Highly silver ion selective fluorescence ionophore: Fluorescent properties of polythiazaalkane derivatives bearing 8-(7-hydroxy-4-methyl)coumarinyl moiety in aqueous solution and in liquid–liquid extraction systems

Two novel fluoroionophores, N-(7-hydroxy-4-methylcoumarin-8-ylmethyl)-3,9-dithia-6-azaundecane (1) and N-(7-hydroxy-4-methylcoumarin-8-ylmethyl)-3,9-dithia-6-azaundecane (2), were synthesized as fluorescence extractants for selective silver determination. The absorption and fluorescence spectra were measured in aqueous 1,4-dioxane solution (28 v/v%) in the absence and presence of silver ion, and their acid dissociation constants were determined from the pH-dependent spectral changes. In the liquid–liquid extraction of some metal ions from neutral aqueous solution into dichloromethane phase, compounds 1 and 2 exhibited excellent silver ion selectivity, and dramatic fluorescence spectral changes were observed in the dichloromethane solutions containing these compounds. The determination limit of 2 for silver ion was 2.0 × 10−8 mol dm−3 in the liquid–liquid extraction.