The synthesis, structures and physical properties of fluoride and oxalate based magnetic coordination polymers

Abstract

This thesis describes the crystal structures and physical properties of three types of
organic-inorganic hybrid coordination polymers (CPs): organic-inorganic hybrid fluoride
layered perovskites, oxalate fluoride CPs and metal(III)-fluoride compounds. Most of the
compounds presented here were synthesised through hydrothermal and solvothermal reactions,
except two metal(III)-fluoride compounds which were synthesised by a layered solution
method.

For the organic-inorganic hybrid layered perovskites, seven compounds are reported.
The crystal structures are revealed by single crystal X-ray diffraction. The magnetic properties
of some have also been characterised by SQUID magnetometry, and the results show the metal
centres in all the compounds display antiferromagnetic interactions at high temperature. For
the compounds (enH₂)MnF₄ (1) and (enH₂)CoF₄ (2), variable temperature crystal structure
analysis has been carried by the powder synchrotron X-ray diffraction and powder neutron
diffraction. The results of Rietveld refinements show no phase transition was observed for both
compounds. The magnetic structure of 2 has also been determined from the neutron data, in
which the interactions of Co remain antiferromagnetic, with the magnetic moment (Mx0, My0,
Mz0) = (3.53, 0, 0.53) at 20 K. In addition, the crystal structures of two derived compounds
are also presented in this section.

For the oxalate fluoride compounds, nine crystal structures are also characterised by
single crystal X-ray diffraction. The compounds are in the form of 1D or 2D magnetic
structures which are constructed by the metal centres and versatile coordination modes of the
oxalate ligands. Magnetic characterisations show nearly all the compounds display
antiferromagnetic interactions at high temperature, which are all well fitted by the 1D
Heisenberg model.

The majority of the seven metal(III)-fluoride compounds contain monomeric units.
However, two unusual layered structures, which may form part of a homologous series, have
been discovered, and there are some relationships between the syntheses and structures which
can be applied in more targeted work in the future.

Date of Award	30 Jun 2020
Original language	English
Awarding Institution	University of St Andrews
Supervisor	Philip Lightfoot (Supervisor)