Properties of uncharged water-soluble tetra(ω-methoxypolyethyleneoxy)phthalocyanine free base: Viable switching of the optical response by means of H3O+ ions

► An uncharged water soluble tetra (ω-methoxypolyethyleneoxy)phthalocyanine was characterized. ► Phthalocyanine protonation changes the luminescence output. ► The system can be switched alternating H3O+ and OH− as inputs. ► The read-out procedure is fast and reversible. ► Binary codes are assigned to the high and low luminescent states, respectively.