Improved synthesis of 4-bromo-2,2′-bipyridine: A start material for low-molecular-weight model compounds

Abstract

An improved and simplified synthetic method for 4-bromo-2,2′-bipyridine (5) has opened a way to the synthesis of the model compounds 8a, b of polymer 9. 8a, b confirmed the effective conjugation segment of polymer 9 to consist of an alternation of three aryl and two ethynyl units (Ar-C≡C-Ar-C≡C-Ar) due to the zig-zag structure of the polymer. It was found to be the smallest conjugated unit necessary to obtain excellent fluorescence.