A novel cationic iridium(iii) complex with a thiorhodamine-based auxiliary ligand: application for luminescent and colorimetric detection of Hg2+ in an aqueous solution

Abstract

A novel cationic iridium(III) complex [(SRB-DAF)Ir(ppy)₂]PF₆ (SRB-DAF: 2-((5H-cyclopenta[1,2-b:5,4-b′]dipyridin-5-ylidene)amino)-3′,6′-bis(diethylamino)spiro[isoindoline-1,9′-xanthene]-3-thione and ppy: 2-phenylpyridine) with a thiorhodamine-based auxiliary ligand was designed and synthesized. The spirolactam ring of the thiorhodamine group will be opened with the chelation of Hg²⁺ ion, and the iridium(III) complex instantly exhibits remarkable “turn-on” type naked-eye detectable color (λ_max,abs = 567 nm) and phosphorescence (λ_max,em = 587 nm) changes. Hg²⁺ can be detected by this iridium(III) complex with high selectivity and sensitivity in an aqueous solution in the presence of other metal cations (Ag⁺, Cu²⁺, Fe²⁺, Fe³⁺, Mg²⁺, Ni²⁺, Ba²⁺, Cr³⁺, Ca²⁺, Co²⁺, Na⁺, Pb²⁺, Zn²⁺, Li⁺, Mn²⁺, Al³⁺, K⁺ and Cd²⁺) in the pH range 6.9–8.0. As a Hg²⁺ probe, the iridium(III) complex exhibited low detection limits of 8.074 × 10⁻⁸ M (16 ppb) by luminescence detection and 3.985 × 10⁻⁷ M (80 ppb) by absorption detection.