Mainz 2017 – scientific programme

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MO: Fachverband Molekülphysik

MO 1: Photochemistry

MO 1.5: Talk

Monday, March 6, 2017, 15:45–16:00, N 6

Dynamical studies on the photodissociation of diphenylmethyl bromide — •Franziska Schüppel, Matthias K. Roos, and Regina de Vivie-Riedle — Department Chemie, Ludwig-Maximilians-Universität München

Carboradicals and -cations are key intermediates for many chemical reactions. They may be generated by UV-laser excitation of carbohalide compounds such as diphenylmethyl bromide. Here, a local π−π^* excitation occurs, followed by the C-Br bond cleavage leading to radical or ion pairs within a femtosecond timescale.

We use both, quantum dynamical and semiclassical on-the-fly dynamical methods to simulate the reaction. In both approaches we employ an ONIOM two-layer method with CASSCF as high level method. In the quantum dynamics we take the solvent environment into account using the Dynamic Continuum ansatz [1] developed in our group.

We verify for both simulations the decisive role of two consecutive conical intersections for the product splitting, like we recently showed [2] for chlorine as leaving group. Nonetheless, we report remarkable differences compared to the chlorine case and we especially discuss the role of the pyramidalization of the central carbon atom. We evaluate product ratio and delay times for both approaches and compare them with experimental results.

[1] S. Thallmair et al., J. Phys. Chem. Lett. 5 (2014), 3480-3485.

[2] S. Thallmair et al., Struct. Dyn. 3 (2016), 043205.