Abstract
This dissertation presents the results of our work on the synthesis and structural
characterization of several families of coordination complexes as well as their study with
regard to their magnetic properties.
Chapter 1 provides a brief introduction in the field and theory of single-molecule magnets
(SMMs). Starting from the archetype SMM Mn12 we present the details of the mechanisms
governing the relaxation of the magnetization of these systems.
In Chapter 2 we present our work on the coordination chemistry of lanthanides with a new
Schiff-base ligand, H3L [(E)-3-((2-hydroxyphenyl)imino)- methyl)benzene-1,2-diol]. Using
this ligand, we were able to synthesize four different families of lanthanide complexes
framed by alkali metals. Throughout the chapter we demonstrate how we can exploit the
presence of the coordinated alkali metal ions in order to induce changes to the structure and
the nuclearity of the complexes. In addition, section 2.6 describes how we can, within the
same molecule, induce changes to the coordination environment of the lanthanide ions by
simple solvent substitution. Each section deals with a different family of complexes and a
detailed characterization of the static and dynamic magnetic properties of these complexes
is presented. A number of the reported complexes show single-molecule magnet behaviour
in zero or non-zero applied static magnetic field. For these systems a study of their dynamics
is presented and the mechanisms behind the relaxation are elucidated.
In Chapter 3 we present the results of our work with third row (3d) transition metal ions
and their complexes. Specifically, in section 2.1 we report a series of complexes synthesized
using a tripodal hexadentate Schiff-base ligand. The ligand demonstrates the ability to form
mononuclear or trinuclear complexes of M3+ or M2+ metal ions (M: 3d transition metal) with
the preference to either approximate octahedral or trigonal prismatic coordination geometry.
A detailed magnetic characterization for most of the complexes is presented where a
trinuclear Co2+ cluster stands out for its pronounced SMM behaviour below 8 K in zeroapplied
field.
Section 2.2 deals with the modelling of the magnetic properties of a Mn3+ [2 × 2] square grid
(Mn4) using a combination of magnetic susceptibility and magnetization measurements as
well as Inelastic Neutron Scattering (INS) and high-field Electron Paramagnetic Resonance
(HFEPR) spectroscopy. From the combination of these measurements we are able to
accurately determine the fine structure of the energy diagram of the spin states for Mn4.
Finally, in section 2.3 we present magnetostructural correlation studies of a series of double
oxime bridged Mn3+ dinuclear complexes. Based on the earlier experimental and theoretical
work of Brechin et al. we show how the relative orientation of the Jahn-Teller axes of the
Mn3+ ions, in combination with the torsion angle of the oxime bridge can affect the magnetic
exchange interaction between the two metal centers.
characterization of several families of coordination complexes as well as their study with
regard to their magnetic properties.
Chapter 1 provides a brief introduction in the field and theory of single-molecule magnets
(SMMs). Starting from the archetype SMM Mn12 we present the details of the mechanisms
governing the relaxation of the magnetization of these systems.
In Chapter 2 we present our work on the coordination chemistry of lanthanides with a new
Schiff-base ligand, H3L [(E)-3-((2-hydroxyphenyl)imino)- methyl)benzene-1,2-diol]. Using
this ligand, we were able to synthesize four different families of lanthanide complexes
framed by alkali metals. Throughout the chapter we demonstrate how we can exploit the
presence of the coordinated alkali metal ions in order to induce changes to the structure and
the nuclearity of the complexes. In addition, section 2.6 describes how we can, within the
same molecule, induce changes to the coordination environment of the lanthanide ions by
simple solvent substitution. Each section deals with a different family of complexes and a
detailed characterization of the static and dynamic magnetic properties of these complexes
is presented. A number of the reported complexes show single-molecule magnet behaviour
in zero or non-zero applied static magnetic field. For these systems a study of their dynamics
is presented and the mechanisms behind the relaxation are elucidated.
In Chapter 3 we present the results of our work with third row (3d) transition metal ions
and their complexes. Specifically, in section 2.1 we report a series of complexes synthesized
using a tripodal hexadentate Schiff-base ligand. The ligand demonstrates the ability to form
mononuclear or trinuclear complexes of M3+ or M2+ metal ions (M: 3d transition metal) with
the preference to either approximate octahedral or trigonal prismatic coordination geometry.
A detailed magnetic characterization for most of the complexes is presented where a
trinuclear Co2+ cluster stands out for its pronounced SMM behaviour below 8 K in zeroapplied
field.
Section 2.2 deals with the modelling of the magnetic properties of a Mn3+ [2 × 2] square grid
(Mn4) using a combination of magnetic susceptibility and magnetization measurements as
well as Inelastic Neutron Scattering (INS) and high-field Electron Paramagnetic Resonance
(HFEPR) spectroscopy. From the combination of these measurements we are able to
accurately determine the fine structure of the energy diagram of the spin states for Mn4.
Finally, in section 2.3 we present magnetostructural correlation studies of a series of double
oxime bridged Mn3+ dinuclear complexes. Based on the earlier experimental and theoretical
work of Brechin et al. we show how the relative orientation of the Jahn-Teller axes of the
Mn3+ ions, in combination with the torsion angle of the oxime bridge can affect the magnetic
exchange interaction between the two metal centers.
| Original language | English |
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| Publisher | Department of Chemistry, Faculty of Science, University of Copenhagen |
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| Publication status | Published - 2016 |