Chair of Theoretical Chemistry
Institute of Chemistry
University of Potsdam, Germany

“Molecular Switches:From Structure to Kinetics and Dynamics”

Hosted by Professor Tamar Seideman

Tech K140

In this contribution, the structure, kinetics, and dynamics of molecular switches, “free” or adsorbed at surfaces, are investigated by quantum mechanical modelling.
All switches considered are of a generalized, e.g. multidimensional, double-minimum type describing processes such as cis-trans isomerization or conformational switching, driven by light, tunneling electrons, or thermally.
In the first part of the presentation the electronic and geometric structure of molecular switches is addressed with the help of quantum chemical methods. Stable structures are elucidated, optical spectra are determined, and rate constants for thermal switching are obtained by Eyring transition state theory. The “tuning” of optical molecular switches, which show photochromic behaviour and thermal stability at the same time, is attempted, notably for azobenzenes, by substitution and electronic decoupling strategies.
In a second part we emphasize the dynamics of the switching process, in particular for molecules at surfaces. An example is COD:Si(100) (COD=cylco-octadien), for which inelastic-electron-tunneling (IET) induced biconfomational switching is modelled with the help of open-system density matrix theory. Another example is the photochemical switching of azobenzenes in constrained geometries, namely tert-butyl-azobenzene (TBA) on gold, for which direct photochemical channels are investigated with the help of surface hopping “dynamics on the fly”.