Antiferromagnetic coupling of transition metal spins across pyrimidine and pyrazine bridges in dinuclear manganese(ii), cobalt(ii), nickel(ii) and copper(ii) 1,1,1,5,5,5-hexafluoropentane-2,4-dionate complexes

2002 ◽  
pp. 3177-3186 ◽  
Author(s):  
Takayuki Ishida ◽  
Takashi Kawakami ◽  
Shin-ichi Mitsubori ◽  
Takashi Nogami ◽  
Kizashi Yamaguchi ◽  
...  
Keyword(s):  
Transition Metal ◽  
Antiferromagnetic Coupling

Transition Metal Thiocyanate Complexes of Picolylcyanoacetamides

2017 ◽  
Vol 70 (5) ◽  
pp. 516 ◽  
Author(s):  
Yuniar P. Prananto ◽  
Aron Urbatsch ◽  
Boujemaa Moubaraki ◽  
Keith S. Murray ◽  
David R. Turner ◽  
...  
Keyword(s):  
Transition Metal ◽  
Transition Metal Complexes ◽  
Short Range ◽  
Sodium Thiocyanate ◽  
Antiferromagnetic Coupling ◽  
Carbonyl Groups ◽  
Ambient Conditions ◽  
One Dimensional ◽  
Thiocyanate Complexes ◽  
Solid State Structures

A variety of transition metal complexes involving picolylcyanoacetamides (pica = NCCH2CONH-R; R = 2-picolyl- (2pica), 3-picolyl- (3pica), 4-picolyl- (4pica)) and thiocyanate have been synthesised and their solid-state structures have been determined. The complexes were all obtained from reactions between the corresponding metals salts and pica ligands with sodium thiocyanate under ambient conditions. Both 3pica and 4pica coordinate to the metal solely through the nitrogen atom of the picolyl group and form discrete tetrahedral [M(NCS)2(pica)2] (3pica; M = Mn, Zn; 4pica; M = Co) and octahedral [M(NCS)2(3pica)4] (M = Co, Fe, Ni) complexes. In addition, one-dimensional N,S-thiocyanate-bridged coordination polymers poly-[M(µ-NCS)2(pica)2] (3pica; M = Cd; 4pica; M = Co, Cd) were obtained. The ligand 2pica gave the discrete octahedral complexes [Co(NCS)2(2pica)2] and [Cd(NO3)2(2pica)2] in which 2pica chelates in a bidentate fashion through its picolyl and carbonyl groups. Magnetic susceptibility measurements on the cobalt(ii) complexes were performed and showed short-range antiferromagnetic coupling for the [Co(NCS)2(4pica)2]n 1D polymer.

scholarly journals Chiral, Heterometallic Lanthanide–Transition Metal Complexes by Design

Inorganics ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 72 ◽  
Author(s):  
Anders Øwre ◽  
Morten Vinum ◽  
Michal Kern ◽  
Joris van Slageren ◽  
Jesper Bendix ◽  
...  
Keyword(s):  
Transition Metal ◽  
Transition Metal Complexes ◽  
Lewis Acids ◽  
Antiferromagnetic Coupling ◽  
Relaxation Processes ◽  
Coordination Geometry ◽  
Ferromagnetic Coupling ◽  
Metal Acetylacetonates ◽  
Metal Centers ◽  
Tunneling Pathways

