking magnetic exchange interactions have previously been reported for 3d-metal dimers of the form [M(Pt(SAc)(4))(pyNO(2))](2) (M = Ni or Co) that are linked in the solid state via metallophilic PtMIDLINE HORIZONTAL ELLIPSISPt bridges. This contrasts the terminally capped monomers [M(Pt(SAc)(4))(py)(2)], for which neither metallophilic bridges nor magnetic exchange interactions are found. Computational modeling has shown that the magnetic exchange interaction is facilitated by the pseudo-closed shell d(8)MIDLINE HORIZONTAL ELLIPSISd(8) metallophilic interaction between the filled Pt2+ 5d(z)(2) orbitals. We present here inelastic neutron scattering experiments on these complexes, wherein the dimers present an oscillatory momentum-transfer-dependence of the magnetic transitions. This allows for the unequivocal experimental assignment of the distance between the coupled ions, which matches exactly the coupling pathway via the metallophilic bridges. Furthermore, we have synthesized and magnetically characterized the isostructural palladium-analogues. The magnetic coupling across the PdMIDLINE HORIZONTAL ELLIPSISPd bridge is found through SQUID-magnetometry and FD-FT THz-EPR spectroscopy to be much weaker than via the PtMIDLINE HORIZONTAL ELLIPSISPt bridge. The weaker coupling is traced to the larger radial extent of the 5d(z)(2) orbitals compared to that of the 4d(z)(2) orbitals. The existence of a palladium metallophilic interaction is evaluated computationally from potential surface cuts along the metal stretching direction. Similar behavior is found for the PdMIDLINE HORIZONTAL ELLIPSISPd and PtMIDLINE HORIZONTAL ELLIPSISPt-systems with clear minima along this coordinate and provide estimates for the force constant for this distortion. The estimated MMIDLINE HORIZONTAL ELLIPSISM stretching frequencies are found to match experimental observed, polarized bands in single-crystal Raman spectra close to 45 cm(-1). This substantiates the existence of energetically relevant PdMIDLINE HORIZONTAL ELLIPSISPd metallophilic interactions. The unique properties of both Pt2+ and Pd2+ constitutes an orthogonal reactivity, which can be utilized for steering both the direction and strength of magnetic interactions.
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- 2022
10. Detection and Characterization of a Novel Copper‐Dependent Intermediate in a Lytic Polysaccharide Monooxygenase
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Høgni Weihe, Benedikt M. Blossom, Bart van Oort, Roberta Croce, Ranjitha Singh, Claus Felby, Raushan Kumar Singh, Morten J. Bjerrum, Manish Kumar Tiwari, Poul Erik Jensen, and David A. Russo
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Reaction mechanism ,chemistry.chemical_element ,010402 general chemistry ,Photochemistry ,Polysaccharide ,01 natural sciences ,Catalysis ,Mixed Function Oxygenases ,law.invention ,chemistry.chemical_compound ,law ,Oxidizing agent ,Reactivity (chemistry) ,Cellulose ,Electron paramagnetic resonance ,chemistry.chemical_classification ,010405 organic chemistry ,Organic Chemistry ,Electron Spin Resonance Spectroscopy ,Hydrogen Peroxide ,General Chemistry ,Monooxygenase ,Combinatorial chemistry ,Copper ,0104 chemical sciences ,Kinetics ,chemistry ,Biocatalysis ,Thermoascus ,Oxidation-Reduction - Abstract
Lytic polysaccharide monooxygenases (LPMOs) are copper-containing enzymes capable of oxidizing crystalline cellulose and the enzyme has large practical application in the process of refining biomass. The LPMO catalytic mechanism still remains debated despite several proposed reaction mechanisms. Here, we report a long-lived intermediate (t½= 6 – 8 minutes) observed in an LPMO fromThermoascus aurantiacus(TaLPMO9A). The intermediate with a strong absorption around 420 nm is formed when reduced LPMO-Cu(I) reacts with H2O2. UV-vis absorption spectroscopy, electron paramagnetic resonance (EPR), and stopped-flow spectroscopy indicate that the observed long-lived intermediate involves the copper center and a nearby tyrosine (Tyr175). We propose that the reaction with H2O2first forms a highly reactive short-lived Cu(III)-intermediate which is subsequently transformed into the observed long-lived copper-dependent intermediate. Since sub-equimolar amount of H2O2to LPMO boosts oxidation of phosphoric acid swollen cellulose (PASC) suggests that the long-lived copper-dependent intermediate is part of the catalytic mechanism for LPMOs. The proposed mechanism offers new perspectives in the oxidative reaction mechanism of copper enzymes and hence for the biomass oxidation and the reactivity of copper in biological systems.
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- 2019
11. Importance of Axial Symmetry in Elucidating Lanthanide-Transition Metal Interactions
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Mikkel Sørensen, Niels Bonde, Stéphane Rols, Jonatan B. Petersen, Jesper Bendix, Mauro Perfetti, Jacques Ollivier, B. Fåk, Høgni Weihe, and Ulla Gro Nielsen
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Lanthanide ,010405 organic chemistry ,Chemistry ,Electron ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Ion ,Inorganic Chemistry ,Crystallography ,Character (mathematics) ,Transition metal ,Diamagnetism ,Physical and Theoretical Chemistry ,Axial symmetry - Abstract
In this paper, we experimentally study and model the electron donating character of an axial diamagnetic Pd2+ ion in four metalloligated lanthanide complexes of formula [PPh4][Ln{Pd(SAc)4}2] (SAc- = thioacetate, Ln = Tb, Dy, Ho, and Er). A global model encompassing inelastic neutron scattering, torque magnetometry, and dc magnetometry allows to precisely determine the energy level structure of the complexes. Solid state nuclear magnetic resonance reveals a less donating character of Pd2+ compared to the previously reported isostructural Pt2+-based complexes. Consequently, all complexes invariably show a lower crystal field strength compared to their Pt2+-analogues. The dynamic properties show an enhanced single molecule magnet behavior due to the suppression of quantum tunneling, in agreement with our model.
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- 2020
12. Modular [FeIII8MII6]n+ (MII = Pd, Co, Ni, Cu) Coordination Cages
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Stergios Piligkos, Priyanka Comar, Amgalanbaatar Baldansuren, Sergio Sanz, Nicholas F. Chilton, Helen M. O'Connor, Høgni Weihe, Paul J. Lusby, Eric J. L. McInnes, Mateusz B. Pitak, Simon J. Coles, and Euan K. Brechin
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010405 organic chemistry ,Chemistry ,Metal ions in aqueous solution ,010402 general chemistry ,01 natural sciences ,Magnetic susceptibility ,0104 chemical sciences ,Ion ,law.invention ,Inorganic Chemistry ,Metal ,Magnetization ,Crystallography ,law ,visual_art ,visual_art.visual_art_medium ,Antiferromagnetism ,Physical and Theoretical Chemistry ,Electron paramagnetic resonance ,Spectroscopy - Abstract
The reaction of the simple metalloligand [FeIIIL3] [HL = 1-(4-pyridyl)butane-1,3-dione] with a variety of different MII salts results in the formation of a family of heterometallic cages of formulae [FeIII8PdII6L24]Cl12 (1), [FeIII8CuII6L24(H2O)4Br4]Br8 (2), [FeIII8CuII6L24(H2O)10](NO3)12 (3), [FeIII8NiII6L24(SCN)11Cl] (4), and [FeIII8CoII6L24(SCN)10(H2O)2]Cl2 (5). The metallic skeleton of each cage describes a cube in which the FeIII ions occupy the eight vertices and the MII ions lie at the center of the six faces. Direct-current magnetic susceptibility and magnetization measurements on 3–5 reveal the presence of weak antiferromagnetic exchange between the metal ions in all three cases. Computational techniques known in theoretical nuclear physics as statistical spectroscopy, which exploit the moments of the Hamiltonian to calculate relevant thermodynamic properties, determine JFe–Cu = 0.10 cm–1 for 3 and JFe–Ni = 0.025 cm–1 for 4. Q-band electron paramagnetic resonance spectra of 1 reveal a significant...
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- 2018
13. Imposing high-symmetry and tuneable geometry on lanthanide centres with chelating Pt and Pd metalloligands
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Linda H. Doerrer, Morten Gotthold Vinum, Jesper Mortensen, Mikkel Sørensen, Høgni Weihe, and Jesper Bendix
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Lanthanide ,010405 organic chemistry ,Ligand ,Chemistry ,Coordination number ,Inorganic chemistry ,General Chemistry ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,law.invention ,Ion ,Tetragonal crystal system ,Crystallography ,law ,Molecular symmetry ,HSAB theory ,Electron paramagnetic resonance - Abstract
Exploitation of HSAB preferences allows for high-yield, one-pot syntheses of lanthanide complexes chelated by two Pd or Pt metalloligands, [MII(SAc)4]2− (SAc− = thioacetate, M = Pd, Pt). The resulting complexes with 8 oxygen donors surrounding the lanthanides can be isolated in crystallographically tetragonal environments as either [NEt4]+ (space group: P4/mcc) or [PPh4]+ (space group: P4/n) salts. In the case of M = Pt, the complete series of lanthanide complexes has been structurally characterized as the [NEt4]+ salts (except for Ln = Pm), while the [PPh4]+ salts have been structurally characterized for Ln = Gd–Er, Y. For M = Pd, selected lanthanide complexes have been structurally characterized as both salts. The only significant structural difference between salts of the two counter ions is the resulting twist angle connecting tetragonal prismatic and tetragonal anti-prismatic configurations, with the [PPh4]+ salts approaching ideal D4d symmetry very closely (φ = 44.52–44.61°) while the [NEt4]+ salts exhibit intermediate twist angles in the interval φ = 17.28–27.41°, the twist increasing as the complete 4f series is traversed. Static magnetic properties for the latter half of the lanthanide series are found to agree well in the high temperature limit with the expected Curie behavior. Perpendicular and parallel mode EPR spectroscopy on randomly oriented powder samples and single crystals of the Gd complexes with respectively Pd- and Pt-based metalloligands demonstrate the nature of the platinum metal to strongly affect the spectra. Consistent parametrization of all of the EPR spectra reveals the main difference to stem from a large difference in the magnitude of the leading axial term, B02, this being almost four times larger for the Pt-based complexes as compared to the Pd analogues, indicating a direct Pt(5dz2)–Ln interaction and an arguable coordination number of 10 rather than 8. The parametrization of the EPR spectra also confirms that off-diagonal operators are associated with non-zero parameters for the [NEt4]+ salts, while only contributing minimally for the [PPh4]+ salts in which lanthanide coordination approximates D4d point group symmetry closely.
