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Magnetic properties of dysprosium and uranium sandwich complexes based on cyclopentadienyl and fulvalenyl ligands

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Version 2 2023-08-14, 10:29
Version 1 2023-06-10, 00:07
thesis
posted on 2023-08-14, 10:29 authored by Mian He

The PhD thesis describes a research project that focuses primarily on a series of dysprosium metallocenium single-molecule magnets containing cyclopentadienyl and fulvalenyl ligands. The project aims to discover the influence of the various ligand types on the magnetic properties, including the exchange coupling.

An introduction to SMMs is described in the first chapter, which mainly shows a historical perspective, current theoretical models and synthesis strategies. Inspired with the previous achievement of cyclopentadienyl sandwich SMMs in the Layfield group, I have successfully synthesized several dimetallic and trimetallic dysprosium metallocene SMMs containing the bulky pentafulvalenyl ligand [(C5tBu2H2)2]2–, with the complexes also containing bridging borohydride ligands, as described in Chapters 2 and 3, respectively. The bridged polynuclear structures show a periodic improval in the SMM properties, such as an increase in the effective energy barrier to reversal of the magnetization, which is thought to be a consequence of the gradually diminishing influence of the borohydride ligands. The magnetic measurements and theoretical calculations also indicate that the quantum tunnelling of the magnetization (QTM) process is suppressed in the polynuclear system due to magnetic exchange.

In Chapter 4, I describe a dysprosocenium-based single-ion magnet, which is sandwiched by a mono-phospholyl ligand and a Cp* ligand. The near-linear metallocenium compound displays an excellent blocking temperature of 70 K and two separate energy barriers of 1410 cm–1 and 747 cm–1 due to two distinct Orbach processes. According to the AC magnetic susceptibility measurements, the compound unexpectedly gives two range of maxima in magnetic susceptibility (c'M and c''M), which is not observed in other reported phospholide samples.

In Chapter 5, two dimetallic uranocenium compounds are reported based on the fulvalenyl ligand, with additional iodide bridges. The dimetallic U(III)-U(III) sandwich structure gives distinct chemical reactivity as the iodide ligand cannot be removed, but resulting in a mixed-valence U(III)-U(IV) cation.

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  • Published version

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  • Chemistry Theses

Qualification level

  • doctoral

Qualification name

  • phd

Language

  • eng

Institution

University of Sussex

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  • Yes

Legacy Posted Date

2021-07-12

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