Supramolecular arrays and clusters: from Cr7Ni to new Heterometallic Wheels containing spin centres

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Abstract

This thesis explores the use of bottom-up synthetic methods to make electronic spin based supramolecular systems and study their application in quantum computing. Incorporating such metal ions or clusters requires extensive knowledge of their magnetic properties since even small structural changes can have an observable effect in their magnetism, with differences in their axial and rhombic magnetic anisotropy, and their distance can be tailored to strengthen or weaken their interaction. The techniques used for the fundamental analysis of their magnetic properties include low and high-frequency Continuous Wave and Pulsed electron paramagnetic resonance (EPR) spectroscopy and SQUID magnetometry. The synthesis of a novel supramolecular assembly containing two functionalized {Cr7Ni} rings bridged by either a high spin lanthanide ion (Gd3+) or diamagnetic ion (Y3+) is introduced, along with an extensive characterisation of its electronic properties. Continuous Wave and Pulsed EPR measurements have allowed the determination of the sign and rhombicity of the anisotropy, the fine magnetic interaction between the components as well as the spin relaxation dynamics of the individual qubits. A series of reactions to create clusters of varying nuclearity and a new family of heterometallic {CrxMy} wheels (where M= Ti4+, Th4+, U4+/5+) are reported. The analysis of the magnetic measurements provides an overview of the changes in antiferromagnetic interaction between the Cr3+ depending on the capping heterometals. Finally, a new class of heterometallic wheels are presented that contain a single 3d transition metal in a diamagnetic circumference. For the Ti7M (where M= Fe3+, Cr3+) family, using the same wheel size but different counter cations, a correlation is drawn with the distortion on the Oh geometry of the paramagnetic ions and its effect on the transition metal̢۪s anisotropy using CW EPR. For the Ga7M (M= Cu2+, Mn2+) wheels, CW EPR spectroscopy in powder samples and solutions are used to elucidate the electronic structure of the divalent metal and hyperfine interactions from coordinated fluorides.

Keyword(s)

Coordination Chemistry; Electron Paramagnetic Resonance; Heterometallic Wheels; Molecular Magnetism; Quantum Information Processing

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