Ultralong C-C bonds in hexaphenylethane derivatives

Takanori Suzuki, Takashi Takeda, Hidetoshi Kawai, Kenshu Fujiwara

Research output: Contribution to journalArticlepeer-review

32 Citations (Scopus)


The longer C-C bond than the standard (1.54 Å) is so weakened that it is cleaved easily, as found in the parent hexaphenylethane (HPE). However, the compounds with an ultralong C-C bond (1.75 Å) can be isolated as stable solids when the bond-dissociated species does not undergo any reactions other than bond reformation. This is the central point in designing the highly strained HPEs, which were obtained by two-electron reduction of the corresponding dications. Steric repulsion of "front strain" is the major factor to expand the central C-C bond of HPEs. During the detailed examination of the ultralong C-C bond, the authors discovered the intriguing phenomenon of "expandability": the C-C bond length can be altered over a wide range by applying only a small amount of energy (1 kcal mol -1) supplied by crystal packing force. This observation indicates that the much longer C-C bond than the shortest nonbonded contact (1.80 Å) will be realized under the rational molecular design concept.

Original languageEnglish
Pages (from-to)547-553
Number of pages7
JournalPure and Applied Chemistry
Issue number3
Publication statusPublished - 2008 Mar
Externally publishedYes


  • Covalent bonds
  • Hexaphenylethanes
  • Long bonds
  • Redox system
  • Strained molecules
  • X-ray structures

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)


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