Achieving control over coordination geometries in lanthanide complexes remains a challenge to the coordination chemist. This is particularly the case in the field of molecule-based magnetism, where barriers for magnetic relaxation processes as well as tunneling pathways are strongly influenced by the lanthanide coordination geometry. Addressing the challenge of design of 4f-element coordination environments, the ubiquitous Ln(hfac)3 moieties have been shown to be applicable as Lewis acids coordinating transition metal acetylacetonates facially leading to simple, chiral lanthanide–transition metal heterodinuclear complexes. The broad scope of this approach is illustrated by the synthesis of a range of such complexes LnM: LnM(hfac)3(μ2-acac-O,O,O′)3 (Ln = La, Pr, Gd; M = Cr, Fe, Ga), with approximate three-fold symmetry. The complexes have been crystallographically characterized and exhibit polymorphism for some combinations of 4f and 3d metal centers. However, an isostructural set of systems spanning several lanthanides which exhibit spontaneous resolution in the orthorhombic Sohncke space group P212121 is presented here. The electronic structure and ensuing magnetic properties have been studied by EPR spectroscopy and magnetometry. The GdFe, PrFe, and PrCr complexes exhibit ferromagnetic coupling, while GdCr exhibits antiferromagnetic coupling. GdGa exhibits slow relaxation of the magnetization in applied static fields.

Quinoxaline radical-bridged transition metal complexes with very strong antiferromagnetic coupling

2020 ◽  
Vol 56 (64) ◽  
pp. 9122-9125 ◽  
Author(s):  
Dimitris I. Alexandropoulos ◽  
Kuduva R. Vignesh ◽  
Haomiao Xie ◽  
Kim R. Dunbar
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Theoretical Calculations ◽  
Antiferromagnetic Coupling ◽  
Magnetic Studies ◽  
New Family

Synthesis, magnetic studies and, theoretical calculations of a new family of transition metal complexes bridged by a quinoxaline-based radical.

Magnetic Properties of GaN Layers Implanted by Mn, Cr or V.

2004 ◽  
Vol 825 ◽  
Author(s):  
Vitaliy A. Guzenko ◽  
Nicolas Thillosen ◽  
Andre Dahmen ◽  
Raffaella Calarco ◽  
Thomas Schäpers ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Properties ◽  
Transition Metal ◽  
Transition Metal Ions ◽  
Nitrogen Atmosphere ◽  
Antiferromagnetic Coupling ◽  
Implantation Energy ◽  
Paramagnetic Behavior ◽  
Sapphire Substrates ◽  
Different Temperatures

AbstractWe report on magnetic properties of the GaN layers implanted with 3d transition metal ions. GaN layers grown by MOVPE on sapphire substrates, p- or n-doped, were implanted by Mn, Cr or V ions with a dose of 5×1016 cm−2 and implantation energy of 200 keV. Subsequently, a rapid thermal annealing in nitrogen atmosphere for 5 minutes at different temperatures (700°C – 1050°C) was performed. The magnetization as a function of magnetic field as well as the dependence on temperature revealed paramagnetic behavior for all samples. In addition, an antiferromagnetic coupling between implanted ions was found.

HREM Study of electron-induced surface radiation damage in ReO3

1991 ◽  
Vol 49 ◽  
pp. 636-637
Author(s):  
R. Ai ◽  
H.-J. Fan ◽  
L. D. Marks
Keyword(s):  
Transition Metal ◽  
Metal Ions ◽  
Metal Oxides ◽  
Electron Irradiation ◽  
Transition Metal Oxides ◽  
Carbon Film ◽  
Transition Metal Ions ◽  
Surface Radiation ◽  
Valence Transition ◽  
Electron Microscopes

It has been known for a long time that electron irradiation induces damage in maximal valence transition metal oxides such as TiO2, V2O5, and WO3, of which transition metal ions have an empty d-shell. This type of damage is excited by electronic transition and can be explained by the Knoteck-Feibelman mechanism (K-F mechanism). Although the K-F mechanism predicts that no damage should occur in transition metal oxides of which the transition metal ions have a partially filled d-shell, namely submaximal valence transition metal oxides, our recent study on ReO3 shows that submaximal valence transition metal oxides undergo damage during electron irradiation.ReO3 has a nearly cubic structure and contains a single unit in its cell: a = 3.73 Å, and α = 89°34'. TEM specimens were prepared by depositing dry powders onto a holey carbon film supported on a copper grid. Specimens were examined in Hitachi H-9000 and UHV H-9000 electron microscopes both operated at 300 keV accelerating voltage. The electron beam flux was maintained at about 10 A/cm2 during the observation.