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- 2017
14. Lanthanide coordination complexes framed by sodium ions: slow relaxation of the magnetization in the Dy(III) derivative
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Mikkel Sørensen, Høgni Weihe, Andreas Konstantatos, and Jesper Bendix
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Lanthanide ,Denticity ,010405 organic chemistry ,Chemistry ,Ligand ,Inorganic chemistry ,Relaxation (NMR) ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,Magnetization ,Crystallography ,Molecule ,Single-molecule magnet ,Isostructural - Abstract
Using a new polydentate Schiff-base ligand (H3L) we isolated three new tetranuclear isostructural lanthanide complexes with the general formula [LnNa2(L)4(DMF)4(H2O)2(AcO)2]·4DMF·2H2O [Ln = Dy (1), Ho (2), or Er (3)]. The structural characterization of the complexes reveals that the Na+ ions are coordinated in the structure which gives them a structure-directing role in the molecule. The magnetic behavior of the systems was investigated by means of SQUID magnetometry which revealed that complex 1 exhibits single molecule magnet behavior at low temperatures which is enhanced by the application of a 2000 Oe static magnetic field. We were able to extract an effective barrier of Ueff = 43(1) K, however, we show that the consideration of an Orbach relaxation mechanism being the dominant is not always correct for lanthanides. On the contrary, we elaborate how in this system the relaxation is caused by a combination of a direct and a Raman process.
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- 2017
15. [CrIII8NiII6]n+ Heterometallic Coordination Cubes
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Eric J. L. McInnes, Stergios Piligkos, Høgni Weihe, Euan K. Brechin, Helen M. O'Connor, Mateusz B. Pitak, Sergio Sanz, Nicholas F. Chilton, Aaron J. Scott, Simon J. Coles, Wim T. Klooster, and Paul J. Lusby
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Chromium ,Models, Molecular ,Materials science ,Molecular Conformation ,molecular magnetism ,Supramolecular chemistry ,Pharmaceutical Science ,Article ,supramolecular chemistry ,Spectral line ,Analytical Chemistry ,law.invention ,Ion ,lcsh:QD241-441 ,Paramagnetism ,magnetometry ,lcsh:Organic chemistry ,Coordination Complexes ,Nickel ,law ,TheoryofComputation_ANALYSISOFALGORITHMSANDPROBLEMCOMPLEXITY ,Drug Discovery ,Physical and Theoretical Chemistry ,Electron paramagnetic resonance ,Magnetic Phenomena ,Organic Chemistry ,heterometallic clusters ,Magnetic susceptibility ,Crystallography ,Ferromagnetism ,Chemistry (miscellaneous) ,ddc:540 ,Molecular Medicine ,EPR spectroscopy - Abstract
Three new heterometallic [CrIII8NiII6] coordination cubes of formulae [CrIII8NiII6L24(H2O)12](NO3)12 (1), [CrIII8NiII6L24(MeCN)7(H2O)5](ClO4)12 (2), and [CrIII8NiII6L24Cl12] (3) (where HL = 1-(4-pyridyl)butane-1,3-dione), were synthesised using the paramagnetic metalloligand [CrIIIL3] and the corresponding NiII salt. The magnetic skeleton of each capsule describes a face-centred cube in which the eight CrIII and six NiII ions occupy the eight vertices and six faces of the structure, respectively. Direct current magnetic susceptibility measurements on (1) reveal weak ferromagnetic interactions between the CrIII and NiII ions, with JCr-Ni = + 0.045 cm−1. EPR spectra are consistent with weak exchange, being dominated by the zero-field splitting of the CrIII ions. Excluding wheel-like structures, examples of large heterometallic clusters containing both CrIII and NiII ions are rather rare, and we demonstrate that the use of metalloligands with predictable bonding modes allows for a modular approach to building families of related polymetallic complexes. Compounds (1)–(3) join the previously published, structurally related family of [MIII8MII6] cubes, where MIII = Cr, Fe and MII = Cu, Co, Mn, Pd.
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- 2021
16. Iridates from the molecular side
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Fabrice Wilhelm, Yanhua Lan, Høgni Weihe, Alain Tressaud, Andrei Rogalev, Serghei Ostrovsky, Wolfgang Wernsdorfer, Kasper S. Pedersen, Zaher Salman, Stergios Piligkos, Sophia I. Klokishner, Jesper Bendix, Corine Mathonière, Daniel N. Woodruff, Katharina Ollefs, Etienne Durand, Rodolphe Clérac, Thorbjørn J. Morsing, Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB), Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut Polytechnique de Bordeaux-Université de Bordeaux (UB), Centre de Recherche Paul Pascal (CRPP), Université de Bordeaux (UB)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Department of Chemistry [Copenhagen], Faculty of Science [Copenhagen], University of Copenhagen = Københavns Universitet (KU)-University of Copenhagen = Københavns Universitet (KU), Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute (PSI), Department of Biochemistry, University of Oxford, University of Oxford [Oxford], Circuits électroniques quantiques Alpes (QuantECA ), Institut Néel (NEEL), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Institute of Applied Physics, Academy of Sciences of Moldova, Academy of Sciences of Moldova (ASM), European Synchrotron Radiation Facility (ESRF), ANR-13-BS10-0001,MolQuSpin,Spintronique moléculaire quantique(2013), European Project: GdR MCM-2, Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), University of Copenhagen = Københavns Universitet (UCPH)-University of Copenhagen = Københavns Universitet (UCPH), University of Oxford, and Circuits électroniques quantiques Alpes (NEEL - QuantECA)
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Field (physics) ,Science ,General Physics and Astronomy ,Nanotechnology ,02 engineering and technology ,Electronic structure ,01 natural sciences ,Article ,General Biochemistry, Genetics and Molecular Biology ,Soft chemistry ,Ion ,Crystal ,Paramagnetism ,0103 physical sciences ,010306 general physics ,Quantum ,Physics ,Multidisciplinary ,General Chemistry ,[CHIM.MATE]Chemical Sciences/Material chemistry ,Physik (inkl. Astronomie) ,021001 nanoscience & nanotechnology ,Chemical physics ,0210 nano-technology ,Ground state - Abstract
New exotic phenomena have recently been discovered in oxides of paramagnetic Ir4+ ions, widely known as ‘iridates'. Their remarkable properties originate from concerted effects of the crystal field, magnetic interactions and strong spin-orbit coupling, characteristic of 5d metal ions. Despite numerous experimental reports, the electronic structure of these materials is still challenging to elucidate, and not attainable in the isolated, but chemically inaccessible, [IrO6]8– species (the simplest molecular analogue of the elementary {IrO6}8− fragment present in all iridates). Here, we introduce an alternative approach to circumvent this problem by substituting the oxide ions in [IrO6]8− by isoelectronic fluorides to form the fluorido-iridate: [IrF6]2−. This molecular species has the same electronic ground state as the {IrO6}8− fragment, and thus emerges as an ideal model for iridates. These results may open perspectives for using fluorido-iridates as building-blocks for electronic and magnetic quantum materials synthesized by soft chemistry routes., Iridates are known to exhibit a range of exotic electronic and magnetic behaviours but it is difficult to prepare isolated [IrO6]8− species via soft chemical routes. Here, the authors isolate the isoelectronic [IrF6]2− complex, and assess it as a model and for iridate analogues.
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- 2016
17. Modular [Fe
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Sergio, Sanz, Helen M, O'Connor, Priyanka, Comar, Amgalanbaatar, Baldansuren, Mateusz B, Pitak, Simon J, Coles, Høgni, Weihe, Nicholas F, Chilton, Eric J L, McInnes, Paul J, Lusby, Stergios, Piligkos, and Euan K, Brechin
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The reaction of the simple metalloligand [Fe
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- 2018
18. Magnetic anisotropy switch: Easy axis to easy plane conversion and vice versa
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Philipp P. Hallmen, Kim Lefmann, Ana B. Arauzo, Høgni Weihe, Mauro Perfetti, Elena Bartolomé, Joris van Slageren, Jesper Bendix, Samuel Lenz, Mikkel Sørensen, Heiko Bamberger, Juan Bartolomé, Tom Fennell, U. B. Hansen, Giovanna G. Simeoni, Paul Scherrer Institute (Switzerland), Agencia Estatal de Investigación (España), Danish Agency for Science, Technology and Innovation, German Research Foundation, Oticon Foundation, Augustinus Foundation, University of Stuttgart, Ministerio de Economía y Competitividad (España), European Commission, and Ministerio de Ciencia, Innovación y Universidades (España)
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Materials science ,Library science ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Biomaterials ,Electrochemistry ,media_common.cataloged_instance ,European union ,0210 nano-technology ,Independent research ,media_common - Abstract
The rational design of the magnetic anisotropy of molecular materials constitutes a goal of primary importance in molecular magnetism. Indeed, the applications of molecular nanomagnets, such as single-molecule magnets and molecular magnetic refrigerants, depend on the full control over this property. Axially anisotropic magnetic systems are frequently classified as easy axis or easy plane, depending on whether the lowest energy is obtained by application of a magnetic field parallelly or perpendicularly to the unique axis. Here, the magnetic aniso-tropy of three lanthanide complexes is studied as a function of magnetic field and temperature. It is found that for two of these the type of magnetic aniso-tropy switches as a function of these parameters. Thus, this paper experimen-tally demonstrates that the magnetic anisotropy is not uniquely defined by the intrinsic electronic structure of the systems in question but can also be reversibly switched using external stimuli: temperature and magnetic field., This work is based on experiments performed at the Swiss spallation neutron source SINQ, Paul Scherrer Institute, Villigen, Switzerland. The project was funded by the Independent Research Fund Denmark through the project “Spin Architecture” and the Danish Agency for Science, Technology and Innovation through DANSCATT. M.P., H.B., P.H., S.L., and J.v.S. thank DFG foundation (Project SL 104/5-1). M.A.S. thanks the Oticon Foundation (16-2669) and the Augustinus Foundation (16-2917) for financial support in relation to a research stay at Institut für Physikalische Chemie, Universität Stuttgart, Germany. E.B., A.A., and J. Bartolomé acknowledge the financial support of Spanish MINECO project MAT2017-83468-R. For the experiments conducted at FRM II, this project has received funding from the European Union’s 7th Framework Programme for research, technological development and demonstration under the NMI3-II Grant No. 283883.
