A new series of rod-like conjugated molecules with a pyrazine or a bipyrazine core. Synthesis and light emitting properties

In this paper, we describe the synthesis of a wide range of new rod-like conjugated molecules with a pyrazine or a bipyrazine core connected to electron acceptor (A) or donor (D) groups through π-conjugated bridges as transmitters for the internal charge transfer (ICT). The key steps of the synthesis involve metallation and subsequent transmetallation of 2-chloropyrazine derivatives followed by Sonogashira or Negishi cross-coupling reactions. The bipyrazine core was obtained with a Stille cross-coupling reaction between the 2-chloro-6-tributylstannylpyrazine and the 2-chloro-6-iodopyrazine. Functionalization of the 6,6′-dichloro-2,2′-bipyrazine was performed by metallation, transmetallation and cross-coupling reactions. The light emitting properties of the so obtained molecules are then investigated in terms of absorption and emission spectra.