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Published on: April 19, 2019
The bisketene radical cation and its formation by oxidative ring-opening of cyclobutenedione
Krzysztof Piech1, Thomas Bally, Annette D Allen
1Department of Chemistry, University of Fribourg, CH-1700 Fribourg, Switzerland.
Abstract:
Parent cyclobutenedione 1 was photolyzed and ionized in an Ar matrix at 10K. The bisketene 2 that results in both cases (in the form of its radical cation after ionization) was characterized by its IR spectrum and by high-level quantum chemical calculations. Experiment and theory show that the neutral bisketene has only a single conformation where the two ketene moieties are nearly perpendicular, whereas the radical cation is present in two stable planar conformations. The mechanism of the ring-opening reaction, both in the neutral and in the radical cation, is discussed on the basis of calculations. In the latter case it is a nonsynchronous process that involves an avoided crossing of states.
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