Stoichiometry of uranyl salophene anion complexes

In PVC/NPOE ion-selective membranes of potentiometric sensors, the guest-host stoichiometry of the anion complex of H2PO4- and F- selective uranyl salophene derivatives is 2:1. This stoichiometry is different from the stoichiometry observed in DMSO solution (H-1 NMR) or solid state (X-ray crystal structure). However, the 2:1 stoichiometry like that in the PVC/NPOE membrane matrix is also observed by IK NMR spectroscopy in nonpolar solvents such as chloroform. In contrast with the relatively hard H2PO4- and F- anions, the softer Cl- is bound in a 1:1 stoichiometry by the uranyl salophenes in chloroform.