Adsorptive stripping analysis and monolayer properties of crown ethers with an azo unit in the macrocycle

Abstract

Adsorptive stripping voltammetry was used for trace measurements of 13-membered crown ethers with a cis-azo unit (1,2-dehydro-1,2-diaza-3,4 : 12,13-dibenzo-5,8,11-trioxacyclotridecane). The voltammetric signal is sensitive both to the structure of the azo compound and to the supporting electroltye salt. The analytical procedure allows one to determine the compounds down to 1 × 10^–9 mol l^–1 and is used to estimate the solubilities of the azocrowns in aqueous solutions. The least soluble compounds were found to form stable monolayer films at the water/air interface. The surface pressure versus molecular area isotherms were used to calculate the mean area per molecule in the monolayer of amphiphilic azocrown derivatives on the water surface and to compare this value with the area occupied by azocrown molecules in the monolayers adsorbed on mercury.