- Published
- 2018
19. Chemical tunnel-splitting-engineering in a dysprosium-based molecular nanomagnet
- Author
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Stéphane Rols, Joris van Slageren, Maria Retuerto, U. B. Hansen, Linda H. Doerrer, Henrik M. Rønnow, Juan Bartolomé, Mikkel Sørensen, Elena Bartolomé, Jesper Bendix, Høgni Weihe, Mauro Perfetti, Giovanna G. Simeoni, Hannu Mutka, Ivika Zivkovic, Kim Lefmann, Stergios Piligkos, Kasper S. Pedersen, Minki Jeong, Ana B. Arauzo, Agencia Estatal de Investigación (España), Danish Council for Independent Research, European Commission, Oticon Foundation, University of Stuttgart, German Research Foundation, Danish Research Council, Swiss National Science Foundation, Ministerio de Ciencia, Innovación y Universidades (España), Ministerio de Economía y Competitividad (España), and Augustinus Foundation
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Materials science ,Field (physics) ,Science ,General Physics and Astronomy ,chemistry.chemical_element ,010402 general chemistry ,01 natural sciences ,Article ,General Biochemistry, Genetics and Molecular Biology ,Crystal ,Condensed Matter::Superconductivity ,lcsh:Science ,Quantum tunnelling ,Spin-½ ,Multidisciplinary ,Condensed matter physics ,010405 organic chemistry ,Relaxation (NMR) ,General Chemistry ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Nanomagnet ,0104 chemical sciences ,Tunnell splitting, single molecule magnets, lanthanides, symmetry, spectroscopy ,chemistry ,Dysprosium ,lcsh:Q ,Ground state - Abstract
Total control over the electronic spin relaxation in molecular nanomagnets is the ultimate goal in the design of new molecules with evermore realizable applications in spin-based devices. For single-ion lanthanide systems, with strong spin-orbit coupling, the potential applications are linked to the energetic structure of the crystal field levels and quantum tunneling within the ground state. Structural engineering of the timescale of these tunneling events via appropriate design of crystal fields represents a fundamental challenge for the synthetic chemist, since tunnel splittings are expected to be suppressed by crystal field environments with sufficiently high-order symmetry. Here, we report the long missing study of the effect of a non-linear (C4) to pseudo-linear (D4d) change in crystal field symmetry in an otherwise chemically unaltered dysprosium complex. From a purely experimental study of crystal field levels and electronic spin dynamics at milliKelvin temperatures, we demonstrate the ensuing threefold reduction of the tunnel splitting., M.A.S., U.B.H., K.L., and J.Be. acknowledge financial support from the Danish Research Councils for Independent Research (12-125226). M.A.S., U.B.H., M.R, and K.L. acknowledge DANSCATT for financial support for the neutron scattering experiments. For the experiments conducted at FRM II, this project has received funding from the European Union’s 7th Framework Programme for research, technological development and demonstration under the NMI3-II Grant number 283883. M.A.S. thanks the Oticon Foundation (16-2669), and the Augustinus Foundation (16-2917) for financial support in relation to a research stay at Institut für Physikalische Chemie, Universität Stuttgart, Germany. M.P. and J.v.S. thank the DFG for funding (SL104/5-1). K.S.P. thanks the Danish Research Council for Independent Research for a DFF-Sapere Aude Research Talent grant (4090-00201). E.B., A.A, and, J.Ba. acknowledge the financial support of Spanish MINECO project MAT2017-83468-R. M.J. acknowledges the Swiss National Science Foundation.
- Published
- 2018
20. [ReF6]2−: A Robust Module for the Design of Molecule-Based Magnetic Materials
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Kasper S. Pedersen, Marc Sigrist, Mikkel A. Sørensen, Anne-Laure Barra, Thomas Weyhermüller, Stergios Piligkos, Christian Aa. Thuesen, Morten G. Vinum, Hannu Mutka, Høgni Weihe, Rodolphe Clérac, and Jesper Bendix
- Subjects
General Medicine - Published
- 2014
21. Modifying the properties of 4f single-ion magnets by peripheral ligand functionalisation
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Høgni Weihe, Jan Dreiser, Stéphane Rols, Marc Sigrist, Veacheslav Vieru, Kasper S. Pedersen, Magnus Schau-Magnussen, Hannu Mutka, Liviu F. Chibotaru, Oliver Waldmann, Alexander Sundt, Liviu Ungur, and Jesper Bendix
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Condensed matter physics ,Magnetometer ,Chemistry ,Relaxation (NMR) ,Ab initio ,General Chemistry ,7. Clean energy ,Molecular physics ,Spectral line ,Inelastic neutron scattering ,law.invention ,SQUID ,Magnetization ,law ,Electron paramagnetic resonance - Abstract
We study the ligand-field splittings and magnetic properties of three ErIII single-ion magnets which differ in the peripheral ligand sphere but exhibit similar first coordination spheres by inelastic neutron scattering (INS) and SQUID magnetometry. The INS spectra of the three compounds are profoundly different pointing at a strong response of the magnetic behavior to minor structural changes, as they are e.g. encountered when depositing molecules on surfaces. The observation of several magnetic excitations within the J = 15/2 ground multiplet together with single-crystal magnetic measurements allows for the extraction of the sign and magnitude of all symmetry-allowed Stevens parameters. The parameter values and the energy spectrum derived from INS are compared to the results of state-of-the-art ab initio CASSCF calculations. Temperature-dependent alternating current (ac) susceptibility measurements suggest that the magnetisation relaxation in the investigated temperature range of 1.9 K < T < 5 K is dominated by quantum tunnelling of magnetisation and two-phonon Raman processes. The possibility of observing electron paramagnetic resonance transitions between the ground-state doublet states, which can be suppressed in perfectly axial single-ion magnets, renders the studied systems interesting as representations of quantum bits., Chemical Science, 5 (4), ISSN:2041-6520, ISSN:2041-6539
- Published
- 2014
- Full Text
- View/download PDF
22. Magnetic interactions in oxide-bridged dichromium(III) complexes. Computational determination of the importance of non-bridging ligands
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Høgni Weihe, Anders Døssing, Thorbjørn J. Morsing, Stephan P. A. Sauer, and Jesper Bendix
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Coupling ,Coupling constant ,Bridging (networking) ,Magnetism ,Oxide ,chemistry.chemical_element ,Magnetic susceptibility ,Antiferromagnetic coupling ,Inorganic Chemistry ,chemistry.chemical_compound ,Crystallography ,Chromium ,chemistry ,Computational chemistry ,Materials Chemistry ,Physical and Theoretical Chemistry - Abstract
The magnetic susceptibility of the dinuclear chromium(III) complex[(CH 3 CN) 5 CrOCr(NCCH 3 ) 5 ](BF 4 ) 4 ·2 CH 3 CN has been measured and analyzed. With a fitted value of the triplet energy J = 650 cm −1 , the antiferromagnetic coupling is the strongest hitherto determined for an unsupported linear oxide-bridged dinuclear Cr(III) system. The applicability of DFT for computational prediction of exchange in strongly coupled chromium(III) dimers was examined and an optimal and accurate modeling approach was devised. By such modeling it was shown possible to reproduce experimental exchange coupling constants with small relative errors typically of less than 10% ranging from the strongest coupled systems to systems with moderately strong couplings. A significant influence (>20%) of the chemical nature of the peripheral, non-bridging ligands on the exchange coupling was found and rationalized.
- Published
- 2013
23. In-Depth Magnetic Characterization of a [2 × 2] Mn(III) Square Grid Using SQUID Magnetometry, Inelastic Neutron Scattering, and High-Field Electron Paramagnetic Resonance Spectroscopy
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Robert Bewley, Stergios Piligkos, Andreas Konstantatos, Høgni Weihe, Anne-Laure Barra, and Jesper Bendix
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Condensed matter physics ,010405 organic chemistry ,Magnetometer ,Chemistry ,chemistry.chemical_element ,Manganese ,010402 general chemistry ,01 natural sciences ,Molecular physics ,Inelastic neutron scattering ,0104 chemical sciences ,law.invention ,Characterization (materials science) ,Inorganic Chemistry ,SQUID ,Condensed Matter::Materials Science ,Magnetization ,law ,Physical and Theoretical Chemistry ,Electron paramagnetic resonance ,Anisotropy - Abstract
A tetranuclear [2 × 2] grid-like manganese(III) Schiff base complex, Mn4, has been synthesized and characterized by single-crystal X-ray crystallography. Direct-current magnetization measurements were performed on the system and proved to be insufficient for an accurate magnetic model to be deduced. Combined inelastic neutron scattering (INS) and electron paramagnetic resonance (EPR) experiments provided the necessary information in order to successfully model the magnetic properties of Mn4. The resulting model takes into account both the magnitude and the relative orientations of the single-ion anisotropy tensors.
