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Title: The role of bis-calix[4]arenes in the synthesis of multi-component polymetallic clusters
Author: Coletta, Marco
ISNI:       0000 0004 7655 857X
Awarding Body: Heriot-Watt University
Current Institution: Heriot-Watt University
Date of Award: 2017
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The work presented in this thesis encompasses the synthesis of novel p-tert butylcalix[4]arene-based ligands with the overall aim of exploring and understanding their coordination chemistry. The ligands described have been obtained via substitution and functionalisation of p-tert-butylcalix[4]arene at one methylene bridge position, the mechanism of which is discussed in detail herein. Once isolated, these ligands were reacted with a selection of transition (TM), lanthanide metals (Ln) and 3d-4f metal ion mixtures in order to systematically study the formation of polymetallic clusters and their prevailing magnetic properties. This also provided the opportunity to gain insight into ligand influence over the associated coordination chemistry, all of which was possible through the growth and X-ray diffraction study of single crystals in each case. Chapter 1 contains an overview of calix[n]arene synthesis (and related derivatives), with a particular emphasis on calix[4]arene, its conformational properties, and synthetic modifications at the upper-, lower-rim and methylene bridge positions. Discussion then moves to a qualitative description of single-molecule magnets and molecular refrigerants, highlighting some of the seminal achievements in the area. The final section of Chapter 1 discusses the coordination properties of calix[4]arene, including the formation of metal clusters that represent the foundation of the work presented in Chapters 2 - 5. Chapter 2 presents the synthesis of 2,2'-biscalix[4]arene prior to discussion of the use of this ligand in reactions with TM / Ln ion mixtures, the results of which were the isolation of a series of 2,2'-biscalix[4]arene-supported 3d/4f metal clusters. This was carried out with a particular focus on stoichiometric control over cluster synthesis, which subsequently afforded novel cluster topologies that are closely related to species already obtained from previous research within the group. Chapter 3 covers exploratory cluster formation that was carried out using 2,2' biscalix[4]arene in the presence of complementary and competitive co-ligands. The co ligands employed were carefully chosen based on their known metal ion binding properties, resulting in dramatic changes to the topologies of the prevailing polymetallic clusters, the structures of which are described in detail. Chapter 4 describes a modified synthetic procedure that facilitated the isolation of a family of flexible alkyl chain tethered biscalix[4]arenes. These ligands were then used in exploratory cluster formation and afforded a series of known cluster topologies when the length of the alkyl tether permitted this. Structural discussion highlights these similarities and draws comparison with the TBC[4]-supported clusters presented in Chapter 1. Chapter 5 focuses on exploratory coordination chemistry that was carried out with rigidly tethered biscalix[4]arenes. The chapter begins with a brief description of the synthesis of these ligands before moving on to discussion of the new polymetallic clusters isolated, highlighting important structural analogies and differences with the architectures described in Chapters 1 and 4. Chapter 6 presents a summary of the work included in this thesis, as well as an outlook of future work to be undertaken in this area.
Supervisor: Dalgarno, Scott J. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available