BIPOLAR ION-EXCHANGE RESINS BASED ON FUNCTIONAL ACIDIC TETRAZOLIUM GROUPS - THEIR SYNTHESIS, STRUCTURE AND PROPERTIES

The synthesis of a novel kind of bipolar ion exchangers with a well-de fined structure based on functional acidic 5-thio-2H-tetrazolium group s is described. A macroporous resin with ortho-carboxylic acid groups (m-T1), a gel-type resin with ortho-sulfonic acid substituted tetrazol ium groups (g-T4) and surface modified fibres with ortho-, meta- para- carboxyl-substituted tetrazolium cations (f-T1, f-T2 and f-T3) were pr epared. Immobilisation of appropriate acidic dithizone derivatives ont o the different chloromethylated polymeric supports and subsequent oxi dation yielded the heterocyclic functionalities. The proposed structur e was confirmed by synthesis of free model compounds and comparative I R-spectroscopic investigations. Theoretical calculations of conformati on ant charge distribution were carried out by molecular modeling. The theoretical capacities of the resins calculated from acid-base titrat ions are distinctly lower than the data obtained from elementary analy sis. The results of sorption experiments with electrolytes and conduct ivity measurements do not confirm the expectation of a simultaneous so rption of cations and anions similar to snake-cage polymers. These fac ts can be explained by the formation of an inner salt structure of the functional groups comparable with free betaines in aqueous solution. As a consequence, weak adsorptive dipole-induced-dipole interactions r esult in a specific uptake of Au(III) species from dilute hydrochloric acid media.