Highly Selective Phthalocyanine−Thymine Conjugate Sensor for Hg2+ Based on Target Induced Aggregation

Here we describe a highly selective and reversible Hg(2+) sensor, tetra-(thymin-1-yl-acetamido)-phthalocyanine Zn(II) (4T-ZnPc), which combined the optical properties of phthalocyanine (Pc) and the specific interaction of Hg(2+) with thymine (T). The novel phthalocyanine-nucleobase conjugate, 4T-ZnPc, shows a typical ultraviolet-visible absorption spectrum with a split Q-band of monomeric Pc in dimethylformamide (DMF)-water (7:3, v/v) solution, as well as strong fluorescence emission. Upon addition of Hg(2+), the formation of T-Hg-T complex induces aggregation of 4T-ZnPc and results in significant decreases of fluorescence intensity and absorption of the Q-band. Furthermore, the sensor molecules, 4T-ZnPc, show excellent selectivity for Hg(2+), and other ions, such as Pb(2+), Co(2+), Ni(2+), Zn(2+), Cd(2+), Mn(2+), Mg(2+), Ca(2+), Na(+), and K(+), have almost no effect on the optical properties of 4T-ZnPc. This kind of sensor based on Pc may be expanded to the detection of other targets by substituting thymines with other ligands or groups that possess molecular recognition ability.