A phthalazine-based two-in-one chromogenic receptor for detecting Co2+ and Cu2+ in an aqueous environment†
A new multifunctional and highly selective chemosensor 1 for Co2+ and Cu2+ was designed and synthesized. 1 could simultaneously detect both Co2+ and Cu2+ by changing its color from pale yellow to pink and to orange in a near-perfect aqueous solution. The binding modes of 1 to Co2+ and Cu2+ were determined to be a 2 : 1 complexation stoichiometry through Job's plot, ESI-mass spectrometry analysis and 1H NMR titration. The detection limits (1.5 and 2.1 μM) of 1 for Co2+ and Cu2+ were lower than the DEP guidelines (1.7 μM for Co2+) and the WHO guidelines (31.5 μM for Cu2+) for drinking water. The chemosensor 1 could be used to quantify Co2+ and Cu2+ in water samples. Moreover, 1 could be used as a practical, visible colorimetric test kit for both Co2+ and Cu2+. The sensing mechanisms of Co2+ and Cu2+ by 1 were supported by theoretical calculations.