Synthesis, Magnetism and Redox Properties of Verdazyl Radicals, Diradicals and Related Coordination Compounds
Date
2013-09-26
Authors
Anderson, Kevin James
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Abstract
Coordination compounds involving stable radicals represent a promising avenue
toward the design of new magnetic materials. In this respect, a series of new metalverdazyl
radical complexes has been prepared and their magnetic properties reported.
These systems can be envisioned as model systems designed to help elucidate the
fundamental electronic interactions between one paramagnetic metal ion and one
verdazyl radical that lead to magnetic exchange.
A new chelating verdazyl diradical has also been prepared and fully characterised.
The electronic ground state of this diradical species has been established through
magnetic and variable temperature electron paramagnetic resonance (VT-EPR) studies.
In an effort to expand the metal-radical model systems beyond simple 1:1 metal:radical
complexes, this verdazyl diradical was employed as a ligand to prepare a succession of
first row transition metal complexes. The magnetic properties of the resulting
coordination compounds have been studied in an effort to understand how the nature of
the metal-diradical magnetic exchange changes with the metal used.
In addition to the wide-spread interest in the magnetic properties of stable organic
radicals, there is a growing awareness of the redox properties of this class of compounds.
Electrochemical and spectroelectrochemical techniques were utilised to probe the redox
properties of a verdazyl diradical and a structurally similar verdazyl monoradical.
Coordination compounds involving the redox-inert metal zinc were also prepared and
their redox properties investigated. While the addition of zinc to the verdazyl diradical
had no significant impact on the magnetic properties of the diradical, there is a distinct
difference between the redox properties of the diradical itself and its zinc complex.
Coordination to zinc also affected the redox properties of the verdazyl monoradical,
although to a lesser extent than what was observed for the diradical.
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Keywords
magnetic, chelating, verdazyl, ligand