Chemical Chromogenic Sensors Based on Calixarenes: Syntheses and Recognition Properties for Alkylamines

Nitration of 1,3-distal dialkylated calix4]arenes wasinvestigated in order to prepare chromogenic sensor compounds. There were three kinds of separableproducts, which came from the nitration and oxidation of the phenol moieties. The coneconformation of calix4]arenes containing a quinone structure was first determined. And the effectof the structure of reactants for the nitration and oxidation is also discussed. Dinitratedcalix4]arenes possess recognition ability for the alkylamines, which can be as the chromogenicsensors for determining the alkylamines. The recognition behavior was due to the protontransfer between alkylamine and calix4]arenes, and the resulting ammonium phenoxide wasstabilized by the phenoxide oxygen atom and the carbonyl at the lower rim with hydrogen bonding.