Gas-Phase Synthesis of Coronene through Stepwise Directed Ring Annulation
Shane J. Goettl, Lotefa Binta Tuli, Andrew M. Turner, Yahaira Reyes, A. Hasan Howlader, Stanislaw F. Wnuk, Patrick Hemberger, Alexander M. Mebel, Ralf I. Kaiser
Abstract
Molecular beam experiments together with electronic structure calculations provide the first evidence of a complex network of elementary gas-phase reactions culminating in the bottom-up preparation of the 24π aromatic coronene (C 24 H 12 ) molecule─a representative peri-fused polycyclic aromatic hydrocarbon (PAH) central to the complex chemistry of combustion systems and circumstellar envelopes of carbon stars. The gas-phase synthesis of coronene proceeds via aryl radical-mediated ring annulations through benzo[ e ]pyrene (C 20 H 12 ) and benzo[ ghi ]perylene (C 22 H 12 ) involving armchair-, zigzag-, and arm-zig-edged aromatic intermediates, highlighting the chemical diversity of molecular mass growth processes to polycyclic aromatic hydrocarbons. The isomer-selective identification of five- to six-ringed aromatics culminating with the detection of coronene is accomplished through photoionization and is based upon photoionization efficiency curves along with photoion mass-selected threshold photoelectron spectra, providing a versatile concept of molecular mass growth processes via aromatic and resonantly stabilized free radical intermediates to two-dimensional carbonaceous nanostructures.