The synthesis of suitable model compounds for structural analysis of poly(isothianaphthene)-derivatives

Summary form only given. The low bandgap polymers are a very interesting research area among the other electroactive materials because of their significant ground state electrical conductivity. To get a fundamental understanding of structure-properties relationships it is essential to investigate the electronic structure of these materials. In recent years the electronic structure of poly(isothianaphtene) (PITN) has been studied from a theoretical viewpoint. PITN can be represented by two alternative forms, an aromatic and a quinoid one. In our research group previous /sup 13/C CP/MAS NMR investigations of PITN showed that it has a quinoid structure. In order to investigate this the /sup 13/C chemical shifts have to be compared with those of aromatic and quinoid model compounds. These specific model compounds need to have the following properties: they have to be synthesized and characterized in an easy way, they have to be soluble in commercial NMR-solvents and they have to be structural similar to the polymers. In this work the structure-properties relations of soluble alkoxy-PITN derivatives will be investigated. The advantage is that now high-resolution liquid NMR can be used instead of solid-state NMR and that applications are easier accessable. Of course low-molecular weight aromatic and quinoid model compounds are necessary for the investigation of the electronic structure. The synthesis of t-5,5´,6,6´-tetramethoxy-3,3´ bibenzo(c) thienyli-dene-1,1´-dion (quinoid model) and 1,3-dithienyl-5,6-dimethoxy isothianaphtene (aromatic model) will be presented.