From branched polyphenylenes to graphite ribbons

Jishan Wu, Lileta Gherghel, Mark D. Watson, Jixue Li, Zhaohui Wang, Christopher D. Simpson, Ute Kolb, Klaus Müllen

Research output: Contribution to journalArticlepeer-review

126 Scopus citations

Abstract

This article presents the synthesis of graphitic nanoribbons (∼1 nm wide), containing extended conjugated all-benzenoid segments. These were obtained by intramolecular oxidative cyclodehydrogenation of soluble branched polyphenylenes 6, which were prepared by repetitive Diels-Alder cycloaddition of 1,4-bis(2,4,5-triphenylcyclopentadienone-3-yl)benzene (1) and diethynylterphenyl (5) in good yield. While insolubility of the obtained graphite ribbons 7 precluded standard spectroscopic structure elucidation, the electronic and vibrational properties were probed by solid-state UV-vis, Raman, and infrared spectroscopy. A wide and unstructured absorption band covering the visible range of the electronic spectrum (λmax ∼ 800 nm) is observed, confirming the highly extended conjugated framework. The structure proof of the ribbon-type polymer is supported by the inclusion of appropriate model compounds. The profile of the visible Raman spectrum of the material is similar to that of a discrete polycyclic aromatic hydrocarbon (PAH) C222H42, characterized by two strong bands (at 1603 and 1322 cm-1), corresponding to the G and D bands of graphite. The obtained graphite ribbons are not linear but rather contain "kinks" due to the structural design of the polyphenylene precursor. High-resolution transmission electron microscopy (HRTEM) images of the graphite ribbons 7 disclose two different domains: one is an ordered graphite layer structure with a layer distance of ca. 3.8 Å, and one is disordered due to the existence of "kinks" in the obtained polymers and/or random stacking of graphite ribbons. Attempts to make linear analogues are so far unsuccessful, emphasizing the critical importance of the geometry of the polyphenylene scaffold to successful oxidative cyclodehydrogenation.

Original languageEnglish
Pages (from-to)7082-7089
Number of pages8
JournalMacromolecules
Volume36
Issue number19
DOIs
StatePublished - Sep 23 2003

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry

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