Anisotropic displacement ellipsoid plot of 1 drawn at the 50% probability level showing the extended intra- and intermolecular π-system interactions with hydrogen atoms omitted. The  direction (c axis) is to the right. (See Fig. 2 for view down .) Symmetry-equivalent molecules were generated by crystallographic twofold screw axes with symmetry operators x, − y, − + z and x, − y, + z.