title: Dynamics of Azobenzene Dimer Photoisomerization: Electronic and Steric Effects.
abstract: While azobenzenes readily photoswitch in solution, their photoisomerization in densely packed self-assembled monolayers (SAMs) can be suppressed. Reasons for this can be steric hindrance and/or electronic quenching, e.g., by exciton coupling. We address these possibilities by means of nonadiabatic molecular dynamics with trajectory surface hopping calculations, investigating the trans → cis isomerization of azobenzene after excitation into the ππ* absorption band. We consider a free monomer, an isolated dimer and a dimer embedded in a SAM-like environment of additional azobenzene molecules, imitating in this way the gradual transition from an unconstrained over an electronically coupled to an electronically coupled and sterically hindered, molecular switch. Our simulations reveal that in comparison to the single molecule the quantum yield of the trans → cis photoisomerization is similar for the isolated dimer, but greatly reduced in the sterically constrained situation. Other implications of dimerization and steric constraints are also discussed.
authors.affiliation: Theoretical Chemistry, Institute of Chemistry, University of Potsdam , Karl-Liebknecht-Straße 24-25, 14476 Potsdam, Germany.
authors.forename: Evgenii
authors.initials: E
authors.lastname: Titov
authors.affiliation: Department of Chemistry and Industrial Chemistry, University of Pisa , via Moruzzi 13, 56124 Pisa, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Granucci
authors.affiliation: Theoretical Chemistry, Institute of Chemistry, University of Potsdam , Karl-Liebknecht-Straße 24-25, 14476 Potsdam, Germany.
authors.forename: Jan Philipp
authors.initials: JP
authors.lastname: Götze
authors.affiliation: Department of Chemistry and Industrial Chemistry, University of Pisa , via Moruzzi 13, 56124 Pisa, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Persico
authors.affiliation: Theoretical Chemistry, Institute of Chemistry, University of Potsdam , Karl-Liebknecht-Straße 24-25, 14476 Potsdam, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Saalfrank