Fundamental Studies and Applications of Fluxional Carbon Cages

Abstract

Fluxional carbon cages, such as bullvalene and barbaralane, are molecules which possess ‘shapeshifting’ properties through the rapid and reversible Cope rearrangements inside their carbon skeletons. The existence of fluxional carbon cages has proven that a dynamic structural library can exist in a single rigid molecule and their isomerism distribution could be biased through covalent or noncovalent bonding.
Over the last 60 years, the development of fluxional carbon cages has been mostly focused on fundamental studies such as synthesis and computational modelling. There have been several examples of their fluxional properties being utilised in chemical and physical application, while their potential to be biological systems and functional materials has been rarely discovered.
Based on the most advanced synthetic methods of bullvalenes and barbaralanes, we have explored both their fundamental properties and potential applications. The noncovalent control over the dynamic chirality of 9-substituted barbaralanes was achieved in both solid and solution states and proved by X-ray diffractions and NMR spectroscopy, which explored the potential of barbaralanes building the induced-fit model. Various barbaralane oligomers were prepared and their dynamic preferential crystallisations were observed and analysed for future predictions of their crystalline
behaviours. Molecular glasses analogues of bullvalenes were synthesised and characterised, with their thermal properties were studied via differential scanning calorimetry and polarised microscopy, in which their spontaneous adjustment of crystallinity degree could lead them to be potential functional materials.