Gas-phase preparation of azulene (C<sub>10</sub>H<sub>8</sub>) and naphthalene (C<sub>10</sub>H<sub>8</sub>) <i>via</i> the reaction of the resonantly stabilized fulvenallenyl (C<sub>7</sub>H<sub>5</sub>˙) and propargyl (C<sub>3</sub>H<sub>3</sub>˙) radicals
Wang Li, Jiuzhong Yang, Long Zhao, David E. Couch, Myrsini San Marchi, Nils Hansen, Alexander N. Morozov, Alexander M. Mebel, Ralf I. Kaiser
Abstract
) molecule, the simplest polycyclic aromatic hydrocarbon carrying an adjacent five- and seven-membered ring, have been of fundamental importance due to the role of azulene - a structural isomer of naphthalene - as an essential molecular building block of saddle-shaped carbonaceous nanostructures such as curved nanographenes and nanoribbons. Here, we report on the very first gas phase preparation of azulene by probing the gas-phase reaction between two resonantly stabilized radicals, fulvenallenyl and propargyl , in a molecular beam through isomer-resolved vacuum ultraviolet photoionization mass spectrometry. Augmented by electronic structure calculations, the novel Fulvenallenyl Addition Cyclization Aromatization (FACA) reaction mechanism affords a versatile concept for introducing the azulene moiety into polycyclic aromatic systems thus facilitating an understanding of barrierless molecular mass growth processes of saddle-shaped aromatics and eventually carbonaceous nanoparticles (soot, interstellar grains) in our universe.