- Published
- 2016
24. Toward Molecular 4f Single-Ion Magnet Qubits
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Kasper S. Pedersen, Simon G. McAdams, Jesper Bendix, Floriana Tuna, Stergios Piligkos, Høgni Weihe, Ana-Maria Ariciu, Centre de recherches Paul Pascal (CRPP), Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB), Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut Polytechnique de Bordeaux-Université de Bordeaux (UB), School of Chemistry and Photon Science Institute, University of Manchester [Manchester], Department of Chemistry [Copenhagen], Faculty of Science [Copenhagen], University of Copenhagen = Københavns Universitet (KU)-University of Copenhagen = Københavns Universitet (KU), and The Danish Council for Independent Research for a DFF Sapere Aude: Research Talent grant (4090-00201), research grant 12-125226, and a Sapere Aude DFF-Starting Grant (10-081659).
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Physics ,Rabi cycle ,Pulsed EPR ,[CHIM.MATE]Chemical Sciences/Material chemistry ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Colloid and Surface Chemistry ,Magnet ,Qubit ,Spin echo ,Atomic physics ,0210 nano-technology ,Spectroscopy ,Single crystal ,Quantum - Abstract
International audience; Quantum coherence is detected in the 4f single-ion magnet (SIM) Yb(trensal), by isotope selective pulsed EPR spectroscopy on an oriented single crystal. At X-band, the spin-lattice relaxation (T1) and phase memory (Tm) times are found to be independent of the nuclei bearing, or not, a nuclear spin. The observation of Rabi oscillations of the spin echo demonstrates the possibility to coherently manipulate the system for more than 70 rotations. This renders Yb(trensal), a sublimable and chemically modifiable SIM, an excellent candidate for quantum information processing.
- Published
- 2016
25. Probing Effective Hamiltonian Operators by Single-Crystal EPR: A Case Study Using Dinuclear Cr(III) Complexes
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Høgni Weihe, Jesper Bendix, and Thorbjørn J. Morsing
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chemistry.chemical_classification ,010405 organic chemistry ,Magnetism ,Chemistry ,Exchange interaction ,chemistry.chemical_element ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,law.invention ,Coordination complex ,Inorganic Chemistry ,symbols.namesake ,Chromium ,Computational chemistry ,law ,symbols ,Statistical physics ,Physical and Theoretical Chemistry ,Anisotropy ,Hamiltonian (quantum mechanics) ,Electron paramagnetic resonance ,Single crystal - Abstract
The use of a simple two-center model to describe exchange-coupled systems of various complexities is common in the field of coordination chemistry and molecular magnetism. In this work we investigate the applicability of this model experimentally, employing multifrequency, single-crystal EPR on axial dinuclear chromium(III) systems amenable to accurate parametrizations. The very high confidence with which zero-field splitting parameters can be determined by this technique, applied to the systems in question, allows for an in-depth analysis of the modeling. We experimentally demonstrate and qualitatively account for the energy-dependent modification of the spin-multiplet anisotropies, which is introduced by the exchange interaction. Even for the simple systems under consideration, we find that the standard modeling provides an inadequate parametrization of experimental data, and we present a convenient model extension, which improves the description.
- Published
- 2016
26. MnIII zero-field splitting parameters and weak exchange interactions in a cyanide-bridged {MnIII–IrIII–MnIII} cluster
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Anne-Laure Barra, Philip L. W. Tregenna-Piggott, Marc Sigrist, Jan Dreiser, Kasper S. Pedersen, Magnus Schau-Magnussen, Høgni Weihe, Hannu Mutka, and Jesper Bendix
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Condensed matter physics ,010405 organic chemistry ,Chemistry ,Exchange interaction ,Zero field splitting ,010402 general chemistry ,01 natural sciences ,Inelastic neutron scattering ,0104 chemical sciences ,law.invention ,Inorganic Chemistry ,Crystallography ,law ,Materials Chemistry ,Cluster (physics) ,Diamagnetism ,Antiferromagnetism ,Physical and Theoretical Chemistry ,Isostructural ,Electron paramagnetic resonance - Abstract
The reaction of [MnIII(5-Brsalen)(MeOH)](ClO4) (5-Brsalen2 − = N,N′-ethylenebis(5-bromosalicylidene-iminate)) with [IrIII(CN)6]3 − yields a trinuclear, cyanide-bridged MnIII–IrIII–MnIII cluster which is a member of an isostructural series of MnIII–MIII–MnIII clusters. The presence of the large, diamagnetic [IrIII(CN)6]3 − bridging unit facilitates a precise determination of the MnIII zero-field splitting (zfs) parameters by the combined use of inelastic neutron scattering, high-field, high-frequency EPR spectroscopy and magnetic measurements. The single-ion axial (D) and rhombic (E) zfs parameters are found to be D = − 3.72(5) cm− 1 and |E| = 0.21(1) cm− 1. The experimental data are consistent with a small, antiferromagnetic exchange interaction between the two MnIII ions.
- Published
- 2012
27. An oxide-bridged Dy–ReV–Dy single-molecule magnet
- Author
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Christian Aa. Thuesen, Jesper Bendix, Høgni Weihe, Kasper S. Pedersen, Magnus Schau-Magnussen, and Jan Dreiser
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Lanthanide ,Stereochemistry ,Exchange interaction ,chemistry.chemical_element ,Rhenium ,Inorganic Chemistry ,Chromium ,Crystallography ,chemistry ,Materials Chemistry ,Diamagnetism ,Single-molecule magnet ,Physical and Theoretical Chemistry ,Isostructural ,Solid solution - Abstract
The reaction of diamagnetic trans-[ReV(O)2(py)4]NO3 with [Ln(hfac)3(H2O)2] (Ln = Dy, Y, Tb; hfac− = 1,1,1,5,5,5-hexafluoroacetylacetonate(1–)) in chloroform yields oxide-bridged, trinuclear [Ln(hfac)3(H2O)–Re(O)2(py)4–Ln(hfac)3(NO3)] (DyReDy, YReY, TbReTb). The series is isostructural to a fluoride-bridged {Dy–Cr–Dy} complex previously reported (Dreiser et al., Chem. Sci. 3 (2012) 1024) but, notably, DyReDy exhibits frequency-dependent out-of-phase ac susceptibility (χ″) signals at higher temperatures than the chromium analogue. Magnetic investigations of a solid solution of Dy3+ in YReY reveal the presence of a small Dy–Dy exchange interaction in DyReDy.
- Published
- 2012
28. Direct observation of a ferri-to-ferromagnetic transition in a fluoride-bridged 3d–4f molecular cluster
- Author
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Stergios Piligkos, Peter M. Oppeneer, Frithjof Nolting, Stefano Rusponi, Jesper Bendix, Magnus Schau-Magnussen, Zaher Salman, Oliver Waldmann, Christian Aa. Thuesen, Høgni Weihe, Md. Ehesan Ali, Kasper S. Pedersen, Hannu Mutka, Cinthia Piamonteze, Harald Brune, and Jan Dreiser
- Subjects
Crystal-Structure ,Exchange Coupling-Constants ,Magnetic moment ,Condensed matter physics ,Magnetic circular dichroism ,Chemistry ,Chromium(Iii) Complexes ,Wave Method ,General Chemistry ,High-Spin ,Dichromium(Iii) Complex ,Nanomagnet ,Substituted Tetrahydrosalen Derivatives ,Anisotropy Barrier ,Magnetization ,Crystallography ,Ferromagnetism ,Ferrimagnetism ,Superexchange ,Antiferromagnetism ,Metal-Complexes ,Magnetic Circular-Dichroism - Abstract
We report on the synthesis, crystal structure and magnetic characterisation of the trinuclear, fluoride-bridged, molecular nanomagnet [Dy(hfac)(3)(H2O)-CrF2(py)(4)-Dy(hfac)(3)(NO3)] (1) (hfacH = 1,1,1,5,5,5-hexafluoroacetylacetone, py = pyridine) and a closely related dinuclear species [Dy(hfac)(4)-CrF2( py)(4)]center dot 1/2 CHCl3 (2). Element-specific magnetisation curves obtained on 1 by X-ray magnetic circular dichroism (XMCD) allow us to directly observe the field-induced transition from a ferrimagnetic to a ferromagnetic arrangement of the Dy and Cr magnetic moments. By fitting a spin-Hamiltonian model to the XMCD data we extract a weak antiferromagnetic exchange coupling of j -0.18 cm(-1) between the Dy-III and Cr-III ions. The value found from XMCD is consistent with SQUID magnetometry and inelastic neutron scattering measurements. Furthermore, alternating current susceptibility and muon-spin relaxation measurements reveal that 1 shows thermally activated relaxation of magnetisation with a small effective barrier for magnetisation reversal of Delta(eff) 3 cm(-1). Density-functional theory calculations show that the Dy-Cr couplings originate from superexchange via the fluoride bridges.
