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DOI: 10.1055/s-2008-1042849
Metalation-Triggered Möbius Aromaticity
Contributor(s):Timothy M. Swager, Jose M. LobezYonsei 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
Publication History
Publication Date:
19 March 2008 (online)
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.