Synthesis and Material Properties of Aromatic Cation-Centred Compounds

Abstract

Aromatic cations, such as cyclopropenium and tropylium, have access to delocalised electrons that spread the charge across their rings, enabling them to form stable ionic molecules.1 They are readily accessible species which makes them of interest for integration as part of functional materials.
In the field of ionic liquid crystals, while aromatic species such as imidazoliums have been widely investigated as part of molecular design of mesogens,2 the investigation of cyclopropeniums as part of liquid crystals has only just been undertaken.3 However, their molecular structure lends themselves to being the symmetrical core part of a discotic liquid crystal, while integrating a charged character to the material to give them potential as functional materials for electronic devices.
This thesis will discuss the synthesis of a range of cyclopropenium centred liquid crystals, which possess columnar liquid crystal phases and show a conductive character. The electron study revealed the preservation of a liquid-like conductivity of these materials into the liquid crystal and solid phases, and no conductive anisotropy in the liquid crystal phase. The initial synthesis and characterisation of a new series of aminocyclopropenium liquid crystals with greater thermal stability was also undertaken. In addition, attempts to adapt the procedures used for the tropylium species are discussed, including the challenges of applying this chemistry to the larger cation.