Over the last decades, progress in experimental techniques combiend with theoretical simulations has given access to studying and controlling the photochemical reactivity of large molecular systems with numerous technological applications. For example, Aminobenzonitrile-like molecules, where different fluorescent patterns are observed, depending of the solvent or its substituents. Such properties are crucial in the field of organic materials to understand and design fluorescent markers or photoswitches.

One major challenge in theoretical chemistry conceern the study of photochemical processes of large molecules (several tens of modes), where conical intersections (CI) play a major role by transferring population between electronic states. This requires the calculation of more than one electronic states and the non-adiabatic coupling between them, the development of analytical quantum chemistry models implemented in the PAnDA program develop by Perveaux et al., and the use of modern quantum dynamics simulation methods such as the multilayer version of MCTDH (ML-MCTDH) . 

This work is focusses on the Aminobenzonitrile charge transfer. In this system, the second excited state (S2) absorbs a UV photon, and CU's between S2 an S1 deactive the system to S1. Experimentally, one fluorescence band from a local excitation (LE) of S1 is observed in gas phase and in solvent (independently of its polarity). A Cs pathway is already know. Nevertheless, we have found a new C2v pathway. Both are complementary and in competition during the photoinduced process. 

The Cs pathway is along the out-of-plane benzene deformation. The Cs-CI is linked to the formation of LE. The twisted (C-NH2 torsion) ICT (TICT) minimum is reached when the wave packet is developed along the torsion mode once on the seam.

The C2v pathway is along the in-plane quinoidic deformation. This motion drives the system to a sloped C2V-CI leading to the formation of LE. One should expect the C2V pathway to be ore efficient than the Cs one in the gase phase, thus, explaining the single fluorescence band.

In a polar solvent, the ICT state will be strongly stabilised. Therefore, the C2V-CI is closer to FC than in gas phase. Quantum dynmics calculations were performed and confirm the fact that the C2V pathway is very efficient in polar solvent.

The full dimension (39D) potential energy surfaces of the C2V pathway were calculated withint the above procedure in gas phase and polar solvent.