Theoretical investigation on proton-induced intramolecular charge transfer of a D-π-A dye for a pH molecular switch

► The S0 and S1 states of the neutral and protonated DCDHC are calculated. ► The experimental absorption and emission spectra are reproduced. ► Proton-induced intramolecular charge transfer occurs upon adding protons. ► The N atom of the amino group should be the major site to accept a proton.