Novel Ca2+-selective merocyanine-type chromoionophore derived from calix[4]arene-diamide

The synthesis and calcium-selective chromogenic ion binding properties of benzothiazolium derivative of calix[4]arene are described. The merocyanine-type ionophore derived from calix[4]arene-diamide showed selective chromogenic properties toward Ca2+ ions in aqueous methanol. The compound showed significant Ca2+ ion dependent changes in UV–vis spectral properties in the presence of other physiologically important metal ions (Na+, K+, and Mg2+). The pH sensitive chromogenic behavior also suggests that the compound can be used as a sensitive pH indicator around pH 6.5.