Two Aromatic Rings in One

  • Author: ChemistryViews.org
  • Published: 16 October 2018
  • Copyright: Wiley-VCH Verlag GmbH & Co. KGaA
  • Source / Publisher: Communications Chemistry/Springer Nature Limited
thumbnail image: Two Aromatic Rings in One

Aromatic molecules usually feature a ring of overlapping π-orbitals with 4n+2 electrons (according to the Hückel rule). However, orbitals with other symmetries, such as σ-orbitals, can also form aromatic systems. The existence of "double aromaticity", in which one molecule features both σ- and π-aromaticity, has been predicted theoretically. However, examples of this are rare and no bench-stable doubly aromatic compound had been characterized so far.


Masaichi Saito, Saitama University, Japan, and colleagues have synthesized and isolated the hexakis(phenylselenyl)benzene dication (pictured), which shows double aromaticity. The team synthesized the cation via the two-electron oxidation of its neutral precursor using nitrosonium hexafluoroantimonate ([NO]SbF6). The desired hexafluoroantimonate salt was obtained in a yield of 73 %.


The cation has an inner benzene ring, with six electrons in a ring of π-orbitals (pictured in blue), and an outer selenium six-ring, with ten electrons in a ring of σ-orbitals (pictured in green). Both follow the Hückel rule. X-ray diffraction showed that the distances between adjacent selenium atoms are similar, which would be expected for an aromatic system. NMR measurements provided evidence for an induced σ-ring current in the Se6 group, which also is consistent with aromaticity.


 

 

Article Views: 1437

Sign in Area

Please sign in below

Additional Sign In options

Please note that to comment on an article you must be registered and logged in.
Registration is for free, you may already be registered to receive, e.g., the newsletter. When you register on this website, please ensure you view our terms and conditions. All comments are subject to moderation.

Article Comments - To add a comment please sign in

Bookmark and Share

If you would like to reuse any content, in print or online, from ChemistryViews.org, please contact us first for permission. more


CONNECT:

ChemistryViews.org on Facebook

ChemistryViews.org on Twitter ChemistryViews.org on YouTube ChemistryViews.org on LinkedIn Sign up for our free newsletter


A product of ChemPubSoc Europe (16 European Chemical Societies)and Wiley-VCH