Synthesis of Fluorescent oligo(p-phenyleneethynylene) (OPE3) via Sonogashira Reactions

Sonogashira reactions of 4-(2,5-diiodobenzoyl)morpholine and 4-(5-bromo-2-iodobenzoyl)morpholine with arylacetylenes catalyzed by Pd2(dba)3 in DMSO allowed preparation of fluorescent oligo( p-phenyleneethynylene)s (OPE3) with fluorescence quantum yields up to 0.87. DMSO proved to be very efficient for this double Sonogashira coupling in which other solvents failed.