Reduced Band Gap Dithieno[3,2-<i>b</i>:2‘,3‘-<i>d</i>]pyrroles: New n-Type Organic Materials via Unexpected Reactivity

Direct addition of tetracyanoethylene to N-(p-hexylphenyl)dithieno[3,2-b:2‘,3‘-d]pyrrole yields not only the aromatic mono- and bis-tricyanovinyl-substituted products but also a quinoidal product with dicyanomethylene groups. The analogous reaction with dithieno[3,2-b:2‘,3‘-d]thiophene yields exclusively the aromatic mono-tricyanovinyl product. The aromatic and quinoidal products possess red-shifted absorptions, increased electron affinities, and favorable π-stacking motifs in comparison to the unsubstituted oligomers.