In particular, the S1 1 (n-π*) and S2 1 (π-π*) states identified at Franck-Condon were optimized at CASSCF level, reaching the respective minima whose diabatic nature was confirmed by analyzing the respective molecular orbitals. Starting from these structures, relaxed scans along the dihedral angle optimizing both S1 and S2 states were performed freezing the dihedral at the desired value and relaxing along all the other coordinates. In addition, the same procedure for the other compounds 6a and 6d was also performed. In case of 6a, the MEP from FC yields directly to a crossing region and not scan was needed for this coordinate.