Crystal Structure and Optical Behavior of Diamino-Substituted 1,4-Benzoquinones

Reactions of benzoquinone with amines can potentially lead to the formation of coupled merocyanine or merocyanine/polymethine systems. In this study, several diamino-substituted 1,4-benzoquinones were synthesized. The crystal structures for three derivatives bearing 2-hydroxyethylamino or 2-(2-hydroxyethoxy)ethyl)amino substituents were determined using single-crystal X-ray crystallographic analysis. A characteristic feature of all molecular structures is the presence of an extensive network of intermolecular interactions, significantly stabilized by hydrogen bonding. Additionally, changes in the optical behavior of the synthesized compounds were monitored by UV-Vis spectroscopy in the presence of Cu2+ and Zn2+ ions, followed by the addition of primary, secondary or biogenic (butane-1,4-diamine) amines.