Multisignaling detection of cyanide anions based on an iridium(III) complex: remarkable enhancement of sensitivity by coordination effect

A new molecule, (Z)-4-(4-(dimethylamino)benzylidene)-3-methyl-1-(pyridin-2-yl)-1H-pyrazol-5(4H)-one (dmpp), and its novel heteroleptic iridium(III) complex, [(ppy)₂Ir(dmpp)]PF₆, were synthesized and characterized. Both dmpp and [(ppy)₂Ir(dmpp)]PF₆ could be used as highly selective and sensitive chemodosimeters for the cyanide anion by the naked eye, owing to the addition of the CN⁻ to the vinyl group of dmpp. The addition of CN⁻ to a solution of dmpp induced a change in the solution color from yellow to colorless, and to [(ppy)₂Ir(dmpp)]PF₆ induced a change in the solution color from pink to colorless. Moreover, [(ppy)₂Ir(dmpp)]PF₆ could also act as a phosphorescent and electrochemical probe of CN⁻. The green phosphorescence band at 520 nm and a new irreversible oxidation wave at 0.423 V showed up upon the addition of CN⁻, indicating that [(ppy)₂Ir(dmpp)]PF₆ was an excellent multisignaling chemodosimeter of CN⁻. Importantly, the Ir complex-based cyanide chemodosimeter [(ppy)₂Ir(dmpp)]PF₆ has much easier and faster detection of CN⁻ than pure organic molecule dmpp.