Switching Off Aromaticity

Using a laser pulse, chemists have stripped benzene of its aromaticity, generating two different nonaromatic states of the molecule (J. Am. Chem. Soc., DOI: 10.1021/ja206193t). The approach could help chemists to further probe bonding and electronic structure in molecules. Inga S. Ulusoy and Mathias Nest, of Germany’s Technical University of Munich, used quantum optimal control theory to optimize the laser pulse they needed for switching between aromatic and nonaromatic states. By controlling the electron dynamics, the researchers were able to generate the Kekulé structures for benzene, with alternating single and double bonds, as well as an ionic state, in which the bond orders are the same but electronic charge accumulates on every other carbon.