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The anti-aromatic dianion and aromatic tetraanion of [18]annulene

Journal Article · · Nature Chemistry
 [1];  [2];  [3];  [2];  [2];  [3]
  1. State Univ. of New York (SUNY), Albany, NY (United States); Univ. of Oxford (United Kingdom)
  2. State Univ. of New York (SUNY), Albany, NY (United States)
  3. Univ. of Oxford (United Kingdom)
+ Show Author Affiliations
π-Conjugated macrocycles behave differently from analogous linear chains because their electronic wavefunctions resemble a quantum particle on a ring, leading to aromaticity or anti-aromaticity. [18]Annulene, (CH)18, is the archetypal non-benzenoid aromatic hydrocarbon. Molecules with circuits of 4n+2 π electrons, such as [18]annulene (n=4), are aromatic, with enhanced stability and diatropic ring currents (magnetic shielding inside the ring), whereas those with 4n π electrons, such as the dianion of [18]annulene, are expected to be anti-aromatic and exhibit the opposite behaviour. Here we use 1H NMR spectroscopy to re-evaluate the structure of the [18]annulene dianion. We also show that it can be reduced further to an aromatic tetraanion, which has the same shape as the dianion. The crystal structure of the tetraanion lithium salt confirms its geometry and reveals a metallocene-like sandwich, with five Li+ cations intercalated between two [18]annulene tetraanions. We also report a heteroleptic sandwich, with [18]annulene and corannulene tetraanion decks.
Research Organization:
Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Organization:
USDOE Office of Science (SC)
Grant/Contract Number:
AC02-06CH11357
OSTI ID:
2470231
Journal Information:
Nature Chemistry, Journal Name: Nature Chemistry Journal Issue: 6 Vol. 16; ISSN 1755-4330
Publisher:
Nature Publishing GroupCopyright Statement
Country of Publication:
United States
Language:
English

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Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Chemical bonding
Density functional theory
Structure elucidation