Synthesis and Photophysical Properties of a Series of Pyrazine‐Based Push–Pull Chromophores

Abstract

Eighteen push–pull pyrazine fluorophores are described. Methoxy, dimethylamino, and diphenylamino groups were used as electron‐donating groups (EDGs), and six π‐conjugated systems consisting of multiple bonds and 1,4‐phenylene moieties were used to connect the EDGs to the pyrazine core. The chromophores were obtained by Knoevenagel condensation and palladium‐catalyzed cross‐coupling reactions starting from commercially available 2‐methyl‐ or 2‐chloropyrazine. The optical absorption and emission properties of these chromophores were studied in different solvents. Some proved to be highly emissive and exhibit strong emission solvatochromism, which suggests a highly polar emitting state, characteristic of compounds that undergo intramolecular charge transfer (ICT). The influences of the various electron‐donating groups and π‐conjugated systems on the emission and ICT have been carefully studied.