Spin State Modulation of Transition Metal Chelate Complexes

This thesis reports the synthesis and characterisation of 14 new Fe(III) complexes and a short study of a Mn(III) spin crossover complex by muon spin relaxation (µSR ) spectroscopy. Chapter 1 gives an introduction to the fundamentals of bonding in transition metal complexes, the theory behind spin crossover, a literature revision of Fe(III) spin states in related complexes, an explanation of muon spin relaxation spectroscopy and a brief review of the literature that has been published concerning the study of spin crossover systems by µSR. In Chapter 2 the synthesis and characterisation of 12 new mononuclear Fe(III) complexes is reported. The spin state of 7 of these was established as high spin by SQUID magnetometry, and single crystal diffraction indicates that all 12 are high spin at 100K. The structural features are compared with a known series of 10 mononuclear complexes with an isomeric ligand. Structural features of the total 22 Fe complexes from both isomeric series were examined to ascertain why one compound out of the set was low spin. Solid state IR and UV-Vis spectra of the 22 mononuclear complexes is also reported with UV-Vis data in acetonitrile solution. The spin state in DMSO-d6 was also probed by 1H NMR in three cases. Chapter 2 also reports structural data also reports structural data for 2 rearranged products, a mononuclear low spin Fe(III) complex and an xy dinuclear dimer. Finally temperature dependent muon absorption data on a known Mn(III) spin crossover (SCO) complex wth a stepped thermal profile is also reported. All experimental details are listed in Chapter 3.
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