Syntheses, structures, and supramolecular properties of giant π-expanded macrocyclic oligothiophenes

Fully conjugated pi-expanded macrocyclic oligothiophenes with 60 pi-, 90 pi-, 120 pi-, 150 pi-, and 180 pi-electron systems (1-5) were synthesized using modified McMurry coupling reaction as a key step. Compound 1 was converted into macrocyclic oligo(2,5-thienylene-ethynylene) 6 using bromination-dehydrobromination procedure. X-ray analysis of I revealed a unique molecular and packing structure, reflecting a round, planar shape with nanoscale inner cavity. Interestingly, 2 and 3 self-aggregate in the solid state to form nanowires. The structure of fibrous aggregates was established by scanning electron microscopic and atomic force microscopic analyses. Compounds 1-6 exhibit multi-step reversible redox behavior with fairly low first oxidation potentials, reflecting their cyclic conjugation. Doping of 1-3 with iodine gives semiconductors owing to their pi-donor properties and pi-pi stacking ability. (c) 2007 Wiley Periodicals, Inc.