Organoiridium(III) complex-based probe for rapid and highly selective dual channel detection of cyanide ion

Abstract

A new d6-metal complex-based probe, [Ir(ppy)₂(L)]⁺ (L = 1,10-phenanthroline-4,7-dicarboxaldehyde) (Ir-1), was synthesized and fully characterized using various spectroscopic techniques. Ir-1 was employed for cyanide (CN⁻) detection via cyanohydrin formation. Its CN⁻ binding properties were systematically investigated in pure acetonitrile using UV–vis absorption and photoluminescence(PL) spectroscopy. The addition of 2.0 equivalents of CN⁻ to a 25 µM Ir-1 in acetonitrile resulted in a drastic 103-fold enhancement in photoluminescence intensity, with the appearance of bright green luminescence. The detection limit was determined to be 10.56 × 10⁻⁶ M. Cyanohydrin formation was further confirmed through ¹H NMR spectroscopy with 2 equivalents of CN⁻. Additionally, CN⁻ detection was demonstrated using probe-loaded paper strips with a 100 µM analyte solution. Finally, density functional theory (DFT) calculations were performed to explore the electronic structure and transitions in Ir-1 and its cyanide adduct.