f-Block and d,f-BlockPhosphonate Cages:Synthesis, Structure andMagnetic Properties

UoM administered thesis: Phd

  • Authors:
  • Karzan Zangana

Abstract

'f-Block and d,f-Block Phosphonate Cages: Synthesis, Structure and Magnetic Properties' is a thesis submitted to The University of Manchester for the degree of Doctor of Philosophy in the Faculty of Engineering and Physical Sciences.Research into molecular magnetism has undergone a revival over the past two decades following the discovery of Single Molecule Magnetism (SMM). Compounds which show this property have the potential to increase the storage capacity of magnetic media by many orders of magnitude compared to current generation devices. Developments in the field have come from synthesis involving mainly simple bridging ligands such as carboxylates, alkoxides, pyridonates and heterocyclic ligands.The use of phosphonic acid ligands in the synthesis of 4f-phosphonate or 3d-4f phosphonate clusters has recently begun to be explored, primarily for interest into their magnetic properties. The present work builds on studies which show that the reaction of oxo-centred metal triangles with phosphonate ligands can generate larger clusters retaining some motifs of the starting material. There are only few examples on the use of lanthanide carboxylates, such as [Ln2(O2CtBu)6(HO2CtBu)6] (Ln = Dy, Gd, Tb, Ho or Er) and/or a preformed cluster [Cr(III)3(µ3-O)(O2CtBu)6(H2O)3][O2CtBu] in combination with phosphonate ligands. This work investigates the use of bi-metallic lanthanide and tri-metallic transition metal starting materials in conjunction with the flexible tertiary-butylphosphonic acid ligand, to yield novel 4f-phosphonate and 3d-4f cages. Several Cr-4f phosphonate cages have been obtained, where each structure contains two oxo-centred {Cr3} triangles, bridged by phosphonates and lanthanides. Additionally, new 4f-phosphonate clusters have been synthesised by treating tertiary-butylphosphonic acid ligand with lanthanide nitrate salts or preformed lanthanide dimers. A number of 4f-phosphonate cages reported in the thesis show interesting structural or magnetic properties, for example, {Ln10P6} is the largest 4f-phosphonate odd number metal ring centred by a tenth metal site, the {Gd8P6} cluster demonstrates interesting MCE properties, and the {Dy4P2} complex is shown to be an SMM.

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Original languageEnglish
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Award date31 Dec 2015