The research comprised in the thesis covers three topics:
An investigation of the mode of polymerisation and charge-transfer
mechanism of the polymerised form of bis-(3-thienyl)-1,3-dithiole-2-one. This was achieved in the preparation of 1,2-bis-(2-methyl-thiophen-3-yl) 2-hydroxyethylethanone and 1,2-bis-(2,5-dimethyl-thiophen-3-yl) 2-hydroxyethyl-ethanone and by investigating the electrochemical and spectroelectrochemical properties of 1,2-dithienylethylene. The results showed that bis-(3-thienyl)-1,3-dithiole-2-one undergoes an intramolecular cyclisation during the polymerisation process, adopting a quinoidal structure with charge-transfer properties similar to that of polyacetylene.
In all cases X-ray crystallographic data was obtained.
An in-situ chemical modification of the polymerised bis-(3-thienyl)-1,3-
dithlole-2-one was performed resulting in the preparation of a TIF derivatised
polythiophene. This provided further evidence in regard to the elucidation of mode of polymerisation and charge-transfer when spectroelectrochemical and
electrochemical studies were carried out. The monomeric unit 2-( 4,5-di-thiophen-3-yl-[1,3] dithio1-2-ylidine)-benzo[l,3]dithiole was produced allowing a comparative study to be performed with its X-ray crystal structure being obtained.
A further aim of the research was the attempted preparation of 1,3,6,7-
tetrathia-trinden-2-one in an effort to provide further evidence of the polymerisation mechanism of bis-(3-thienyl)-1,3-dithiole-2-one. The synthesis was found to be unsuccessful.
Finally, the photochemcial transformation of bis-(3-thienyl)-1,3-dithiole-2-
one in an effort to prepare 1,3,6,7-tetrathia-trinden-2-one was attempted. This
resulted in the formation of thieno[3,4-c]dithiine, the first example of a
transformation of this type.
Once understood, TTF derivatised polythiophenes based on 12 would be
prepared and polymerised. Within this rationale there are several approaches to
take; direct electropolymerisation, and in situ polymer modification as shown m
scheme 2.0.1 .
Scheme 2.0.1 Strategy for in situ polymer modification.
A further aim of the research was to prepare benzobithiophenes based on the
unit 13 (figure 2.0.1), in which the two thiophene rings have been fused together, in order that we might investigate the possibility of allowing direct polymerisation of TIF derivatives based on 14. This was attempted using synthetic andphotochemical methodologies.