Towards polyyne rotaxanes and catenanes

Thesis

This thesis summarises attempts towards polyyne [n]rotaxanes and cyclocarbon [n]catenanes. Carbon allotropes built purely from sp carbon atoms have long fascinated chemists but have yet to be isolated or characterised due to their high reactivity. This thesis documents work towards isolating both linear and cyclic sp carbon chains.

Chapter 1 reviews the history of carbon allotropes, focussing on cyclic and linear forms of sp carbon. Synthetic strategies towards preparing acetylene-rich molecules, rotaxanes and catenanes are discussed.

Chapter 2 discusses development of a novel masked alkyne equivalent (MAE) with intrinsic metal binding abilities. A simple masked triyne can be synthesised in only three steps, but photochemical unmasking of this group could not be realised due to a competing dimerisation process.

Chapter 3 details new strategies for synthesising polyyne [3]rotaxanes with two macrocycles on the same polyyne thread. An active metal template route using dicobalt-masked precursors was developed to prepare two polyyne [3]rotaxanes. The thermal stabilities of the two rotaxanes were evaluated relative to the naked polyyne dumbbell and were found to be significantly more stable in decalin at 80 °C.

Chapter 4 presents a novel approach to cyclocarbon [n]catenanes and polyyne [n]rotaxanes. The coupling of a [2]rotaxane bearing two temporary bulky MAE stoppers provides access to precursors of cyclocarbon [n]catenanes and polyyne [n]rotaxanes. Early unmasking experiments have successfully afforded a polyyne bearing 24 contiguous acetylene units and indicate that larger polyynes should be viable using this route.

Chapter 5 summarises

Authors: Patrick, CW

• DOI: 10.5287/ora-xkz70mqn1
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: catenanes; polyynes; thermal stability; cyclocarbons; masked alkyne equivalents; acetylene; rotaxanes; template-directed synthesis
• Subjects: Supramolecular chemistry; Chemistry, Organic; Rotaxanes; Cyclocarbons; Polyynes; Catenanes