- Published
- 2012
29. Crystal structure of tri-hydrogen bis-{[1,1,1-tris-(2-oxido-ethyl-amino-meth-yl)ethane]-cobalt(III)} trinitrate
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Stergios Piligkos, Høgni Weihe, Thorbjørn J. Morsing, Heini V. Johannesen, and Waqas Sethi
- Subjects
Tris ,crystal structure ,Hydrogen ,Stereochemistry ,Dimer ,racemic conglomerate ,chemistry.chemical_element ,Crystal structure ,1,1,1-tris(2-hydroxyethylaminomethybethane ,Crystal ,chemistry.chemical_compound ,1,1,1-tris(2-hydroxyethylaminomethyl)ethane ,General Materials Science ,Crystallography ,Chemistry ,Hydrogen bond ,General Chemistry ,Meth ,1,1,1-tris(2-hydroxyethylaminomethyl)ethane ,Condensed Matter Physics ,Data Reports ,cobalt(III) complex ,QD901-999 ,hydrogen-bonding motif ,Cobalt - Abstract
The title compound, [Co2(L)2]3+·3NO3−[whereL= CH3C(CH2NHCH2CH2OH1/2)3], has been synthesized from the ligand 1,1,1-tris(2-hydroxyethylaminomethyl)ethane. The cobalt(III) dimer has an interesting and uncommon O—H...O hydrogen-bonding motif with the three bridging hydroxy H atoms each being equally disordered over two positions. In the dimeric trication, the octahedrally coordinated CoIIIatoms and the capping C atoms lie on a threefold rotation axis. The N atoms of two crystallographically independent nitrate anions also lie on threefold rotation axes. N—H...O hydrogen bonding between the complex cations and nitrate anions leads to the formation of a three-dimensional network structure. The compound is a racemic conglomerate of crystals containing either D or L molecules. The crystal used for this study is a D crystal.
- Published
- 2015
30. Frequency-Domain Fourier-Transform Terahertz Spectroscopy of the Single-Molecule Magnet (NEt4)[Mn2(5-Brsalen)2(MeOH)2Cr(CN)6]
- Author
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Kasper S. Pedersen, Alexander Schnegg, Oliver Waldmann, Magnus Schau-Magnussen, Jesper Bendix, Høgni Weihe, Hannu Mutka, Philip L. W. Tregenna-Piggott, Joscha Nehrkorn, Jan Dreiser, and Karsten Holldack
- Subjects
Chemistry ,Phonon ,Terahertz radiation ,Organic Chemistry ,Analytical chemistry ,General Chemistry ,Magnetic susceptibility ,Catalysis ,Inelastic neutron scattering ,law.invention ,Terahertz spectroscopy and technology ,Magnetization ,law ,Single-molecule magnet ,Electron paramagnetic resonance - Abstract
We have investigated the novel single-molecule magnet (NEt(4))[Mn(2)(5-Brsalen)(2)(MeOH)(2)Cr(CN)(6)] (1; 5-Brsalen = N,N'-ethylenebis(5-bromosalicylidene)iminato anion) using spectroscopic as well as magnetization and susceptibility measurements. Frequency-domain Fourier-transform terahertz electron paramagnetic resonance (FDFT THz-EPR) based on the generation of THz radiation from a synchrotron in combination with inelastic neutron scattering (INS) allows for the discrimination between intermultiplet and intramultiplet transitions. Together with ac/dc magnetic susceptibility measurements the obtained set of data provides a complete characterization of the lowest energetic magnetic excitations. We find that the new compound 1 exhibits much weaker intermolecular interactions than found in the closely related compound: K[Mn(2)(5-Brsalen)(2)(H(2)O)(2)Cr(CN)(6)] (2). Furthermore, two phonon lines in the vicinity of the magnetic excitations are detected.
- Published
- 2011
31. Enhancing the Blocking Temperature in Single-Molecule Magnets by Incorporating 3d-5d Exchange Interactions
- Author
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Magnus Schau-Magnussen, Hannu Mutka, Jesper Bendix, Philip L. W. Tregenna-Piggott, Høgni Weihe, Kasper S. Pedersen, Andrei V. Palii, Sophia I. Klokishner, Serghei Ostrovsky, and Oleg S. Reu
- Subjects
Arrhenius equation ,010405 organic chemistry ,Stereochemistry ,Organic Chemistry ,Exchange interaction ,chemistry.chemical_element ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Magnetic susceptibility ,Catalysis ,0104 chemical sciences ,Ion ,symbols.namesake ,Crystallography ,Ferromagnetism ,chemistry ,symbols ,Molecule ,Osmium ,Isostructural - Abstract
We report the first single-molecule magnet (SMM) to incorporate the [Os(CN)(6)](3-) moiety. The compound (1) has a trimeric, cyanide-bridged Mn(III)-Os(III)-Mn(III) skeleton in which Mn(III) designates a [Mn(5-Brsalen)(MeOH)](+) unit (5-Brsalen=N,N'-ethylenebis(5-bromosalicylideneiminato)). X-ray crystallographic experiments reveal that 1 is isostructural with the Mn(III)-Fe(III)-Mn(III) analogue (2). Both compounds exhibit a frequency-dependent out-of-phase χ''(T) alternating current (ac) susceptibility signal that is suggestive of SMM behaviour. From the Arrhenius expression, the effective barrier for 1 is found to be Δ(eff)/k(B)=19 K (τ(0)=5.0×10(-7) s; k(B)=Boltzmann constant), whereas only the onset (1.5 kHz, 1.8 K) of χ''(T) is observed for 2, thus indicating a higher blocking temperature for 1. The strong spin-orbit coupling present in Os(III) isolates the E'(1g(1/2))(O(h)*) Kramers doublet that exhibits orbital contributions to the single-ion anisotropy. Magnetic susceptibility and inelastic neutron-scattering measurements reveal that substitution of [Fe(CN)(6)](3-) by the [Os(CN)(6)](3-) anion results in larger ferromagnetic, anisotropic exchange interactions going from quasi-Ising exchange interactions in 2 to pure Ising exchange for 1 with J(parallel)(MnOs)=-30.6 cm(-1). The combination of diffuse magnetic orbitals and the Ising-type exchange interaction effectively contributes to a higher blocking temperature. This result is in accordance with theoretical predictions and paves the way for the design of a new generation of SMMs with enhanced SMM properties.
- Published
- 2010
32. Alkali metal cation complexation and solvent interactions by robust chromium(III) fluoride complexes
- Author
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Torben Birk, Høgni Weihe, Stergios Piligkos, Jesper Bendix, Anders Holten, and Magnus Magnussen
- Subjects
Sodium ,Organic Chemistry ,Inorganic chemistry ,chemistry.chemical_element ,Alkali metal ,Biochemistry ,Sodium salt ,Ion ,Inorganic Chemistry ,Solvent ,Chromium ,chemistry.chemical_compound ,Crystallography ,chemistry ,Environmental Chemistry ,Hypsochromic shift ,Physical and Theoretical Chemistry ,Fluoride - Abstract
Interaction of robust chromium(III) fluoride complexes with sodium or lithium cations in solution lead to hypsochromic spectral shifts of increasing magnitude along the series: trans-[CrF2(py)4]+, mer-[CrF3(terpy)], and fac-[CrF3(Me3tacn)]. Crystalline products isolated from solution exhibit μ2-bridging by the fluoride ligands in a linear fashion between Na+-ions and chromium centres in catena-[Na(H2O)4(μ-F)-trans-{CrF(py)4}](HCO3)2 and in the dimers [Li(H2O)n(μ-F)-trans-{CrF(py)4}]2+ (n = 3, 4). The uncharged chromium complexes fac-[CrF3(Me3tacn)] and mer-[CrF3(terpy)] have been synthesized from mer-[CrF3(py)3] and shown to precipitate sodium salts from solution, of which 3[CrF3(Me3tacn)]·2Na(Bph4)·solv and 6[CrF3(terpy)]·4Na(Bph4)·solv have been crystallographically characterized. In these clusters, the neutral fluoride complexes bring the Na+ cation separation down to 3.610 A and 3.369 A, respectively, which is much closer than the inter-cation distance in NaCl and comparable to that of NaF. DFT calculations support the notion of a strong interaction between Na+ ions and neutral chromium(III) fluoride complexes. The calculations reproduce the magnitude and the counter-intuitive sign of the spectral shifts induced by second sphere complexation in solution, which originates in a breakdown of the assumption of parameter transferability in ligand-field descriptions.
- Published
- 2010
33. The First Coordination Compound with 5-methylisoxazole-3-carboxylate: Synthesis and Structural Characterization of [Cu(L2)(H2O)] · H2O
- Author
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Høgni Weihe and Torben Birk
- Subjects
chemistry.chemical_classification ,Denticity ,Chemistry ,Ligand ,Carboxylic acid ,General Chemistry ,Crystal structure ,Triclinic crystal system ,Condensed Matter Physics ,Coordination complex ,chemistry.chemical_compound ,Crystallography ,Pyridine ,Carboxylate - Abstract
The title compound, aquabis(5-methylisoazole-3-carboxylato-O,N)copper(II) monohydrate, [Cu(L2)(H2O)] · H2O is synthesized and characterized by X-ray diffraction, elementary analysis, and IR. The ligand coordinates to the copper center in a bidentate O,N fashion through the carboxylic acid moiety and the heteroaromatic nitrogen atom. The complex crystallizes in the triclinic space group $${\bar{P}} 1$$ with unit cell parameters a = 8.4080(12)A, b = 8.810(3), c = 10.318(2)A, α = 110.08(3)°, β = 104.81(2)°, γ = 103.149(16)°, V = 650.9(3)A3, Z = 2. In addition, the synthesis of the free acid 5-methylisoazole-3-carboxylic acid and pyridine containing complex bis(5-methylisoazole-3-carboxylato)bispyridinecopper(II) monohydrate is described. Synthesis and crystal structure of aquabis(5-methylisoazole-3-carboxylato-O,N)copper(II)monohydrate. The first coordination compound of 5-methylisoxazole-3-carboxylic acid.
