Ammonium ion binding property of naphtho-crown ethers containing thiazole as sub-cyclic unit

Abstract

A short and efficient synthesis, solvent extraction and potentiometric measurements of new thiazole-containing naphtho-crown ethers are reported. The naphthalene moiety enhances the ammonium ion selectivity over potassium ion. The selectivity of NH4+/K+ follows the trend 3 ≈ 2 > 1, indicating that the differences in conformational changes of 2 and 3 in forming ammonium complexes affect little on the resulting ammonium/ potassium extraction selectivity ratio. The ammonium ion-selective electrodes were prepared with n-octylphenyl ether plasticized poly(vinyl chloride) membranes containing 1-4; the effect of one naphthalene unit introduced on either right (2) or left (3) side of thiazolo-crown ether on their potentiometric properties (e.g., ammonium ion selectivity over other cations, response slopes, and detection limits) were not apparent. However, the ammonium ion selectivity of 1, 2 and 3 over other alkali metal and alkaline earth metal cations is 10-100 times higher than that of nonactin.