Magneto-structural correlations of iron-salicylaldoxime clusters : a dissertation presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemistry at Massey University, Turitea Campus, New Zealand

Thumbnail Image
Open Access Location
Journal Title
Journal ISSN
Volume Title
Massey University
The Author
The syntheses and characterisation of polynuclear metal clusters using a series of derivatised salicylaldoxime ligands are described in this thesis. The polynuclear iron clusters contain metallic cores consisting of oxo-centred triangles. It was found that slight modifications of the phenolic oxime ligands can lead to metal clusters with different nuclearities, thus producing a variety of magnetic properties within the materials. The predominant building block in the complexes is a triangular [Fe3O(Rsao) 3]+ (R = alkyl derivative, sao = salicylaldoxime) unit which can self-assemble into more complicated arrays depending on reaction conditions. A number of ligands containing a single phenolic oxime unit has been synthesised. These ligands have been used to form di-iron (C1), hexairon (C2), and heptairon (C3) complexes. A second series of ligands containing two double-headed phenolic oxime units linked by diamine straps has been synthesised and fully characterised. Two copper complexes C5 and C7 were crystallised and pyridine also took part in coordination to the copper centres. Three of the iron complexes formed with double-headed oxime ligands are heptairon compounds. The heptairon compounds were all analogous in their iron coordination environment. The hexairon complex (C8) formed from a double-headed oxime was analogous to the complex C2 formed from a single-headed oxime ligand in its iron coordination environment. The tri-iron complex (C10) also contains a metaborate ion. In each case of the heptairon complexes and the hexairon complex, the metallic skeleton of the cluster was based on a trigonal prism in which two [ O] triangles are fastened together via three helically twisted double-headed oxime ligands. Each of these ligands is present as (L-2H) where the oximic and phenolic O-atoms are deprotonated and the amino N-atoms protonated, with the oxime moieties bridging across the edges of the metal triangles. The identity of the metal ion has a major impact on the nuclearity and topology of the resultant cluster. The magnetic susceptibility measurements of these iron complexes suggest the presence of strong antiferromagnetic interactions between the metal centres and the Mössbauer analyses confirm the oxidation state of all the iron centres is 3+. The CHN analyses and other general characterisation allowed verifying and / or modifying the formulae generated by the X-ray analyses.
Metal clusters, Magnetic properties, Ligands, Iron, Copper