Facilitated transport of salts by neutral anion carriers

Partitioning of ions from water to the membrane solvent (NPOE) can be quantified by Gibbs free energies of transfer, ΔG_tr,_NPOE(ion). These were derived from transport studies of lipophilic salts through supported liquid membranes (SLMs) in the absence of the carrier. Partition coefficients K_p for various salts can now be calculated. The neutral anion receptors uranyl sal(oph)enes 1-5 transport Cl^- and H₂PO<![IGNORE[$_{4}ˆ{-}$]]> as tetrapropylammonium salts. The transport is diffusion-limited and can be described by two transport parameters D_m and K_ex. From the extraction constants K_ex and the partition coefficients K_p of the transported salts, the association constants K_a of the anion receptors for Cl^- and H₂PO<![IGNORE[$_{4}ˆ{-}$]]> in NPOE were determined. Competitive transport with carriers 3 and 4 of NPr₄H₂PO₄ and NPr₄Cl demonstrated highly selective transport of H₂PO<![IGNORE[$_{4}ˆ{-}$]]> even in the presence of excess of Cl^-.