ChemInform Abstract: Crown Compounds as Alkali and Alkaline Earth Metal Ion Selective Chromogenic Reagents

Abstract

This article deals with the recent development of crown ethers which have added chromophoric functional groups within the molecule (crown ether dyes). These compounds are designed to bring about specific color changes on the interaction with such metal cations as alkali and alkaline earth metals, thus being able to serve as probes or photometric reagents selective for these metal ions. The chromophoric groups can bear a dissociable proton (or protons) or can be nonionic. In the former, the ion exchange between the proton and appropriate metal cations causes the color change, while in the latter, the coordination of the metal ion to the chromophoric donor or acceptor of the dye molecule induces a change of the charge transfer band of the dye. The proton-dissociable crown ether dyes are especially suited for extraction photometric determination of alkali and alkaline earth metal ions. Similarly, the neutral crown ether dyes are potentially useful for such determinations in lipophilic homogeneous media.