Investigation of a putative Mobius aromatic hydrocarbon. The effect of benzannelation on Mobius [4n]annulene aromaticity

Castro C, Chen Z, Wannere C, Jiao H, Karney W, Mauksch M, Puchta R, van Eikema Hommes N, Schleyer P (2005)

Publication Status: Published

Publication Type: Journal article

Publication year: 2005

Journal

Publisher: American Chemical Society

Book Volume: 127

Pages Range: 2425-2432

Journal Issue: 8

DOI: 10.1021/ja0458165

Abstract

The first experimental example of a [4n]annulene derivative with one Mobius twist, 1, was synthesized recently [Ajami, D.; Oeckler, O.; Simon, A.; Herges, R. Nature 2003, 426, 819] and was purported to possess aromatic character. However, critical analysis of the published crystallographic data indicates that the Mobius [16]annulene core of 1 shows large bond alternation (Deltar up to 0.157 Angstrom). Delocalization in this core is inhibited by large dihedral angles, which hinders effective pi overlap. This conclusion is supported by computational results (B3LYP/6-311+G(**)) on 1 and several less benzannelated derivatives, based on geometric (Deltar, Deltar(m), Julg A, HOMA) and magnetic (NICS, magnetic susceptibility exaltation) criteria of aromaticity. That benzannelation results in bond localization in the [16]annulene core is shown by additional computations on benzannelated derivatives of other Mobius aromatic species. Additionally, the aromatic stabilization energy (ASE) of 1 has been reinvestigated using two different procedures. Evaluation of uncorrected ISEII values of just the polyene bridge portion of 1 and its Huckel counterpart suggests that stabilization of 1 relative to its Huckel isomer is confined to the polyene bridge and is not due to a delocalized pi circuit. Furthermore, application of s-cis/s-trans corrections lowers the ISEII value of 1 from 4.0 kcal/mol to 0.6 kcal/mol, suggesting that 1 is nonaromatic.

Authors with CRIS profile

Involved external institutions

University of Georgia (UGA) United States (USA) (US) University of San Francisco (USF) United States (USA) (US)

How to cite

APA:

Castro, C., Chen, Z., Wannere, C., Jiao, H., Karney, W., Mauksch, M.,... Schleyer, P. (2005). Investigation of a putative Mobius aromatic hydrocarbon. The effect of benzannelation on Mobius [4n]annulene aromaticity. Journal of the American Chemical Society, 127(8), 2425-2432. https://dx.doi.org/10.1021/ja0458165

MLA:

Castro, Claire, et al. "Investigation of a putative Mobius aromatic hydrocarbon. The effect of benzannelation on Mobius [4n]annulene aromaticity." Journal of the American Chemical Society 127.8 (2005): 2425-2432.

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