Hannover 2020 – scientific programme

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MO: Fachverband Molekülphysik

MO 8: MO Poster 2

MO 8.2: Poster

Tuesday, March 10, 2020, 17:00–19:00, Empore Lichthof

Ultrafast photo-ion probing of the ring-opening process in trans-stilbene oxide — •Matthew Scott Robinson, Mario Niebuhr, Fabiano Levar, Dennis Mayer, Jan Metje, and Markus Gühr — Universität Potsdam, Institut für Physik und Astronomie, Karl-Liebknecht-Straße 24/25, 14476 Potsdam-Golm, Germany

We study the ultrafast photo-induced ring-opening processes of trans-stilbene oxide through UV/UV pump-probe time-of-flight experiments with photoion probing and synchrotron-based vacuum ultraviolet ionisation studies, before comparing these results to predictions derived from Woodward-Hoffmann rules.[1]

We fit two major time-dependent features to the parent ion; one sub-90 fs and another of ~260 fs, which match well to theory.[2] We attribute these constants to the primary ring-opening process, likely proceeding via a non-concerted pathway, starting with a sub-90 fs dissociation of the C-C bond in the oxirane ring, followed by the rotation of the phenyl groups to produce the ring-open carbonyl ylide 260 fs after excitation.

We also investigate the appearance of fragment ions, with one in particular (deprotonated diphenylmethane) suggesting an alternative ring-opening pathway not predicted by Woodward-Hoffmann rules, in which dissociation of one of the C-O bonds of the oxirane ring initiates a 1,2-migration of a phenyl group to produce diphenylmethane.

1. Woodward & Hoffmann, Angew. Chemie 81, 797-870 (1969).

2. Friedrichs & Frank, Chem. - A Eur. J. 15, 10825-10829 (2009).