Problems with oxygen analysis in the system MgO-Al2O3-SiO2 with the electron microprobe

1992 ◽  
Vol 50 (2) ◽  
pp. 1624-1625
Author(s):  
Michel Fialin ◽  
Guy Rémond
Keyword(s):  
Transition Metal ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Electrostatic Charge ◽  
Carbon Layer ◽  
Sample Holder ◽  
Rock Matrix ◽  
Electrical Discharges ◽  
Thin Carbon ◽  
Beam Instabilities

Oxygen-bearing minerals are generally strong insulators (e.g. silicates), or if not (e.g. transition metal oxides), they are included within a rock matrix which electrically isolates them from the sample holder contacts. In this respect, a thin carbon layer (150 Å in our laboratory) is evaporated on the sections in order to restore the conductivity. For silicates, overestimated oxygen concentrations are usually noted when transition metal oxides are used as standards. These trends corroborate the results of Bastin and Heijligers on MgO, Al2O3 and SiO2. According to our experiments, these errors are independent of the accelerating voltage used (fig.l).Owing to the low density of preexisting defects within the Al2O3 single-crystal, no significant charge buildup occurs under irradiation at low accelerating voltage (< 10keV). As a consequence, neither beam instabilities, due to electrical discharges within the excited volume, nor losses of energy for beam electrons before striking the sample, due to the presence of the electrostatic charge-induced potential, are noted : measurements from both coated and uncoated samples give comparable results which demonstrates that the carbon coating is not the cause of the observed errors.

Electron energy loss near edge structures of intermetallic alloys and grain boundaries in NiAl

1996 ◽  
Vol 54 ◽  
pp. 522-523
Author(s):  
G.A. Botton ◽  
C.J. Humphreys
Keyword(s):  
High Temperature ◽  
Transition Metal ◽  
Energy Loss ◽  
Grain Boundaries ◽  
Industrial Applications ◽  
Edge Structure ◽  
Structural Applications ◽  
Yield Behaviour ◽  
Late Transition ◽  
Metal Aluminides

Transition metal aluminides are of great potential interest for high temperature structural applications. Although these materials exhibit good mechanical properties at high temperature, their use in industrial applications is often limited by their intrinsic room temperature brittleness. Whilst this particular yield behaviour is directly related to the defect structure, the properties of the defects (in particular the mobility of dislocations and the slip system on which these dislocations move) are ultimately determined by the electronic structure and bonding in these materials. The lack of ductility has been attributed, at least in part, to the mixed bonding character (metallic and covalent) as inferred from ab-initio calculations. In this work, we analyse energy loss spectra and discuss the features of the near edge structure in terms of the relevant electronic states in order to compare the predictions on bonding directly with spectroscopic experiments. In this process, we compare spectra of late transition metal (TM) to early TM aluminides (FeAl and TiAl) to assess whether differences in bonding can also be detected. This information is then discussed in terms of bonding changes at grain boundaries in NiAl.

A new lithium diffusion model in layered oxides based on asymmetric but reversible transition metal migration

2020 ◽  
Vol 13 (4) ◽  
pp. 1269-1278 ◽  
Author(s):  
Kyojin Ku ◽  
Byunghoon Kim ◽  
Sung-Kyun Jung ◽  
Yue Gong ◽  
Donggun Eum ◽  
...  
Keyword(s):  
Transition Metal ◽  
Diffusion Model ◽  
Layered Oxides ◽  
Layered Oxide ◽  
Reversible Transition ◽  
Lithium Diffusion ◽  
Metal Migration

We propose a new lithium diffusion model involving coupled lithium and transition metal migration, peculiarly occurring in a lithium-rich layered oxide.

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