Bis(crown ether) Dyes Incorporating Azophenol Structure

Abstract

Abstract Three types of bis(crown ether) dyes bearing one or two azophenol units were synthesized, which may be expected to show different cation-complexing properties from the corresponding monocyclic crown ether dyes. The extraction of alkali and alkaline-earth metal salts with the crown ether dyes suggested that some cooperative action of the two adjacent crown ether moieties of the bis(crown ether)s occurs on complexing metal cations, although the bis(crown ether) effect is not very remarkable.