Acyclic and cyclic polythiamonoaza- and polythiadiaza-alkane hydrazone derivatives as chromogenic extractants for silver ion

Acyclic and cyclic dithiaza-, tetrathiaza- and tetrathiadiazaalkane derivatives bearing 6-trifluoromethyl-2,4-dinitrophenylhydrazono moieties as chromogenic groups on the nitrogen atoms of the alkanes were synthesized and used as extractants for some class ab and b metal ions in liquid–liquid extraction. The extraction behavior was estimated by using the spectral change in the organic phase containing the chromoionophore. All of these compounds exhibited high Ag+ selectivity relative to other class ab and b metal ions, which are soft Lewis acids, even against Hg2+. In the extraction of silver nitrate from aqueous acidic and basic phases, interestingly, the absorption maxima of the organic phases containing the chromoionophores in the visible absorption region shifted to shorter and longer wavelengths, respectively. Among the chromoionophores used here, the acyclic tetrathiazaalkane hydrazone 4b extracted Ag+ most effectively from an aqueous phase into a 1,2-dichloroethane phase under all the extraction conditions studied. A linear calibration graph up to 5.5 × 10–5 mol dm–3 Ag+ in the aqueous neutral phase was obtained spectrophotometrically by using the acyclic tetrathiazaalkane hydrazone 4b and the determination of Ag+ in a silver solder sample was achieved from the calibration graph.