Synthesis and Optical Properties of Acidochromic Amino-Substituted Distyryldiphenylpyrazines

Cruciforms with a distyryldiphenylpyrazine structure are prepared via aldol condensation of dimethylpyrazines and benzaldehydes. The structure is confirmed via X-ray diffraction and NMR spectroscopy, including 15N-NMR. The impact of basic and non-basic donor groups on the terminal positions, as well as the extension of the conjugated system by styryl groups on the optical properties, is studied. These quadrupolar dyes are solvatochromic in their absorption and more pronounced in their emission. TFA interacts with the basic sites, resulting in multiple changes in the optical spectra.