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MO: Fachverband Molekülphysik

MO 21: Photochemie 2

MO 21.4: Talk

Thursday, March 5, 2009, 14:45–15:00, VMP 6 HS-G

Characterization of the Conical Intersection Seam for Trifluoromethyl-Pyrrolylfulgid, a Highly Substituted Cyclohexadiene Derivative — •Artur Nenov and Regina de Vivie-Riedle — Department Chemie und Pharmazie, Ludwig-Maximilians-Universität München, Butenandt-Str. 11, 81377, München, Germany

Conical intersections of low energy form seams important for photochemical reactions. Different techniques have been developed to determine critical points on these seams [1]. However, quantum dynamical calculations have shown that these points are often not reached during wave packet propagation. A prominent example is the photoinduced isomerisation of cyclohexadiene (CHD) to cZc-hexatriene (HT) [2]. By using linear interpolation methods and constrained gradient difference optimization, we were able to connect three CoIns of minimum energy via a low energy path, thus extending the seam described in previous papers [3]. We applied this approach on trifluoromethyl-pyrrolylfulgid, a highly substituted CHD derivative. The identified conical seam involves molecular motions similar as in case of CHD, however shifted in coordinate space due to electronic and steric effects of the substituents. From the topology of the optimized seams we could locate regions on the PES that lead predominantly either to the educt or to the product state and thus significantly influence the course of the reaction.

[1] M.J. Bearpark, M.A. Robb, Chem. Phys. Lett. 223 (1994) 169

[2] A. Hofmann and R. de Vivie-Riedle, Chem. Phys. Lett. 346 (2001) 299

[3] M. Garavelli, W. Fuss J. Phys. Chem. A 105 (2001) 4458