- Published
- 2009
34. EPR OF Mn2+IMPURITIES IN CALCITE: A DETAILED STUDY PERTINENT TO MARBLE PROVENANCE DETERMINATION
- Author
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I. Laursen, O. Johnsen, Høgni Weihe, Anne-Laure Barra, and Stergios Piligkos
- Subjects
Calcite ,Archeology ,History ,Provenance ,Condensed matter physics ,Mineralogy ,Spin hamiltonian ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Spectral line ,0104 chemical sciences ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Impurity ,Condensed Matter::Strongly Correlated Electrons ,0210 nano-technology ,Electron paramagnetic resonance ,Anisotropy ,Quantum ,Geology - Abstract
We demonstrate that the electron paramagnetic resonance spectrum of Mn2+ impurities in calcite, and therefore also in marble, may be accurately reproduced by a traditional spin Hamiltonian formalism. The success of such a treatment, however, very much depends on the spin Hamiltonian parameters having the correct signs as well as magnitudes. We present data that determine the sign of the axial anisotropy parameter and thereby facilitate future quantum mechanical characterizations of marble electron paramagnetic resonance spectra that supplement provenance determination.
- Published
- 2009
35. Single-Ion Anisotropy and Exchange Interactions in the Cyano-Bridged Trimers MnIII2MIII(CN)6 (MIII = Co, Cr, Fe) Species Incorporating [Mn(5-Brsalen)]+ Units: An Inelastic Neutron Scattering and Magnetic Susceptibility Study
- Author
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Lukas Keller, Denis Sheptyakov, Kasper S. Pedersen, Theis Brock-Nannestad, Philip L. W. Tregenna-Piggott, Oleg S. Reu, Jesper Bendix, Sergei M. Ostrovsky, Hannu Mutka, Høgni Weihe, Sophia I. Klokishner, and Andrei V. Palii
- Subjects
Inorganic Chemistry ,Crystallography ,Range (particle radiation) ,chemistry ,Energy level ,chemistry.chemical_element ,Antiferromagnetism ,Manganese ,Physical and Theoretical Chemistry ,Anisotropy ,Magnetic susceptibility ,MN 5 ,Inelastic neutron scattering - Abstract
The electronic structures of the compounds K[(5-Brsalen)2(H2O)2-Mn2MIII(CN)6]·2H2O (MIII = CoIII, CrIII, FeIII) have been determined by inelastic neutron scattering (INS) and magnetic susceptibility studies, revealing the manganese(III) single-ion anisotropy and exchange interactions that define the low-lying states of the Mn−MIII−Mn trimeric units. Despite the presence of an antiferromagnetic intertrimer interaction, the experimental evidence supports the classification of both the Cr(III) and Fe(III) compounds as single-molecule magnets. The value of 17(2) cm−1 established from AC susceptibility measurements for a spin-reversal barrier of K[(5-Brsalen)2(H2O)2-Mn2Cr(CN)6]·2H2O may be readily rationalized in terms of the energy level diagram determined directly by INS. AC susceptibility measurements on samples of K[(5-Brsalen)2(H2O)2-Mn2Fe(CN)6]·2H2O are contrary to those previously reported, exhibiting but the onset of peaks below temperatures of 1.8 K at oscillating frequencies in the range of 100−800 H...
- Published
- 2008
36. Sign and magnitude of spin Hamiltonian parameters for Mn2+ impurities in calcite. A multi- and low-frequency EPR study
- Author
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I. Laursen, Stergios Piligkos, Høgni Weihe, and Axel Morgenstjerne
- Subjects
Calcite ,Condensed matter physics ,Chemistry ,Biophysics ,Spin hamiltonian ,Low frequency ,Zero field splitting ,Condensed Matter Physics ,Molecular physics ,Spectral line ,law.invention ,chemistry.chemical_compound ,law ,Impurity ,Lattice (order) ,Physical and Theoretical Chemistry ,Electron paramagnetic resonance ,Molecular Biology - Abstract
L-, S-, and X-band powder EPR spectra and an L-band single-crystal spectrum of Mn2+ impurities in calcite were analysed by the fitting of full spectral traces to a theoretical model. This analysis gives as parameters the traditional spin Hamiltonian parameters reflecting the three-fold symmetry of the cation lattice site as well as parameters determining the band shape and width of the resonances. The three frequencies give a consistent description of the system. For this spin system it is shown that the relative sign of the axial zero-field splitting parameter Dand the hyperfine coupling constant A may be safely determined at the L-band.
- Published
- 2007
37. Design of Single-Molecule Magnets: Insufficiency of the Anisotropy Barrier as the Sole Criterion
- Author
-
Heini V. Johannesen, Marc Sigrist, Høgni Weihe, Stéphane Rols, Mikkel Sørensen, Jesper Bendix, Jan Dreiser, Romain Sibille, Kasper S. Pedersen, Hannu Mutka, Stergios Piligkos, Bjarne E. Nielsen, Centre de recherches Paul Pascal (CRPP), Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Department of Chemistry [Copenhagen], Faculty of Science [Copenhagen], University of Copenhagen = Københavns Universitet (KU)-University of Copenhagen = Københavns Universitet (KU), Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB), Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut Polytechnique de Bordeaux-Université de Bordeaux (UB), The Swiss Light Source (SLS) (SLS-PSI), Paul Scherrer Institute (PSI), Institute of Condensed Matter Physics [Lausanne], Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratory for Developments and Methods, PSI, Institut Laue-Langevin (ILL), and ILL
- Subjects
Ligand field theory ,Condensed matter physics ,Magnetic moment ,010405 organic chemistry ,Chemistry ,[CHIM.MATE]Chemical Sciences/Material chemistry ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,symbols.namesake ,Paramagnetism ,Nuclear magnetic resonance ,Excited state ,symbols ,Relaxation (physics) ,Physical and Theoretical Chemistry ,Anisotropy ,Realization (systems) ,Debye model - Abstract
Determination of the electronic energy spectrum of a trigonalsymtnetry mononuclear Yb3+ single-molecule magnet (SMM) by highresolution absorption and luniinescente spectroscopies reveals that the first excited electronic doublet is placed nearly 500 cm(-1) above the ground one. Fitting of the paramagnetic relaxation times of this- SMM to a thermally activated (Orbach) model {tau = tau(0) X exp [Delta(Orbach)/(k(B)T)]} affords an activation barrier, Delta(Orbach), of only 38 cm(-1). This result is incompatible with the spectroscopic observations. Thus, we unambiguously demonstrate, solely on the basis Of experimental data, that Orbach relaxation cannot ci priori be considered as the main mechanism determining the spin dynamics of SM.Ms. This study highlights the fact that the general:synthetic approach of optimizing SMM behavior by maximization of the anisotropy barrier, intimately linked to the ligand field, 'as the sole paratneter to be tuned, is insufficient because of the complete neglect of the interaction of the magnetic moment of the molecule with its environment. The Orbach mechanism is expected dominant only in the cases in which the energy of the excited ligand field state is below the Debye temperature, which is typically low for molecular crystals and, thus, prevents the use of the anisotropy barrier as a design criterion, for the realization of high-temperature SM.Ms. Therefcire, consideration of additional design criteria that address the presence of alternative relaxation processes beyond the traditional double-well picture is required.
- Published
- 2015
38. Facile interchange of 3d and 4f ions in single-molecule magnets: stepwise assembly of [Mn4 ], [Mn3Ln] and [Mn2Ln2 ] cages within calix[4]arene scaffolds
- Author
-
Simon J. Teat, Ross McLellan, Scott J. Dalgarno, Høgni Weihe, Stergios Piligkos, Maria A. Palacios, Euan K. Brechin, and Christine M. Beavers
- Subjects
chemistry.chemical_classification ,Magnetism ,Stereochemistry ,Organic Chemistry ,Relaxation (NMR) ,General Chemistry ,Catalysis ,Coordination complex ,Magnetization ,Crystallography ,chemistry ,Transition metal ,Intramolecular force ,Calixarene ,Molecule - Abstract
The central Mn(II) ions in a series of calix[4]arene-stabilised butterflies can be sequentially replaced with Ln(III) ions, maintaining the structural integrity of the molecule but transforming its magnetic properties. The replacement of Mn(II) for Gd(III) allows for the examination of the transferability of spin-Hamiltonian parameters within the family as well as permitting their reliable determination. The introduction of the 4f ions results in weaker intramolecular magnetic exchange, an increase in the number of low-lying excited states, and an increase in magnetisation relaxation, highlighting the importance of exchange over single-ion anisotropy for the observation of SMM behaviour in this family of complexes. The presence of the [TM(II/III) (TBC[4])(OH)(solvent)] metalloligand (TM=transition metal, TBC=p-tBu-calix[4]arene) suggests that magnetic calix[n]arene building blocks can be employed to encapsulate a range of different "guests" within structurally robust "hosts".
- Published
- 2015
39. Redox Chemistry of a Dimanganese(II,III) Complex with an Unsymmetric Ligand: Water Binding, Deprotonation and Accumulative Light‐Induced Oxidation
- Author
-
Reiner Lomoth, Stenbjörn Styring, Høgni Weihe, Lars Eriksson, Ann Magnuson, Joakim Högblom, Ping Huang, Magnus F. Anderlund, Björn Åkermark, and Wei Shi
- Subjects
Ligand ,chemistry.chemical_element ,Infrared spectroscopy ,Bioinorganic chemistry ,Manganese ,Photochemistry ,Redox ,law.invention ,Inorganic Chemistry ,Deprotonation ,chemistry ,law ,Polymer chemistry ,Water binding ,Electron paramagnetic resonance - Abstract
A dinuclear manganese complex {[(Mn2L)-L-II,IIII(mu-OAc)(2)]-ClO4} has been synthesised, where L is the dianion of 2-{[bis-(pyrid-2-ylmethyl)amino]methyl}-6-{[(3,5-di-tert-butyl-2- hydroxybenzyl)(p ...
