Author: Sarah Ouanounou
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Investigation of Structural and Magnetic Properties of First and Second Row Transition Metals with N, N', N and S, N, S Pincer-type Ligands
Author: Sarah Ouanounou
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
The Magnetism and Coordination Chemistry of Mononuclear and Polynuclear Complexes of Copper(II) and Other First Row Transition Metal Ions Derived from Open-chain Diazine (N-N) Ligands
Author: Zhiqiang Xu
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
This thesis describes the structures and the magnetic properties of the first row transition metal complexes containing open-chain diazine (N-N) moieties. The purpose of the research is to establish a magnetostructural correlation involving the N-N single bond bridge and to investigate the coordination chemistry of open-chain diazine ligands to the first row transition metal ions. A relevant literature search is presented in Chapter 1. -- Chapter 1 describes a general introduction to magnetic exchange in polynuclear copper complexes and a general review of the coordination chemistry of diazine (N2) bridged complexes. In Chapter 2, seventeen dicopper(II) complexes with five open-chain diazine ligands (PAHAP, PMHAP, PHMAP, PHAAP and PYPZ) are reported, in which the two copper(II) centers are bridged by a single N-N bond only. The X-ray structures of one ligand and twelve dinuclear copper(II) complexes were determined. Changing the ligands, together with varying the coligands leads to a situation where the dihedral angle between the copper planes can be varied from 75° to 168.5°. For small angles (less than 80°) ferromagnetic coupling prevails, whereas at larger angles antiferromagnetic exchange is observed between the copper(II) centers. The exchange integrals (-2J) vary from -24.4 to 210 cm−1. This is associated with the degree of alignment of the nitrogen p orbitals in the diazine bridge, and is supported by molecular orbital calculations on the complexes and appropriate models. Chapter 3 deals mainly with dinuclear copper(II) complexes containing two ligands bridging two metal centers. The dinuclear copper(II) complexes containing two N-N single bonds have no or very weak coupling because of orbital orthogonality and the twisting of the two copper planes around these two N-N single bonds. A dicopper complex containing mixed diazine bridges (pyridazine/N-N) shows weak antiferromagnetic coupling, and since the diazine unit in the aromatic ring system bridges two copper centers in an orthogonal manner, this net antiferromagnetic coupling occurs only through the open-chain diazine bridge. A tetranuclear copper complex contains two pairs of dicopper(II) centers bridged orthogonally by two μ2-1,1-azide anions with each pair of copper(II) centers bridged by one N-N single bond and one μ2-1,1-azide with a 119° azide bridge angle. The dihedral angle about the N-N single bond is 54°, which indicates either no coupling or weak ferromagnetic coupling via such a bridge. Therefore, the strong antiferromagnetic coupling (-2J = 246 cm−1 ) occurs only through the μ2-1,1-azide bridges between each pair of copper(II) centers, giving the first genuine example contradicting the spin polarization mechanism associated with azide bridges. In Chapter 4, a series of spiral-like dinuclear complexes of Mn(II), Fe(II), Fe(III), Co(II), Co(III) and Ni(II) ions containing three N-N single bonds with a formula [L3M2].(X)n.mH2O (L = PAHAP, PZHPZ; X = CIO4 or NO3; n = 4, 6) and a seven-coordinate Fe(III) complex are discussed. The X-ray structures of six of these complexes have been determined. Variable-temperature magnetic properties, electrochemistry and spectra are discussed. Chapter 5 discusses the synthesis, structural and magnetic properties of some mononuclear and polynuclear first row transition metal complexes of the open-chain diazine ligands. The X-ray structures of eight complexes were determined. Two new coordination modes for open-chain diazine ligands have been found. In the last chapter, a general conclusion about coordination modes, magnetostructural correlations, etc. of the open-chain diazine complexes is made.
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
This thesis describes the structures and the magnetic properties of the first row transition metal complexes containing open-chain diazine (N-N) moieties. The purpose of the research is to establish a magnetostructural correlation involving the N-N single bond bridge and to investigate the coordination chemistry of open-chain diazine ligands to the first row transition metal ions. A relevant literature search is presented in Chapter 1. -- Chapter 1 describes a general introduction to magnetic exchange in polynuclear copper complexes and a general review of the coordination chemistry of diazine (N2) bridged complexes. In Chapter 2, seventeen dicopper(II) complexes with five open-chain diazine ligands (PAHAP, PMHAP, PHMAP, PHAAP and PYPZ) are reported, in which the two copper(II) centers are bridged by a single N-N bond only. The X-ray structures of one ligand and twelve dinuclear copper(II) complexes were determined. Changing the ligands, together with varying the coligands leads to a situation where the dihedral angle between the copper planes can be varied from 75° to 168.5°. For small angles (less than 80°) ferromagnetic coupling prevails, whereas at larger angles antiferromagnetic exchange is observed between the copper(II) centers. The exchange integrals (-2J) vary from -24.4 to 210 cm−1. This is associated with the degree of alignment of the nitrogen p orbitals in the diazine bridge, and is supported by molecular orbital calculations on the complexes and appropriate models. Chapter 3 deals mainly with dinuclear copper(II) complexes containing two ligands bridging two metal centers. The dinuclear copper(II) complexes containing two N-N single bonds have no or very weak coupling because of orbital orthogonality and the twisting of the two copper planes around these two N-N single bonds. A dicopper complex containing mixed diazine bridges (pyridazine/N-N) shows weak antiferromagnetic coupling, and since the diazine unit in the aromatic ring system bridges two copper centers in an orthogonal manner, this net antiferromagnetic coupling occurs only through the open-chain diazine bridge. A tetranuclear copper complex contains two pairs of dicopper(II) centers bridged orthogonally by two μ2-1,1-azide anions with each pair of copper(II) centers bridged by one N-N single bond and one μ2-1,1-azide with a 119° azide bridge angle. The dihedral angle about the N-N single bond is 54°, which indicates either no coupling or weak ferromagnetic coupling via such a bridge. Therefore, the strong antiferromagnetic coupling (-2J = 246 cm−1 ) occurs only through the μ2-1,1-azide bridges between each pair of copper(II) centers, giving the first genuine example contradicting the spin polarization mechanism associated with azide bridges. In Chapter 4, a series of spiral-like dinuclear complexes of Mn(II), Fe(II), Fe(III), Co(II), Co(III) and Ni(II) ions containing three N-N single bonds with a formula [L3M2].(X)n.mH2O (L = PAHAP, PZHPZ; X = CIO4 or NO3; n = 4, 6) and a seven-coordinate Fe(III) complex are discussed. The X-ray structures of six of these complexes have been determined. Variable-temperature magnetic properties, electrochemistry and spectra are discussed. Chapter 5 discusses the synthesis, structural and magnetic properties of some mononuclear and polynuclear first row transition metal complexes of the open-chain diazine ligands. The X-ray structures of eight complexes were determined. Two new coordination modes for open-chain diazine ligands have been found. In the last chapter, a general conclusion about coordination modes, magnetostructural correlations, etc. of the open-chain diazine complexes is made.
