Gas-Phase Synthesis of the Elusive Cyclooctatetraenyl Radical (C H ) via Triplet Aromatic Cyclooctatetraene (C H ) and Non-Aromatic Cyclooctatriene (C H ) Intermediates.

The 1,2,4,7-cyclooctatetraenyl radical (C H ) has been synthesized for the very first time via the bimolecular gas-phase reaction of ground-state carbon atoms with 1,3,5-cycloheptatriene (C H ) on the triplet surface under single-collision conditions. The barrier-less route to the cyclic 1,2,4,7-cyclooctatetraenyl radical accesses exotic reaction intermediates on the triplet surface, which cannot be synthesized via classical organic chemistry methods: the triplet non-aromatic 2,4,6-cyclooctatriene (C H ) and the triplet aromatic 1,3,5,7-cyclooctatetraene (C H ). Our approach provides a clean gas-phase synthesis of this hitherto elusive cyclic radical species 1,2,4,7-cyclooctatetraenyl via a single-collision event and opens up a versatile, unconventional path to access this previously largely obscure class of cyclooctatetraenyl radicals, which have been impossible to access through classical synthetic methods.