During the period of the project various works were performed. The main photophysical and photochemical decay paths of the molecules were described, performing ground and excited states geometry optimizations, optimizations of conical intersections and singlet-triplet crossing regions, minimum energy path computations and frequencies calculations. Those were performed using the CASSCF and CASPT2 methods, employing different basis sets and active spaces. In order to study their dynamics with the DD-vMCG method, an interface between the electronic structure program Molcas and the dynamics package Quantics was created. Also the DD-vMCG code present in the Quantics program was further develop so to account for the coupling and consequently population transfer between states of different spin multiplicity, as the singlet and triplet states involved in the photoresponse of the mentioned molecules. Using the so implemented Quantics code, the photophysics and photochemistry of the systems were study running quantum dynamics using the vMCG methods in conjunction with the CASSCF and CASPT2 electronic structure theory methods, using both Cartesian coordinates and normal modes.
The main results obtained so far are: characterization of all main photophysical and photochemical decay paths of nitrobenzene, including the characterization of two non-previously reported reactive singlet-triplet crossing regions leading respectively to nitric oxide and epoxide ring formation, and the evaluation of a possible roaming path mediated by a conical intersection between the S1 and S0 states; characterization of the main critical points and decay paths for 1- and 2-nitronaphthalene, comparing the main similarities and differences among the three molecules; improvement of the DD-vMCG code in the Quantics package so to be able to treat both vibronic and spin-orbit couplings; resuls on the timescale and amount of population transfers between both singlet and triplet states after excitation of the S1 state of the three compounds, based on DD-vMCG dynamics.
The results obtained during the project were disseminated through talks and poster in various congresses and conferences. In particular: 4 four talk were delivered, five posters were presented; a total of eleven scientific meetings were attended. The various results obtained on nitrobenzene were published in the Journal of Chemical Theory and Computation (JCTC 2017, 13, 2777-2788).
