The synthesis and properties of novel π-conjugated 2,1,3-benzothiadiazole oligomers

A series of novel, 2,1,3-benzothiadiazole-based oligomers were synthesized by the self/cross-coupling reaction of monobromo-substituted benzothiadiazole compounds in a catalyst system comprising Pd(OAc)2/PEG (polyethylene glycol)/DMF. The oligomers displayed good linear correlation between Egopt (or λmax, abs or λmax, em) and the reciprocal of the numbers of the benzothiadiazole units. The LUMO values of the compounds decreased with increasing number of benzothiadiazole units on the backbone of the molecules.