In a recent publication, an extensive computational analysis of DMAC-TRZ set the basis for a few-state model that was carefully validated against spectroscopic properties in solution. Then the same model was exploited to calculate ISC and RISC rate constants, also accounting for environmental effects including dielectric and conformational disorder. In the ground-state equilibrium geometry of DMAC-TRZ, the DMAC and TRZ moieties are mutually orthogonal (Figure ), in line with the crystal structure. In this orthogonal geometry, the S1 and T1 states each have a pure charge transfer (CT) character. In other terms, the HOMO and LUMO have negligible overlap so that the singlettriplet gap is almost closed, with DEST = 0.01 eV. The close similarity between the orbitals involved in S1 and T1 states implies a vanishing SOC, according to El Sayed's rule 6 , as to hinder direct RISC from T1 to S1.