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

Fully conjugated π-expanded macrocyclic oligothiophenes with 60π-, 90π-, 120π-, 150π-, and 180π-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 1 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 π-donor properties and π–π stacking ability. © 2007 Wiley Periodicals, Inc. 18:460–466, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20337