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Title: Towards stabilised cyclocarbons
Author: Kohn, Daniel R.
ISNI:       0000 0004 6501 1042
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2017
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This thesis describes synthetic efforts towards isolating cyclo[n]carbons. These elusive sp-hybridised allotropes of carbon have been synthetic targets for many years. Two modern stabilisation approaches are discussed that may provide the opportunity to finally prepare and study these molecules. Primarily, this thesis focuses on the stabilisation of sp-hybridised carbons by encapsulation with protective macrocycles. The concept of on-surface synthesis is also introduced and a method to prepare polyynes on surfaces using scanning probe microscopy is developed. These distinct approaches have simultaneously made significant progress in approaching cyclocarbons while enriching our understanding of polyynes. Chapter 1 reviews the history of carbon-rich molecules, experimental and theoretical studies of cyclocarbons and the concept of stabilising carbon chains via encapsulation. Chapter 2 explores the strategy of templating polyynes around a central core by preparing porphyrin-polyyne [3]- and [5]rotaxanes. There is also a photophysical investigation of excited state energy donation properties of polyynes. Chapter 3 details the synthesis of cobalt-masked polyynes and their mild unmasking. This unmasking process yields pristine polyynes in unprecedented yields and offers significant promise for the use of this method in cyclocarbon catenane synthesis. Chapter 4 summarises the synthesis of small macrocycles and dibromoolefin rotaxanes. These dibromoolefin rotaxanes have their protective silyl groups removed, yet remain interlocked. Chapter 5 introduces scanning probe microscopy and developments in on-surface synthesis. Furthermore, we develop the controlled synthesis of polyynes from dibromoolefins, using the Fritsch-Buttenberg-Wiechell rearrangement by atomic manipulation. Chapter 6 summarises the key results in this thesis and contains proposals for future work in this area.
Supervisor: Anderson, Harry L. Sponsor: ERC
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available