New oligomers with alternating phenylene ethynylene pyridinylene structure

The new 1,4-diethynyl aniline derivatives la and 1b were synthesized and successfully used in a Sonogashira cross-coupling reaction with 2,5-dibromopyridine. While the alternating oligomer 2a is soluble in THF or chloroform, oligomer 2b with a N,N-dioctylgroup in the phenylene repeating unit is insoluble in organic solvents. A possible explanation can be given by strong intermolecular interactions between pyridine and the dialkyl substituted aromatic ring. The absorption maximum of 2a is at 380 nm.