A macrocyclic oligofuran: synthesis, solid state structure and electronic properties

We report the first pi-conjugated macrocyclic system with an oligofuran backbone. The calculated HOMO-LUMO gap is similar to that of the corresponding linear polymer, indicating a remarkable electron delocalization. The X-ray structure reveals a planar conformation, in contrast to the twisted conformation of macrocyclic oligothiophenes. The intermolecular pi-pi stacking distance is extremely small (3.17 angstrom), indicating very strong interactions. The macrocycle forms large pi-aggregates in solution and shows a tendency toward highly ordered multilayer adsorption at the solid-liquid interface. The face-on orientation of molecules explains the higher hole mobility observed in the out-of-plane direction.