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Abstract In this work we report the synthesis, structure, and electronic properties of carbon‐rich compounds dehydrobiphenyleno[12]annulenes (DBP[12]As) comprising antiaromatic four‐membered rings (4MR) and 12‐membered ring (12MR). Ultraviolet–visible absorption spectra and electrochemical behaviors of DBP[12]As confirmed their relatively narrow highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gap values and high HOMO energy levels, which were supported by density functional theory simulations. Parent DBP[12]A adopts a slipped herringbone structure in a crystalline state, with the molecules forming 1D stacks via π–π interactions. The experimentally derived bond lengths, bonding analyses using the Wiberg bond indices, and localized orbital locator calculation support a stronger double bond character for the 12MR bonds than the 4MR bonds in the inner six‐membered ring. The chemical shifts of hydrogens in1H NMR spectra, as well as magnetically induced ring current analyses using quantum chemical calculations, indicate that the 4MRs have stronger antiaromatic character than the 12MR. The present information is useful for a fundamental understanding of carbon‐rich compounds with different antiaromatic units as well as designing novel molecules with unique electronic properties.
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Three-dimensional aromaticity in an antiaromatic cyclophane
Abstract Understanding of interactions among molecules is essential to elucidate the binding of pharmaceuticals on receptors, the mechanism of protein folding and self-assembling of organic molecules. While interactions between two aromatic molecules have been examined extensively, little is known about the interactions between two antiaromatic molecules. Theoretical investigations have predicted that antiaromatic molecules should be stabilized when they stack with each other by attractive intermolecular interactions. Here, we report the synthesis of a cyclophane, in which two antiaromatic porphyrin moieties adopt a stacked face-to-face geometry with a distance shorter than the sum of the van der Waals radii of the atoms involved. The aromaticity in this cyclophane has been examined experimentally and theoretically. This cyclophane exhibits three-dimensional spatial current channels between the two subunits, which corroborates the existence of attractive interactions between two antiaromatic π-systems.
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- Award ID(s):
- 1664674
- PAR ID:
- 10154009
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Nature Communications
- Volume:
- 10
- Issue:
- 1
- ISSN:
- 2041-1723
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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