Singly and Doubly Twisted [36]Annulenes: Synthesis and Calculations

• Published in: Chemistry : a European journal Vol. 16; no. 26; pp. 7767 - 7772
• Main Authors: Mohebbi, Ali Reza, Mucke, Eva-Katrin, Schaller, Gaston R., Köhler, Felix, Sönnichsen, Frank D., Ernst, Ludger, Näther, Christian, Herges, Rainer
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 12.07.2010; WILEY‐VCH Verlag; Wiley; Wiley Subscription Services, Inc
• Subjects: annulenes; Aromaticity; Chemistry; Chemistry, Multidisciplinary; Crystallization; density functional calculations; Mathematical analysis; NMR spectroscopy; Physical Sciences; Science & Technology; Solvents; Synthesis; Topology; twisted conformations; X-rays; density functional calculations; MOBIUS AROMATICITY; LINKING NUMBER; SELF-LINKING; CHEMISTRY; WRITHE; annulenes; NMR spectroscopy; RULES; OLIGOMERS; aromaticity; twisted conformations
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201000277

A cyclophane with a [36]annulene periphery, including four anthrylene and two phenylene units, was synthesized in a four‐step sequence using a McMurry cyclization. Upon crystallization from different solvents, four different conformations were determined by X‐ray structure analysis. Two conformations exhibit a double twist (Hückel topology) and two structures include a single twist (Möbius topology). By using DFT calculations a conformation with a triple twist (Möbius) was located. However, our calculations and the NMR spectroscopy data do not provide evidence for aromaticity (for Möbius structures) or antiaromaticity (for Hückel structures). Do the twist! Möbius and Hückel conformations (single‐ and double‐twisted) were crystallized from a solution of a cyclophane with a [36]annulene periphery in different solvents (see figure). All new structures were clearly identified by X‐ray analysis and confirmed by DFT calculations. An energetically favorable triple‐twisted conformation of the annulene was also located by using DFT calculations.