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Aromaticity and Möbius antiaromaticity in monocyclic [11]annulenium cations
1Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts 02115, USA. p.warner@neu.edu
The Journal of Organic Chemistry
|December 2, 2006
Summary
This study computationally explores novel [11]annulenium cations, identifying several aromatic, nonaromatic, and Möbius antiaromatic structures. These findings suggest potential synthetic targets for further investigation.
Area of Science:
- Computational Chemistry
- Organic Chemistry
- Theoretical Chemistry
Background:
- Monocyclic [11]annulenium cations are theoretically interesting but experimentally uncharacterized.
- Previous studies relied heavily on Density Functional Theory (DFT) methods.
Purpose of the Study:
- To computationally investigate the structures and (anti)aromatic properties of unknown monocyclic [11]annulenium cations.
- To explore derivatives formed by fusing three-membered rings (3MRs) to an 11-membered ring (11MR).
Main Methods:
- Density Functional Theory (DFT) calculations.
- Coupled Cluster with Singles and Doubles and Perturbative Triples (CCSD(T)) validation.
- Analysis of magnetic data for ground singlet and vertical triplet states.
- Consideration of aromatic stabilization energies (ASE).
Main Results:
- Six minima for [11]annulenium cations were located, exhibiting varying degrees of aromaticity (aromatic, modestly aromatic, nonaromatic, Möbius antiaromatic).
- Fusion of 3MRs to the 11MR yielded planar, all-cis-[11]annulenium ion derivatives and Möbius antiaromatic species.
- Optimized triplet states revealed additional Möbius aromatic systems.
Conclusions:
- The study provides a comprehensive computational analysis of [11]annulenium cations and their derivatives.
- Several identified structures are proposed as feasible synthetic targets.
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