Heidelberg 2015 – scientific programme

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MO: Fachverband Molekülphysik

MO 3: Femtosecond Spectroscopy 1

MO 3.6: Talk

Monday, March 23, 2015, 16:00–16:15, PH/HS1

The photoinduced ring closure of an o-acylbenzaldehyde - Intricate kinetics deciphered by femtosecond spectroscopy and quantum chemistry — •Sascha Fröbel, Laura Buschhaus, Torben Villnow, Oliver Weingart, and Peter Gilch — Heinrich-Heine-Universität Düsseldorf, Germany

The photoinduced ring closure of o-acylbenzaldehydes has been under investigation for decades. Nevertheless, the course of the reaction is not yet completely understood. This can be attributed to the fact that it contains multiple ultrafast processes, which heretofore could not be resolved.

We combined femtosecond absorption techniques and stimulated Raman spectroscopy (FSRS) with quantum chemical computations to study the photoreaction of o-acetylbenzaldehyde in acetonitrile [1]. It turned out that the photochemistry and -physics of this compound are rather complex, involving at least five kinetic processes within the first two nanoseconds after excitation. By FSRS, one of these processes was identified as an intramolecular hydrogen transfer yielding a ketene intermediate. Afterwards the photoproduct, 3-methylphthalide, is formed via an additional intermediate with a lifetime of more than 100 microseconds.

[1]S. Fröbel et al., Phys.Chem.Chem.Phys. 2015, 17, 376-386.