Visualization of Zn²⁺ ions in live zebrafish using a luminescent iridium(III) chemosensor

A novel luminescent cyclometalated iridium(III) complex-based chemosensor (1) bearing a zinc-specific receptor, tris(2-pyridylmethyl)amine, and the 3-phenyl-1H-pyrazole ligand has been designed and synthesized. Upon the addition of Zn²⁺ ions to a solution of iridium(III) complex 1, a pronounced luminescence color change from blue to green can be observed, which may be attributed to the suppression of photoinduced electron transfer upon complexation of complex 1 with Zn²⁺ ions. The interaction of iridium(III) complex 1 with Zn²⁺ ions was investigated by UV-vis absorption titration, emission titration, and ¹H NMR titration. Furthermore, the iridium(III) complex 1 exhibited good selectivity for Zn ²⁺ over 13 other common metal ions, including K⁺, Ag ⁺, Na⁺, Ni²⁺, Fe³⁺, Hg²⁺, Cd²⁺, Mg²⁺, Ca²⁺, Cu²⁺, Mn ²⁺, Co²⁺, and Pb²⁺ ions. The practical application of the iridium(III) complex 1 in visualizing intracellular Zn ²⁺ distribution in live zebrafish was also demonstrated. © 2014 American Chemical Society.