Hexakis(4-(N-butylpyridylium))benzene: a six-electron organic redox system

J Org Chem. 2008 Jan 18;73(2):445-50. doi: 10.1021/jo701944c. Epub 2007 Dec 18.

Abstract

The cobalt-catalyzed cyclotrimerization of bis(4-pyridyl)acetylene affords hexakis(4-pyridyl)benzene in moderate yield. Alkylation with n-butyltriflate gives hexakis(4-(N-butylpyridylium))benzene triflate (1 6+), which can be reduced with Na/Hg in DMF to neutral 10. A single-crystal X-ray diffraction structure reveals that 1 0 has a chair-cyclohexane-like core and a [6]radialene structure. Cyclic voltammetry shows that 1 6+ is reversibly reduced to 1 2+ in one four-electron step and 1 2+ is reversibly reduced to 1 0 in one two-electron step. A reduction by four electrons at one potential is unprecedented for a molecule in which the electrochemically active centers are in electronic communication. The large structural transformation from 1 6+ to 1 0 is responsible for the "potential inversion" in the cyclic voltammetry, and DFT calculations suggest a possible structure for the stable intermediate 1 2+. A comparison is made to the electrochemistry and structural transformations in a previously prepared [4]radialene analogue of 1 0.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Benzene Derivatives / chemical synthesis
  • Benzene Derivatives / chemistry*
  • Crystallography, X-Ray
  • Cyclization
  • Electrochemistry
  • Electrons
  • Models, Chemical
  • Models, Molecular
  • Molecular Structure
  • Oxidation-Reduction
  • Pyridinium Compounds / chemical synthesis
  • Pyridinium Compounds / chemistry*

Substances

  • Benzene Derivatives
  • Pyridinium Compounds
  • hexakis(4-(N-butylpyridylium))benzene