Giving an Odor to Carbon Monoxide: Malodorogenic Sensing of Carbon Monoxide via [IrCl(cod)(NHC)] Complexes.

The indirect detection of CO by using impregnated paper strips is reported. The ligand‐substitution reaction of cod by CO in an organometallic complex leads to the liberation of 1,5‐cyclooctadiene (cod), which can be smelled by the human olfactory system with very high sensitivity. Azolium salts tagged with methoxy polyethylene glycols (MeOPEG; 136, 750, and 2000 g/mol) were converted to the respective [IrCl(cod)(MeOPEG‐NHC)] complexes (NHC = N‐heterocyclic carbene). On reaction with CO, [IrCl(CO)2(MeOPEG‐NHC)] and 1,5‐cyclooctadiene are rapidly formed in virtually quantitative yield. Paper strips were coated with a thin film (1–10 µm) of an [IrCl(cod)(MeOPEG‐NHC)] complex. Exposure of the paper to low concentrations of CO (100 ppm) leads to rapid evolution of the strongly smelling olefin. [ABSTRACT FROM AUTHOR]