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Synfacts 2008(4): 0363-0363  
DOI: 10.1055/s-2008-1042849
Synthesis of Materials and Unnatural Products
© Georg Thieme Verlag Stuttgart · New York

Metalation-Triggered Möbius Aromaticity

Contributor(s):Timothy M. Swager, Jose M. Lobez
Y. Tanaka, S. Saito, S. Mori, N. Aratani, H. Shinokubo, N. Shibata, Y. Higuchi, Z. S. Yoon, K. S. Kim, S. B. Noh, J. K. Park, D. Kim*, A. Osuka*
Yonsei University, Seoul, Korea; Kyoto University, University of Hyogo and The RIKEN SPring-8 Center, Hyogo, Japan
Metalation of Expanded Porphyrins: A Chemical Trigger Used To Produce Molecular Twisting and Möbius Aromaticity
Angew. Chem. Int. Ed.  2008,  47:  681-684  
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Publication History

Publication Date:
19 March 2008 (online)

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Key words

Möbius aromaticity - expanded porphyrins - metalation templating - two-photon absorption

Significance

A new way to achieve complexes that exhibit Möbius aromaticity is described. Conjugated oligopyrrolic macrocycles (also known as expanded porphyrins) were locked into a twisted Möbius strip conformation using group 10 metals. Experimental and numerical studies reveal compounds 3, 5, and 7-9 as conformationally locked Möbius aromatic molecules.

Comment

Structures and aromaticity were confirmed via XRD (2, 3, 5), 1H-NMR and UV/Vis. Significantly negative values of calculated NICS (Nucleus-Independent Chemical Shift) supported Möbius-type aromaticity for 3, 5, and 7 -9. A new method for the quantitative analysis of aromaticity based on the measurement of the TPA (two-photon absorption) cross-section (σ(2)) by the open-aperture Z-scan method showed consistent results.

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