Besides the geometries in solvent phase (acetonitrile and water), we computed the S0 state geometries in gas phase of fd-DMAPAN and tw-HDMAPAN to estimate the 𝑝𝐾 𝑎 for HDMAPAN, following the protocol by Jacquemin and co-workers based on the Born-Haber thermodynamic cycle. In agreement to their procedure, the Gibbs free energies of solvation were obtained using the Gibbs free energy of the gas phase geometry and the total energy of a single point calculation in solvent phase (SMD) using the gas phase geometry. Thus, using water as the solvent and the optimized structures with symmetry, we found the 𝑝𝐾 𝑎 = 3.0 for HDMAPAN. This 𝑝𝐾 𝑎 is 0.7 units above the 𝑝𝐾 𝑎 of the strong photoacid APTS, which also has its acidic proton bonded to an amine group attached to an aromatic ring system (pyrene).