Dual Aromaticity in Both the Ground and the Excited State

  • Author: ChemistryViews.org
  • Published: 31 March 2019
  • Copyright: Wiley-VCH Verlag GmbH & Co. KGaA
  • Source / Publisher: Journal of the American Chemical Society/ACS Publications
  • Associated Societies: American Chemical Society (ACS), USA
thumbnail image: Dual Aromaticity in Both the Ground and the Excited State

Cyclic compounds with conjugated bonds (such as benzene) are usually aromatic only in the ground state or only in their first excited state. Molecules with so-called adaptive aromaticity, which are aromatic in both of these electronic states, are very rare.

Jun Zhu and colleagues, Xiamen University, China, have found the first example of a compound that has a triplet ground state and shows dual aromaticity in both the lowest triplet and the lowest singlet state: an osmapyridinium with phosphonium substituents (pictured, [Os] = OsCl2(PH3)2). The team performed density functional theory (DFT) calculations of 96 different osmapyridine and osmapyridinium compounds. For the compounds calculated to have a planar structure, the researchers evaluated the aromaticity based on the proposed structure, calculated electronic properties, and heats of hydrogenation.

The team found one compound with adaptive aromaticity and a triplet ground state (pictured) and one compound with adaptive aromaticity and a singlet ground state, which is similar in structure, but has no phosphonium substituent. According to the researchers, such compounds could be useful in photochemistry and molecular magnetism applications.



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