pi-Conjugated oligomers and polymers with a self-assembled ladder-like structure

A series of alternating polymers and well-defined oligomers, composed of 2,5-linked pyrazines and N,N'-diacylated phenylene-1,4-diamines were prepd. using the Stille cross-coupling. The presence of N-hydrogen bond acceptors and N-hydrogen bond donors in adjacent units induces intramol. hydrogen bonding and hence leads to spontaneous formation of a ladder-type structure in which the arylene units tend to become coplanar. Self-assembly of the ladder structure in soln. is convincingly demonstrated by NRM- and IR-spectroscopy. The acylation of the ortho-amine functionalities with lipophilic groups leads to strong hydrogen bonding and improve soly. These large ortho-substituents do not disturb the p-delocalization of the system