- Published
- 2006
40. Synthesis, Characterisation and Modelling of a Ferromagnetically Coupled Chromium(III) Dimer: Di‐μ‐hydroxobis[tetrakis(isothiocyanato)chromate(III)] (Eur. J. Inorg. Chem. 35/2014)
- Author
-
Thorbjørn J. Morsing, Jesper Bendix, and Høgni Weihe
- Subjects
Inorganic Chemistry ,Chromium ,chemistry.chemical_compound ,Chromate conversion coating ,chemistry ,law ,Dimer ,Inorganic chemistry ,Polymer chemistry ,chemistry.chemical_element ,Electron paramagnetic resonance ,law.invention - Published
- 2014
41. Anisotropic Hyperfine Interaction in the Manganese(III) Hexaaqua Ion
- Author
-
Søren Kegnaes Klitgaard, Itana Krivokapic, Philip L. W. Tregenna-Piggott, Christopher J. Noble, Høgni Weihe, and Anne-Laure Barra
- Subjects
Ions ,Manganese ,Crystallography ,Doping ,Electron Spin Resonance Spectroscopy ,Water ,chemistry.chemical_element ,Spin hamiltonian ,General Medicine ,General Chemistry ,Catalysis ,law.invention ,Ion ,Nuclear magnetic resonance ,chemistry ,law ,Anisotropy ,Condensed Matter::Strongly Correlated Electrons ,Electronic spin ,Atomic physics ,Electron paramagnetic resonance ,Hyperfine structure - Abstract
Caught in the act: Until now, the spatial property of the hyperfine interaction between the S=2 electronic spin and the I=5/2 nuclear spin in any chemically relevant MnIII compound has escaped observation. By taking multifrequency electron paramagnetic resonance measurements (see graph) on the [Mn(OH2)6]3+ ion doped into Cs[Ga(OH2)6](SO4)6 H2O, ground-state spin Hamiltonian parameters have been determined at an unprecedented level of precision.
- Published
- 2005
42. Manganese (III) cyclam complexes with aqua, iodo, nitrito, perchlorato and acetic acid/acetato axial ligands
- Author
-
Henning Osholm Sørensen, Høgni Weihe, Susanne Mossin, Jørgen Glerup, and Inger Søtofte
- Subjects
Magnetism ,Stereochemistry ,Hydrogen bond ,Intermolecular force ,chemistry.chemical_element ,Manganese ,Inorganic Chemistry ,Crystallography ,Acetic acid ,chemistry.chemical_compound ,Tetragonal crystal system ,chemistry ,Octahedron ,Cyclam ,Materials Chemistry ,Physical and Theoretical Chemistry - Abstract
The syntheses, structures and magnetic properties of five new manganese (III) cyclam complexes, trans-[Mn(cyclam)(OH2)2](CF3SO3)3 AE H2O, trans-[Mn(cyclam)I2]I, trans-[Mn(cyclam)(ONO)2]ClO4, trans-[Mn(cyclam)(OClO3)2]ClO4 and trans-[Mn(cyclam) (CH3COO)(CH3COOH)](ClO4)2, are reported. Cyclam is the tetradentate amine ligand 1,4,8,11-tetraazacyclotetradecane. The complexes all exhibit pronounced tetragonal elongation of the coordination octahedron with the four cyclam nitrogens occupying the four equatorial positions. The magnetic properties are consistent with the formulation of the complexes as high-spin d 4 systems. trans-[Mn(cyclam)(OH2)2](CF3SO3)3 AE H2O is shown to be a convenient starting material for the syntheses of trans cyclam complexes. [Mn(cyclam)(CH3COO)(CH3COOH)](ClO4)2 exhibits extremely short intermolecular hydrogen bonds resulting in a pseudo-chain structure. The tilt of the axial ligands with respect to the equatorial plane containing the manganese and the cyclam nitrogen atoms is discussed. � 2004 Elsevier B.V. All rights reserved.
- Published
- 2005
43. High-Field, Multifrequency EPR Study of the [Mn(OH2)6]3+ Cation: Influence of π-Bonding on the Ground State Zero-Field-Splitting Parameters
- Author
-
Anne-Laure Barra, Høgni Weihe, and Philip L. W. Tregenna-Piggott
- Subjects
Ligand field theory ,Absorption spectroscopy ,Condensed matter physics ,chemistry.chemical_element ,Manganese ,Zero field splitting ,Molecular physics ,Symmetry (physics) ,law.invention ,Inorganic Chemistry ,chemistry ,law ,Physical and Theoretical Chemistry ,Anisotropy ,Ground state ,Electron paramagnetic resonance - Abstract
High-field, multifrequency EPR data are presented for the alum CsMn(SO4)2·12D2O, containing the [Mn(OD2)6]3+ cation. The data are interpreted using the conventional S = 2 spin Hamiltonian, and the following parameters determined for the data obtained below 30 K: D = −4.491(7) cm-1, E = 0.248(5) cm-1, gx = 1.981(5), gy = 1.993(5), gz = 1.988(5). Although the deviation of the MnO6 framework from idealized D4h symmetry is small, the magnitude of E/D is significant. The E parameter is related to ligand field parameters derived from the optical absorption spectrum. The rhombic anisotropy is shown to arise as a consequence of the π-anisotropic nature of the manganese(III)−water interaction.
- Published
- 2003
44. Variable temperature inelastic neutron scattering study of chromium(II) Tutton salt: manifestation of the 5E⊗e Jahn–Teller effect
- Author
-
Susanne Mossin, Stefan Janssen, Christopher Dobe, Høgni Weihe, Philip L. W. Tregenna-Piggott, and Hanspeter Andres
- Subjects
Bond length ,Nuclear magnetic resonance ,Chemistry ,Jahn–Teller effect ,General Physics and Astronomy ,Physical chemistry ,Electronic structure ,Physical and Theoretical Chemistry ,Zero field splitting ,Inelastic scattering ,Isostructural ,Atmospheric temperature range ,Inelastic neutron scattering - Abstract
Inelastic neutron scattering (INS) data are presented for the salt (ND 4 ) 2 Cr(OD 2 ) 6 (SO 4 ) 2 , which enable the zero-field-splitting of the 5 A g ( C i ) ground term of the [Cr(OD 2 ) 6 ] 2+ cation to be defined in the temperature range 1.5–297 K. Above ∼100 K, the energies of the INS transitions are strongly temperature-dependent, as are the documented Cr–O bond lengths. The experimental data are interpreted using a 5 E⊗e Jahn–Teller Hamiltonian perturbed by low symmetry strain. Good agreement is obtained using a parameter set analogous to that employed to describe the electronic and molecular structure of the [Cu(OD 2 ) 6 ] 2+ cation in the isostructural copper(II) salt.
- Published
- 2002
45. Competing Interactions in the Tetranuclear Spin Cluster {Ni[(OH)2Cr(bispictn)]3}I5·5H2O. An Inelastic Neutron Scattering and Magnetic Study
- Author
-
Høgni Weihe, Ralph Schenker, Grégory Chaboussant, Hans U. Güdel, Michael Aebersold, Hanspeter Andres, Reto Basler, Kirsten Michelsen, and Herma Büttner
- Subjects
Inorganic Chemistry ,Physics ,Magnetization ,Crystallography ,Spin states ,Antiferromagnetism ,Physical and Theoretical Chemistry ,Spin (physics) ,Ground state ,Molecular physics ,Magnetic susceptibility ,Inelastic neutron scattering ,Ion - Abstract
The properties of the spin state manifold of the tetranuclear cluster Ni[(OH)(2)Cr(bispictn)](3)]I(5).5H(2)O (bispictn = N,N'-bis(2-pyridylmethyl)-1,3-propanediamine) are investigated by combining magnetic susceptibility and magnetization measurements with an inelastic neutron scattering (INS) study on an undeuterated sample of Ni[(OH)(2)Cr(bispictn)](3)]I(5).5H(2)O. The temperature dependence of the magnetic susceptibility indicates an S = (1)/(2) ground state, which requires antiferromagnetic interactions both between Cr(3+) and Ni(2+) ions and among the Cr(3+) ions. INS reveals potential single-ion anisotropies to be negligibly small and enables an accurate determination of the exchange parameters. The best fit to the experimental energy level diagram is obtained by an isotropic spin Hamiltonian H = J(CrNi)(S(1)().S(4)() + S(2)().S(4)() + S(3)().S(4)()) + J(CrCr)(S(1)().S(2)() + S(1)().S(3)() + S(2)().S(3)()) with J(CrNi) = 1.47 cm(-)(1) and J(CrCr) = 1.25 cm(-)(1). With this model, the experimental intensities of the observed INS transitions as well as the temperature dependence of the magnetic data are reproduced. The resulting overall antiferromagnetic exchange is rationalized in terms of orbital exchange pathways and compared to the situation in oxalato-bridged clusters.
