Two Closely Related Iridium(III) Complexes as Colorimetric and Fluorometric Chemodosimeters for Nitrite in Aqueous Solution Operating along Different Modes of Action

Two closely related dual-channel chemodosimeters for nitrite in buffered aqueous acetonitrile were developed using [(pq)2IrCl]2 (1) and [(ppy)2IrCl]2 (2). In the UV–vis channel, the addition of nitrite caused visibly distinct color changes with both probes as a result of sizable absorption intensity enhancements. In the photoluminescence channel, the probes behaved oppositely upon the addition of nitrite. The emission was increased with 1, while it was quenched with 2. NMR and X-ray studies indicated that structurally very different η1-nitrito-N and η2-nitrito-O,O′ complexes were formed. Linear relationships for the quantification were obtained in both channels, allowing one to analyze for NO2– in a range from 5 × 10–5 to 2 × 10–2 M.