Magnetic and Structural Variability of First Row Transition Metal Complexes with Polyfunctional Ligands
Author: Miroslav Boča
Publisher:
ISBN:
Category :
Languages : en
Pages : 426
Book Description
Publisher:
ISBN:
Category :
Languages : en
Pages : 426
Book Description
Magnetic Properties of Layered Transition Metal Compounds
Author: L.J. de Jongh
Publisher: Springer Science & Business Media
ISBN: 9400918607
Category : Science
Languages : en
Pages : 430
Book Description
In the last two decades low-dimensional (low-d) physics has matured into a major branch of science. Quite generally we may define a system with restricted dimensionality d as an object that is infinite only in one or two spatial directions (d = 1 and 2). Such a definition comprises isolated single chains or layers, but also fibres and thin layers (films) of varying but finite thickness. Clearly, a multitude of physical phenomena, notably in solid state physics, fall into these categories. As examples, we may mention: • Magnetic chains or layers (thin-film technology). • Metallic films (homogeneous or heterogeneous, crystalline, amorphous or microcristalline, etc.). • I-d or 2-d conductors and superconductors. • Intercalated systems. • 2-d electron gases (electrons on helium, semiconductor interfaces). • Surface layer problems (2-d melting of monolayers of noble gases on a substrate, surface problems in general). • Superfluid films of ~He or 'He. • Polymer physics. • Organic and inorganic chain conductors, superionic conductors. • I-d or 2-d molecular crystals and liquid crystals. • I-d or 2-d ferro- and antiferro electrics.
Publisher: Springer Science & Business Media
ISBN: 9400918607
Category : Science
Languages : en
Pages : 430
Book Description
In the last two decades low-dimensional (low-d) physics has matured into a major branch of science. Quite generally we may define a system with restricted dimensionality d as an object that is infinite only in one or two spatial directions (d = 1 and 2). Such a definition comprises isolated single chains or layers, but also fibres and thin layers (films) of varying but finite thickness. Clearly, a multitude of physical phenomena, notably in solid state physics, fall into these categories. As examples, we may mention: • Magnetic chains or layers (thin-film technology). • Metallic films (homogeneous or heterogeneous, crystalline, amorphous or microcristalline, etc.). • I-d or 2-d conductors and superconductors. • Intercalated systems. • 2-d electron gases (electrons on helium, semiconductor interfaces). • Surface layer problems (2-d melting of monolayers of noble gases on a substrate, surface problems in general). • Superfluid films of ~He or 'He. • Polymer physics. • Organic and inorganic chain conductors, superionic conductors. • I-d or 2-d molecular crystals and liquid crystals. • I-d or 2-d ferro- and antiferro electrics.
First Principle Calculation of Structural and Magnetic Properties of Some Transition Metals and Their Multilayers
Author: 王柏凱
Publisher:
ISBN:
Category :
Languages : en
Pages : 98
Book Description
Publisher:
ISBN:
Category :
Languages : en
Pages : 98
Book Description
Homo- and Heteronuclear Transition Metal Clusters
Author: Stewart R. Parsons
Publisher:
ISBN:
Category : Ligands
Languages : en
Pages : 84
Book Description
Publisher:
ISBN:
Category : Ligands
Languages : en
Pages : 84
Book Description
The Electronic and Magnetic Properties of Some First Transition Metal Series Complexes of Diimine Ligands and Mossbauer and Magnetic Susceptibility Studies of Some Iron(II) and Iron(IV) Dithiocarbamate Complexes
Author: Bruce William Dockum
Publisher:
ISBN:
Category : Iron
Languages : en
Pages : 692
Book Description
Publisher:
ISBN:
Category : Iron
Languages : en
Pages : 692
Book Description
Investigation of One- and Two-dimensional Magnetic Behavior of Some First-row Transition Metal Compounds
Author: Harmen Tjeerd Witteveen
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
An Investigation Into the Structure and Magnetic Properties of Some Transition Metal-metalloid Alloys
Author: Eamonn Devlin
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Structural and Magnetic Properties of Metal(II) Complexes with Substituted Pyrazine Ligands
Author: Cheryl Falk Klein
Publisher:
ISBN:
Category :
Languages : en
Pages : 516
Book Description
Publisher:
ISBN:
Category :
Languages : en
Pages : 516
Book Description