Synthesis of a Quinoxaline Dimer and Trimer via Yamamoto Coupling

Quinoxalines are an important class of compounds that can exhibit properties such as luminescence and liquid crystal phases. The corresponding quinoxaline dimers and their cyclotrimers, in contrast, have received little attention. We report the synthesis and characterization of a novel tetrakis(dialkoxyphenyl)biquinoxaline derivative (1), and the corresponding novel hexakis(dialkoxyphenyl)-1,4,7,10,13,16-hexaazatrinaphthylene (2) using the nickel-mediated Yamamoto coupling as a key step. The resulting compounds show solvent-dependent emission spectra in solution, suggesting a donor-acceptor architecture with charge separation in the excited state. A preliminary mesophase characterization reveals that both compounds also exhibit columnar mesophases, as shown by polarized optical microscopy and differential scanning calorimetry, and form glasses upon cooling to room temperature.