- Published
- 2002
46. Oxo-bridged dinuclear chromium(III) complexes: correlation between the optical and magnetic properties and the basicity of the oxo bridge
- Author
-
Thorbjørn J. Morsing, Høgni Weihe, Anders Døssing, and Jesper Bendix
- Subjects
Methyl isocyanide ,chemistry.chemical_element ,Crystal structure ,Acid dissociation constant ,Inorganic Chemistry ,chemistry.chemical_compound ,Chromium ,Bipyridine ,Crystallography ,chemistry ,Density functional theory ,Valence bond theory ,Physical and Theoretical Chemistry ,Homoleptic - Abstract
The synthesis and X-ray structure of a new member of the series of oxo-bridged, dinuclear chromium(III) complexes, the methyl isocyanide complex [(CH3NC)5CrOCr(CNCH3)5](PF6)4·2CH3CN, is reported. This constitutes only the third oxo-bridged, dinuclear chromium(III) complex with a homoleptic auxillay ligand sphere. Experimentally, the system shows unshifted narrow nuclear magnetic resonance (NMR) spectra that are consistent with calculations using broken symmetry density functional theory (DFT), which suggests it to be the strongest coupled, dinuclear chromium(III) complex known. Furthermore, we report the crystal structure and computed magnetic properties for [(bpy)2(SCN)CrOCr(NCS)(bpy)2](ClO4)2·2H2O (bpy = 2,2'-bipyridine), which differs from other reported oxo-bridged species by featuring a bent CrOCr(4+) core. We also interpret the spectacular 10-orders-of-magnitude variation in acid dissociation constant of the bridging hydroxo ligand in mono hydroxo-bridged dinuclear chromium(III) complexes, in terms of a valence bond model parametrized by metal-to-metal charge transfer (MMCT) and ligand-to-metal charge transfer (LMCT) energies.
- Published
- 2014
47. Magnetic Interactions through Fluoride: Magnetic and Spectroscopic Characterization of Discrete, Linearly Bridged Mn-2(III)(mu-F)F-4(Me(3)tacn)(2) (PF6)
- Author
-
Hannu Mutka, Jesper Bendix, Torben Birk, Anne-Laure Barra, Christian Aa. Thuesen, Høgni Weihe, Marc Sigrist, Kim Pilkjær Simonsen, Kasper S. Pedersen, and Andrew D. Bond
- Subjects
Coupling constant ,010405 organic chemistry ,Exchange interaction ,Inorganic chemistry ,chemistry.chemical_element ,Manganese ,010402 general chemistry ,01 natural sciences ,Inelastic neutron scattering ,INELASTIC NEUTRON-SCATTERING SINGLE-MOLECULE MAGNETS ANTIFERROMAGNETIC SUPEREXCHANGE INTERACTIONS SPIN MANGANESE(III) COMPLEXES TRANSITION-METAL DIMERS EXCHANGE INTERACTIONS CRYSTAL-STRUCTURES CLUSTER CHEMISTRY LAYER STRUCTURE HIGH-FREQUENCY ,0104 chemical sciences ,law.invention ,Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,law ,Antiferromagnetism ,Physical chemistry ,Density functional theory ,Physical and Theoretical Chemistry ,Electron paramagnetic resonance ,Fluoride - Abstract
The nature of the magnetic interaction through fluoride in a simple, dinuclear manganese(III) complex (1), bridged by a single fluoride ion in a perfectly linear fashion, is established by experiment and density functional theory. The magnitude of the antiferromagnetic exchange interaction and the manganese(III) zero-field-splitting parameters are unambiguously determined by inelastic neutron scattering to yield J = 33.0(2) cm(-1) ((H) over cap = J (S-1) over cap.(S-2) over cap Hamiltonian definition) and single-ion D = -4.0(1) cm(-1). Additionally, high-field, high-frequency electron paramagnetic resonance and magnetic measurements support the parameter values and resolve vertical bar E vertical bar approximate to 0.04 cm(-1). The exchange coupling constant (J) is 1 order of magnitude smaller than that found in comparable systems with linear oxide bridging but comparable to typical magnitudes through cyanide, thus underlining the potential of fluoride complexes as promising building blocks for novel magnetic systems.
- Published
- 2014
48. ReF6]2-: A Robust Module for the Design of Molecule-Based Magnetic Materials
- Author
-
Morten Gotthold Vinum, Høgni Weihe, Mikkel Sørensen, Marc Sigrist, Christian Aa. Thuesen, Rodolphe Clérac, Kasper S. Pedersen, Jesper Bendix, Hannu Mutka, Stergios Piligkos, Anne-Laure Barra, Thomas Weyhermüller, Department of Chemistry [Copenhagen], Faculty of Science [Copenhagen], University of Copenhagen = Københavns Universitet (KU)-University of Copenhagen = Københavns Universitet (KU), Centre de recherches Paul Pascal (CRPP), Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut Laue-Langevin (ILL), ILL, Laboratoire national des champs magnétiques intenses - Grenoble (LNCMI-G), Université Joseph Fourier - Grenoble 1 (UJF)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Max Planck Institute for Chemical Energy Conversion, Max-Planck-Gesellschaft, Laboratoire national des champs magnétiques intenses - Grenoble [2009-2015] (LNCMI-G [2009-2015]), Department of chemistry, IT University of Copenhagen, and Centre National de la Recherche Scientifique (CNRS)
- Subjects
Coordination polymer ,Catalysis ,law.invention ,Magnetization ,chemistry.chemical_compound ,Nuclear magnetic resonance ,law ,[CHIM.COOR]Chemical Sciences/Coordination chemistry ,Anisotropy ,Electron paramagnetic resonance ,Fluoride ,Magnetic anisotropy ,ComputingMilieux_MISCELLANEOUS ,Magnetization dynamics ,[PHYS.PHYS.PHYS-ATM-PH]Physics [physics]/Physics [physics]/Atomic and Molecular Clusters [physics.atm-clus] ,Relaxation (NMR) ,General Chemistry ,[CHIM.MATE]Chemical Sciences/Material chemistry ,Magnetic susceptibility ,Coordination polymers ,Crystallography ,Rhenium ,chemistry ,Single-molecule magnets ,[PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph] - Abstract
A facile synthesis of the [ReF6 ](2-) ion and its use as a building block to synthesize magnetic systems are reported. Using dc and ac magnetic susceptibility measurements, INS and EPR spectroscopies, the magnetic properties of the isolated [ReF6 ](2-) unit in (PPh4 )2 [ReF6 ]⋅2 H2 O (1) have been fully studied including the slow relaxation of the magnetization observed below ca. 4 K. This slow dynamic is preserved for the one-dimensional coordination polymer [Zn(viz)4 (ReF6 )]∞ (2, viz=1-vinylimidazole), demonstrating the irrelevance of low symmetry for such magnetization dynamics in systems with easy-plane-type anisotropy. The ability of fluoride to mediate significant exchange interactions is exemplified by the isostructural [Ni(viz)4 (ReF6 )]∞ (3) analogue in which the ferromagnetic Ni(II) -Re(IV) interaction (+10.8 cm(-1) ) dwarfs the coupling present in related cyanide-bridged systems. These results reveal [ReF6 ](2-) to be an unique new module for the design of molecule-based magnetic materials.
- Published
- 2014
49. Fourth-order zero-field splitting parameters of [Mn(cyclam)Br2]Br determined by single-crystal W-band EPR
- Author
-
August Bouwen, Etienne Goovaerts, P. ter Heerdt, Susanne Mossin, Mariana Stefan, and Høgni Weihe
- Subjects
Solid-state physics ,Condensed matter physics ,Analytical chemistry ,Zero field splitting ,Atomic and Molecular Physics, and Optics ,Spectral line ,law.invention ,chemistry.chemical_compound ,Tetragonal crystal system ,chemistry ,law ,Cyclam ,Electron paramagnetic resonance ,Ground state ,Single crystal - Abstract
Single-crystal W-band (95 GHz) electron paramagnetic resonance (EPR) studies have been performed at 20 K and at room temperature on a tetragonal Mn(III) compound with potential application as a building block for high-spin clusters. The observed EPR spectra correspond to an anisotropic high-spinS = 2 ground state and have been attributed to equivalent centers related by four-fold symmetry. Accurate values for the spin Hamiltonian parameters were obtained from the analysis of the data at both temperatures. At 20 K the contribution of fourth-order zero-field splitting terms was shown to be significant, with parameter values B 4 0 = 0.0009(3) cm−1, B 4 2 = 0.0006(2) cm−1 and B 4 4 = 0.0017(3) cm−1, to be considered together with the second-order parametersD = −1.1677(7) cm−1 andE= −0.0135(6) cm−1.
- Published
- 2001
50. Ferromagnetic Exchange in the Ground and 4A1 Excited States of (Et4N)3Fe2F9. A Magnetic and Optical Spectroscopic Study
- Author
-
Hans U. Güdel, Ralph Schenker, and Høgni Weihe
- Subjects
Condensed matter physics ,Chemistry ,Physics::Optics ,Crystal growth ,equipment and supplies ,Magnetic susceptibility ,Optical absorption spectra ,Inorganic Chemistry ,Ferromagnetism ,Condensed Matter::Superconductivity ,Excited state ,Condensed Matter::Strongly Correlated Electrons ,Physical and Theoretical Chemistry ,human activities - Abstract
The synthesis, crystal growth, magnetic susceptibility, and polarized optical absorption spectra in the visible and near UV of (Et(4)N)(3)Fe(2)F(9) are reported. From single-crystal magnetic susceptibility data and high-resolution absorption spectra in the region of the (6)A(1) --(4)A(1) spin-flip transition, exchange splittings in the ground and excited states are derived. Ferromagnetic ground and excited state exchange parameters J(GS) = -1.55 cm(-1) and J(ES) = -0.53 cm(-1) are determined, respectively, and the relevant orbital contributions to the net exchange are derived from the spectra. The results are compared with those reported earlier for the structurally and electronically analogous [Mn(2)X(9)](5-) pairs in CsMgX(3):Mn(2+) (X = Cl(-), Br(-)), in which the splittings are antiferromagnetic. This major difference is found to be due to the increased metal charge of Fe(3+) compared to Mn(2+), leading to orbital contraction and thus to a strong decrease of the orbital overlaps and hence the antiferromagnetic interactions.
- Published
- 2001
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