Aquacyanocobalt(III)-cobyrinate as a key compound in NO2-sensitive polymeric liquid membranes.

The reactions within a recently introduced NO2-sensitive polymeric membrane based on aquacyanocobalt(III)-cobyrinate are described. The detailed reaction mechanism was investigated in three ways: using UV/VIS-spectroscopy, determining the reaction products and investigating the influence of other gases. It could be shown that the membrane's high sensitivity and selectivity derives from the remarkable reaction of NO2 with this cobyrinate derivative, which yields nitric and nitrous acid. This reaction can be transduced with a consecutive protonation of the included chromoionophore into an optical signal, which allows the detection of NO2 in the ppb-range.