Quantum chemistry and surface hopping dynamics of azobenzenes : free and constrained models This cumulative doctoral dissertation based on three publications is devoted to the investigation of several aspects of azobenzene molecular switches with the aid of computational chemistry. In the first paper the isomerization rates of a thermal cis → trans isomerization of azobenzenes for species formed upon an integer electron transfer i.e. with added or removed electron are calculated from Eyring’s transition state theory and activation energy barriers computed by means of density functional theory. The obtained results are discussed in connection with an experimental study of the thermal cis → trans isomerization of azobenzene derivatives in the presence of gold nanoparticles which is demonstrated to be greatly accelerated in comparison to the same isomerization reaction in the absence of nanoparticles. The second paper is concerned with electronically excited states of (i) dimers composed of two photoswitchable units placed closely side by side as well as (ii) monomers and dimers adsorbed on a silicon cluster. ...