Electron Propagator Theory Approach to the Electron Binding Energies of a Prototypical Photo-Switch Molecular System: Azobenzene

Abstract

The electron binding energies for the trans and cis conformers of azobenzene (AB), a prototypical photoswitch, were investigated by electron propagator theory (EPT). The EPT results are compared with data from photoelectron and electron transmission spectroscopies and complemented by the calculation of the differences between vertical and adiabatic ionization energies and electron affinities of the AB conformers. These differences are discussed in terms of the geometry changes associated with the processes of ionization and electron attachment. The results pointed out a major difference between these processes when we compare trans-AB and cis-AB. For trans-AB, electron attachment leads to a small geometry change, whereas for cis-AB, it is the ionized structure that keeps some similarity with the neutral species. We emphasize the interest of the present results for a better understanding of recent experiments on the dark cis−trans isomerization in different environments, specifically for azobenzenes in interaction with gold nanoparticles, where the proposed cis−trans isomerization mechanism relies on electron transfer induced isomerization.

Low-Energy Electron Scattering from Pyrrole and Its Isomers

“…Electron affinity values of the possible fragments were obtained with electron propagator theory calculations by using outer valence Green's function and the partial third-order quasiparticle (P3) methods applied at optimized geometries. 68 The optimized geometries of radical fragments were obtained at the unrestricted B3LYP/6-311++G(d,p) level of theory. The obtained IR values under these optimized geometries are found to be reliable.…”

Solar–Thermal Fuels and the Role of Carbon Nanomaterials: A Perspective with Emphasis on the Azobenzene System

“…Proposed pathway for a dark cis – trans isomerization for the AB system in interaction with AuNPs. Reproduced with permission from ref .…”

“…Although this property could be recovered through molecular engineering, by physically distancing the azo bridge from the Au surface, the strategy was not universally successful . Several studies suggested that the isomerization rate, in particular, the cis reconversion to trans , is affected by electron transfer (see Figure ) from Au nanoparticles (AuNPs) to the molecule. − …”

Oriented External Electric Field Tuning of Unsubstituted Azoheteroarene Thermal Isomerization Half-Lives

“…Molecular switches are defined as molecular systems that can reversibly shift between at least two different states . Azobenzene (AB) has been studied extensively as a prototypical photoswitch molecule, − and its applications range from memory devices , to molecular motors and actuators. − AB exhibits a photoinduced isomerization process, converting from its trans isomer to cis isomer, after which either a thermal relaxation or absorption of another photon can allow reversion back to the trans isomer. Although AB-based photoswitches can be switched through photon absorption alone, in practice, incomplete photoswitching occurs due to overlapping absorbance of the two isomers .…”