Fig. 1. Calculated minimum energy structures for (a) CQ0 monomer; (b) equilibrium geometry of π-stacked (CQ0)2–, adopting a distorted sandwich geometry. The excess electron is localised on the left (planar) monomer in the ground electronic state. The right (non-planar) monomer has the carbonyl (C O) groups bent out of the ring plane by ∼10°. Key: charcoal – carbon; red – oxygen; white – hydrogen; hydrogen bonds – blue dashed.
