Structure-property relationships in mixed oligoheterocycles based on end-capped oligothiophenes

Novel mixed oligoheterocycles 1-5, containing thiophene/thiazole, thiophene /1,3,4-thiadiazole, thiophene/oxazole, or thiophene/1,3,4-oxadiazole moieti es, were synthesized. The introduction of electronegative heteroatoms such as oxygen and nitrogen into the conjugated x-system leads to a more pronoun ced acceptor character than that found in the analogous oligothiophenes. Ch aracterization of the redox properties reveals that the reduction of the mi xed oligomers is facilitated while oxidation is shifted to higher potential s. For this series, clear structure-property relationships could be found b y comparing optical properties, in particular absorptions, emissions and fl uorescence quantum yields in solution. The X-ray structural determination o f mixed thiophene/1,3,4-oxadiazole heptamer 5 indicates that the replacemen t of thiophene units by 1,3,4-oxadiazoles has a strong influence on the mol ecular arrangement and intermolecular interactions in the solid state.