Giant macrocycles composed of thiophene, acetylene, and ethylene building blocks

Kazumi Nakao, Masayuki Nishimura, Tomoya Tamachi, Yoshiyuki Kuwatani, Hitoshi Miyasaka, Tohru Nishinaga, Masahiko Iyoda

Research output: Contribution to journalArticlepeer-review

148 Citations (Scopus)

Abstract

Fully conjugated giant macrocyclic oligothiophenes with 60π, 90π, 120π, 150π, and 180π frames (1, 2, 3, 4 and 5) have been designed, and their butyl-substituted derivatives (1a, 2a, 3a, 4a, and 5a) have been synthesized using modified Sonogashira and McMurry coupling reactions as key steps. The 60-180π systems 1-5 are circular with 1.8-6 nm inner cavities and 3.3-7.5 nm outside molecular diameters. Compound 1a containing ten 3,4-dibutyl-2,5-thienylene, eight ethynylene, and two vinylene units has been converted into macrocyclic oligo(3,4-dibutyl-2,5-thienylene-ethynylene) 6a using bromination/dehydrobromination procedure. Giant macrocycles 1a-6a exhibit a red shift of their absorption spectra and a fairly strong fluorescence with a large Stokes shift as compared to a linear conjugated counterpart having five thiophene rings. Compounds 1a-6a exhibit multistep reversible redox behaviors with fairly low first oxidation potentials, reflecting their cyclic conjugation. Furthermore, chemical oxidation of 1a-6a with FeCl3 shows drastic changes of spectroscopic properties due to intramolecular and intermolecular π-π interactions. Doping of 1a-3a with iodine forms semiconductor due to its π-donor properties and π-π stacking ability. X-ray analysis of 1a confirmed a round, planar structure with nanoscale inner cavity, and revealed host ability for alkanes and unique packing structure. Interestingly, 2a and 3a self-aggregate in the solid state to form "molecular wires," which are about 200 nm thick and more than 1 mm long. The internal structures of fibrous aggregates have been investigated by optical microscope, scanning electron microscopy, atomic force microscopy, and X-ray diffraction analyses.

Original languageEnglish
Pages (from-to)16740-16747
Number of pages8
JournalJournal of the American Chemical Society
Volume128
Issue number51
DOIs
Publication statusPublished - 2006 Dec 27

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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