Synthesis of cobalt complexes towards single-molecule magnets: a structural and magnetic investigation

Sharp, Laura E. (2014) Synthesis of cobalt complexes towards single-molecule magnets: a structural and magnetic investigation. PhD thesis, University of Glasgow.

Abstract

The syntheses and characterisation of eighteen cobalt containing complexes are reported. These complexes range from simple monomers to complexes containing up to fourteen metal centres. Magnetic susceptibility measurements were carried out on ten complexes, to investigate the possibility of SMM properties.

Cobalt monomers were synthesised using the ligand, 2-Bis(2-hydroxyethyl)amino-2-(hydroxymethyl)-1,3-propanediol, “bis-tris” (H5L) and subsequently utilised as starting materials to form polynuclear complexes, a homometallic mixed valence Co10 complex (4) and a heterometallic {MnII5CoIII4} complex (5). Magnetic susceptibility measurements on both these complexes were complicated due to the presence of MII ions in multiple geometries.

A collection of complexes containing two to four metal centres was synthesised using the ligands diethanolamine and triethanolamine. Magnetic susceptibility measurements were carried out on a bromide bridged dimer (7), the CoII ions were found to be weakly ferromagnetically coupled and the complex has an effective spin ground state S′ = 1 with g > 4. A mixed valent tetramer (10) with two tetrahedral CoII ions was found to have antiferromagnetic interactions.

Five new seven-membered mixed valence disc complexes were synthesised; three homometallic and using the ligands diethanolamine, N-methyldiethanolamine and bis-tris propane; and two heterometallic discs that incorporated MnII ions, using the ligands 2-amino-2-(hydroxymethyl)-propane-1,3-diol, “tris” and diethanolamine (dea). Magnetic susceptibility measurements carried out on two homometallic Co7 discs, (11) and (12), found them to have an effective spin ground state S′ = 2 with g > 4. The magnetic properties of one heterometallic disc were measured [Co6Mn(dea)6(NO3)3][NO3]2 (15); it was not possible to clarify whether all MII-MII interactions occurring in this complex were ferromagnetic or whether other effects such as zero-field splitting were operative.
Of the larger complexes synthesised a homometallic Co10 (17 and 17a) complex was found to display predominantly ferromagnetic interactions. A novel heterometallic mixed valence ‘double disc’ complex with chloride bridges [Co12Mn2(NO3)4(dea)12Cl2][Cl]2[NO3]2 (18) was also synthesised.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Single-molecule magnets, Cobalt
• Subjects: Q Science > QD Chemistry
• Colleges/Schools: College of Science and Engineering > School of Chemistry
• Supervisor's Name: Murrie, Dr. Mark
• Date of Award: 2014
• Depositing User: Miss Laura E Sharp
• Unique ID: glathesis:2014-5259
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 13 Jun 2014 13:44
• Last Modified: 23 Jun 2017 12:13
• URI: https://theses.gla.ac.uk/id/eprint/5259