Two Zn(II)-dinuclear systems based on polyamino-phenolic ligands are investigated as metallo-receptors for phosphates; they are able to discriminate phosphate (Pi) from pyrophosphate (PPi) and vice versa in aqueous solution. The fluorescence of one of these systems is affected by the presence of Pi and PPi at physiological pH; the presence of Pi quenches while PPi enhances the emission. Two simple signaling systems for phosphates based on the displacement method were prepared.