A new
application for bis(cyclometalated) iridium(III) species
containing ancillary acyclic diaminocarbene ligands, viz. for sensing
of mercury(II) ions, is disclosed. A family of bis(cyclometalated)
iridium(III) species supported by both parent isocyanide and acyclic
diaminocarbene ligands was prepared, and their electrochemical and
photophysical properties were evaluated, revealing efficient blue-green
phosphorescence in solution with quantum yields of up to 55%. We uncovered
that the photophysical properties of these complexes are dramatically
altered by the presence of metal ions and that the complex [Ir(ppy)2(CN){C(NH2)(NHC6H4-4-X)}]
with an ADC ligand reacts selectively with Hg2+ ions, enabling
its use for sensing of mercury(II) ions in solution. The limit of
detection was as low as 2.63 × 10–7 M, and
additional mechanistic studies indicated the formation of an unusual
dinuclear iridium(III) cyclometalated intermediate, bridged by a mercury
dicyano fragment as a driving force of mercury sensing.