Phosphorescent Iridium(III) Complex with an N^∧O Ligand as a Hg²⁺-Selective Chemodosimeter and Logic Gate

Phosphorescent iridium(III) complexes have been attracting increasing attention in applications as luminescent chemosensors. However, no instance of an iridium(III) complex being used as a molecular logic gate has hitherto been reported. In the present study, two iridium(III) complexes, [Ir(ppy)₂(PBT)] and [Ir(ppy)₂(PBO)], have been synthesized (PBT, 2-(2-Hydroxyphenyl)-benzothiazole; PBO, 2-(2-hydroxyphenyl)-benzoxazole), and their chemical structures have been characterized by single-crystal X-ray analysis. Theoretical calculations and detailed studies of the photophysical and electrochemical properties of these two complexes have shown that the N^∧O ligands dominate their luminescence emission properties. Moreover, [Ir(ppy)₂(PBT)], containing a sulfur atom in the N^∧O ligand, can serve as a highly selective chemodosimeter for Hg²⁺ with ratiometric and naked-eye detection, which is associated with the dissociation of the N^∧O ligand PBT from the complex. Furthermore, complex [Ir(ppy)₂(PBT)] has been further developed as an AND and INHIBIT logic gate with Hg²⁺ and histidine as inputs.