Table presents the excitation energies obtained in the solid state. To assess the impact of using different point charges in the electrostatic embedding with the TD-ωB97XD method, we performed calculations with both CM5 and ESP charges. The energy differences in all cases were smaller than or around 0.1 eV. Given this minor effect, the CASPT2 and CC2 calculations were conducted using only CM5 charges. As observed in solution (Table ), the absorption energies of singlet states calculated with TD-ωB97XD and RI-CC2 in the crystal significantly deviate from those obtained with MS-CASPT2. For both TPA and IPA, TD-ωB97XD tends to overestimate the singlet energies. In contrast, RI-CC2 overestimates the singlet energies for TPA and underestimates them for IPA. However, the TD-ωB97XD and will be discussed below (Section ). These differences from previous works are attributed to the different active spaces employed. Our CASSCF/CASPT2 simulations considered a [14,11] active space (9 π and 2 n orbitals), while the smaller [8,8] Based on this benchmark, we conclude that the MS-CASPT2 method with the selected active space ( [14,11]) reproduces the absorption and emission properties of TPA and IPA well (Table ). In Section , we will present the deactivation pathways connecting the ground state minimum with the optimised minimal energy conical intersections (S 1 -S 0 MECI). These pathways were obtained applying the MS-CASPT2 method, which, apart from the good performance in description of absorption and emission, is suitable for the excited states simulations in the vicinity of the conical intersection, due to multireference character of the wave function.