Characterisation and screening of novel aromatic thin-film materials
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Date
04/2009Author
Henry, John B.
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Abstract
The electropolymerisation of a range of indole derivatives results in the formation of
redox active films. These redox films have been observed to be highly luminescent.
Earlier studies have investigated electrochemical and photophysical properties, for
potential applications such as fast response potentiometric sensors or novel materials
for light emitting devices. The work in this thesis extends this approach to
electrochemical and computational studies of a range of novel redox-active aromatic
systems.
This work has exploited the continuing increase of computing power, employing
powerful quantum computational models to complement and augment
electrochemical methods. Density Functional Theory has been used to show that
prediction of oxidation potentials in good agreement with experimental values is
achievable for a wide range of aromatic systems. Calculation of the electron spin
density of the radical cations has also helped to elucidate the likely coupling
locations for the formation of electroactive layers. It is observed that the nature of
substituents and additional hetero groups to the aromatic systems can have a
profound effect on electron spin density distributions.
The redox-active species formed from indole dimers and 5-methylindolocarbazole
have also been characterised. The species formed from electropolymerisation of 5-
methylindolocarbazole has been found to be a mixture of three isomers of a 5-
methylindolocarbazole dimer. Full characterisation of the product of the
electropolymerisation of indole dimers was not possible; fluorescence work however
suggests this to be a species with a greater degree of conjugation than either indole
dimers or trimers. It is thought likely that this product is either a tetramer or longer
chain polymer. This work demonstrates the applicability of a combination of
computational and electrochemical methods to the characterisation of novel
heteroaromatic systems.