Methodological keys for accurate pKa* simulations.

Photoacids have a stronger propensity to give protons in their excited state than in their ground state which is a key feature for developing new material properties. Experimentally the determination of the excited state dissociation constants (pKa*) remains challenging as the lifetime of the photoacid, in its excited state, is too small. The present article establishes several protocols using the latest developments of the PCM-TD-DFT formalism e.g. both the corrected linear response (cLR) and state specific (SS) approaches. Equilibrium (eq) and non-equilibrium (neq) limits of the implicit solvent have been compared and we highlight that the SS-TD-DFT formalism provides figures in good agreement with experimental data once the eq limit is combined with the Born-Haber cycle or when the neq is used with the Föster cycle using absorption rather than emission transition energies.