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Chemistry. 2013 Oct 4;19(41):13970-8. doi: 10.1002/chem.201301294. Epub 2013 Aug 26.

Acenaphthylene-fused cyclo[8]pyrroles with intense near-IR-region absorption bands.

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Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577 (Japan), Fax: (+81) 89-927-9615.


An acenaphthylene-fused cyclo[8]pyrrole was synthesized by using an oxidative coupling reaction of the corresponding 2,2'-bipyrrole. Two conformational isomers 1 a and 1 b were isolated, and their molecular structures were elucidated by X-ray crystallographic studies. The less-polar and lower-symmetry 1 b isomer can be converted into the 1 a isomer through a thermal ring flip. Application of the perimeter model developed by Michl to magnetic circular dichroism spectroscopic data and theoretical calculations demonstrate that there is a marked redshift of the near-IR absorption maxima relative to cyclo[8]isoindole because there is a significant stabilization of the LUMO due to the differing effects of a fused ring expansion with acenaphthylene and benzene moieties on the frontier π molecular orbitals.


IR spectroscopy; circular dichroism; density functional calculations; macrocycles; pyrroles


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