coupled pH-metric and fluorimetric titrations allowed the determination of the response of the systems as ON-OFFfluorescentsensors for Cu(2+). A correlation between the effective lipophilicity of the ligand and the residual fluorescence (i.e. the fluorescence of the OFF state) was observed, and with the more lipophilic ligand, L3H(2), we obtained a residual fluorescence as low as 8%, with a significant