Terpyridine derivatives as turn-on fluorescence chemosensors for the selective and sensitive detection of Zn2+ ions in solution and in live cells

Article abstract of DOI:10.1039/c8pp00186c

A terpyridine based compound L1 was designed and synthesized as an off-on chemosensor for the detection of Zn²⁺. Chemosensor L1 showed excellent selectivity and sensitivity toward Zn²⁺ by exhibiting a large fluorescence enhancement (～51-fold) at 370 nm whereas other competitive metal ions did not show any noticeable change in the emission spectra of chemosensor L1. The chemosensor (L1) was shown to detect Zn²⁺ ions down to 9.76 μM at pH 7.4. However, chemosensor L1 binds Zn²⁺ in a 1:2 ratio (receptor:metal) with an association constant of 1.85 × 10⁴ (R² = 0.993) and this 1:2 stoichiometric fashion is established on the basis of a Job plot and mass spectroscopy. DFT/TD-DFT calculations were carried out to understand the binding nature, coordination features and electronic properties of L1 and the L1-2Zn²⁺ complex. In addition, this turn-on fluorescence probe was effectively used to image intracellular Zn²⁺ ions in cultured MDA-MB-468 cells.