Crystal and Electronic Structures of Hydrogen-Bonded 2,5-Diamino-3,6-dihydroxy-<i>p</i>-benzoquinone

Shiny green-colored single crystals of 2,5-diamino-3,6-dihydroxy-p-benzoquinone (1) were prepared from 2,3,5,6-tetrahydroxy-p-phenylenediammonium dichloride. X-ray crystal structural analysis and ab initio calculations revealed that the molecular structure of 1, a highly polarized zwitterionic structure, was similar to that of p-benzoquinone rather than that of p-quinodiimine. Furthermore, a regular π-stack and an intermolecular two-dimensional hydrogen-bonding network were observed within the crystals of 1. The green color in the solid state was attributable to the intermolecular charge-transfer interactions.