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Title: Solvothermal synthesis of novel vanadium (III) and chromium(III)clusters from simple starting materials
Author: Batchelor, Luke J.
ISNI:       0000 0004 2687 3854
Awarding Body: The University of Manchester
Current Institution: University of Manchester
Date of Award: 2010
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The solvothermal syntheses, in which reactions are performed in sealed vessels at temperatures greater than the solvent’s atmospheric pressure boiling point, of new VIII and CrIII clusters are reported. This technique has been shown to overcome difficulties associated with the air sensitivity and kinetic inertness of the two ions respectively. Chapter 2 describes the synthesis of an iso-structural series of Lindqvist type structures, of general formula (Hpy)2[M6O(thme)4Cl6], by reaction of the simple starting materials [MCl3(thf)3] (M = V, Cr and Fe) with pyridine, followed by addition of the triolate pro-ligand H3thme. The magnetic behaviour of these clusters was investigated and was shown to be dominated by anti-ferromagnetic exchange between the metal ions, resulting in singlet S = 0 ground states. The incorporation of chelating bipyridine in the synthesis and variation of reaction conditions described in chapter 3 yields “metal centred stars” such as [Cr4(tmp)2(bpy)3Cl6], for a range of triolato ligands. This triangular arrangement of ions was previously reported for FeIII and subsequently became one of the most well-studied single molecule magnets (SMMs). Magnetic susceptibility measurements exhibit behavior consistent with predominantly anti-ferromagnetic coupling interactions between metal centres and a resulting S = 3 ground state, however SMM behaviour was not observed. Some novel trithiolate cluster chemistry is discussed in chapter 4, including the synthesis of a range of thiolate bridged clusters, including [V3O(tmme)2(bpy)2Cl] and (HNEt3)2[V4O(tmme)4]. These are the first VIII-tmme clusters and display the rare three-coordinate T-shaped, and four-coordinate square-planar oxide coordination geometries. Magnetic measurements suggest incredibly strong antiferromagnetic exchange (> 200 cm-1) between adjacent vanadium ions in the preceding clusters, resulting in a triplet S = 1 ground state for the trimer and a diamagnetic response for the tetramer. DFT calculations suggest this behaviour is due to very strong V-S-V super-exchange rather than the formation of metal-metal bonds. The reactions of pro-ligands known to promote cluster formation, such as triethanolamine and p-tert-butylthiacalix[4]arene are discussed in chapter 5, and the first VIII and CrIII clusters directed by these ligands are reported.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available