Frenkel exciton photodynamics of self-assembled monolayers of azobiphenyls

We performed computational simulations of the photodynamics of a self-assembled monolayer (SAM) of an azobenzene derivative (azobiphenyl, ABPT) on a gold surface. An excitonic approach was adopted in a semiempirical framework, which allowed us to consider explicitly the electronic degrees of freedom of 12 azobenzene chromophores. The surface hopping scheme was used for nonadiabatic molecular dynamics simulations. According to our results for an all trans-ABPT SAM, the excitation energy transfer between different chromophores, very fast in the pp * manifold, does not occur between np* states. As a consequence, the excitation transfer does not play an important role in the quenching of the azobenzene photoisomerization in the SAM (experimentally observed and reproduced by our calculations) which, instead, has to be attributed to steric effects.

Automated summary

We performed computational simulations on the photodynamics of ABPT SAM on a gold surface. Our results showed that excitation energy transfer between chromophores occurs quickly in the pp* manifold, but not between np* states. As a result, excitation transfer does not play a significant role in the quenching of azobenzene photoisomerization in the SAM, which is instead attributed to steric effects.