Multidimensional Potential Energy Surfaces Resolved at the RASPT2 Level for Accurate Photoinduced Isomerization Dynamics of Azobenzene

Abstract

We have used state-of-the-art ab initio RASPT2 computations using a 16 orbitals, 18 electrons active space to produce an extended three dimensional map of the potential energy surfaces (PESs) of the ground and first nπ * excited state of azobenzene along CNNC torsion and the two CNN bending angles, which are the most relevant coordinates for the trans-cis photoisomerization process. Through comparison with fully unconstrained optimizations performed at the same level of theory, we show that the three selected coordinates suffice to correctly describe the photoisomerization mechanism and the S 1-S 0 crossing seam. We also provide a map of the non-adiabatic coupling between the two states in the region where they get closer in energy. Eventually, we show that treating the two CNN bending angles as independent coordinates is fundamental to break the symmetry and couple the two electronic states. The accuracy of the S 0 and S 1 PESs and couplings was validated with semiclassical dynamics simulations in the reduced space of the scanned coordinates, showing results in good agreement with published full-coordinates dynamics.

Automatic discovery of photoisomerization mechanisms with nanosecond machine learning photodynamics simulations

“…[13][14][15] Aleotti et al have parameterized ad hoc force elds for a 10 ps dynamic simulation of azobenzene. 16 Westermeyr et al have trained multilayer feedforward neural networks (NNs) to enable 1 ns simulation of methylenimmonium cation (CH 2 NH 2 + ) in 59 days. 17 Later, they have extended the application of the NN model in predicting excitedstates electronic properties for other small molecules, such as SO 2 and CSH 2 employing a deep continuous-lter convolutional-layer neural network, SchNet, combined with SHARC.…”

Ultrafast Nonadiabatic Photoisomerization Dynamics Mechanism for the UV Photoprotection of Stilbenoids in Grape Skin

“…This interesting trans-cis photoisomerization phenomenon has the similar energy relaxation pathway to previously reported skeleton-like stilbene and azobenzene, confirming the rationality of the PESs constructed by LIIC method. [11,13] It is worth noting that for both cis species of ground state, they can also be photoexcited to excited state and return to their ground state by CI point. This phenomenon indicates that a dynamical balance exists between cis and trans species.…”

Trans-to-cis photoisomerization of cyclocurcumin in different environments rationalized by computational photochemistry

“…As it is evident from sterical considerations, the trans isomer is the thermodynamically favoured one and it is indeed the one present in the natural extract. Compounds presenting isomerizable double bonds within rather extended pconjugated backbones, such as carotenoids and retinal, [26][27][28][29][30][31][32] or azobenzene [33][34][35] and stilbene [36][37][38] are regarded as paradigmatic molecular photoswitches, 39,40 i.e. compounds able to undergo photoisomerization after the absorption of visible light.…”