Synthesis of oligo(p-phenylene-m-pyridindiyl)s

Oligomers (7, 9, 11, and 13a-c), which consist of an alternate sequence of 1,4-linked benzene rings and 2,4-linked pyridine rings, were prepared from the corresponding oligochalcones. Each enone segment reacts with phenacylpy ridinium bromide (3) and ammonium acetate (4) to yield a pyridine building block. Propoxy sidechains attached on the benzene rings of the chalcones re duce to some extent the yield of the cyclization reactions (40-68%) but enh ance the solubility of the oligomers. Cross conjugation leads to a moderate bathochromic shift of the absorption with increasing number of repeating u nits.