π-Extended fluorophores based on 5-aryl-2,2'-bipyridines: synthesis and photophysical studies

A straightforward and convenient synthesis of new fluorescent 5-aryl-2,2'-bipyridines with the extended conjugation system involves the ‘1,2,4-triazine’ methodology followed by Pd-catalyzed cross-coupling or Wittig reactions using 5-(4-bromophenyl)- or 5-(4-bromomethylphenyl)-2,2'-bipyridines as the starting materials. For these compounds, a pronounced bathochromic shift was observed in both absorption and emission spectra compared to previously reported 5-phenyl- 2,2'-bipyridine. For the one of the products, adsorption and fluorescent titrations were fulfilled, fluorescent response on the addition of metal cations was examined.