Among a large series of monoanions, dihydrogen phosphate gives an anion-specific reaction with Zn^II-salphen complexes based on a proton transfer to the chromophore. Detailed NMR and UV/Vis spectroscopic studies and mass spectrometric analyses point to initial activation of the phosphate anion upon coordination, followed by protonation of the phenolic positions of a second Zn^II-salphen structure as supported by kinetic investigations. For a bis(Zn^II-salphen) chromophore this process is accompanied by a considerable colour change.