In this article, studies on coordinative properties of 5,11,17,23-tetra-p-tert-butyl-25,27-bis(N-p-nitrophenylureido-butoxy)-26 ,28-dipropoxycalix[4]arene (Cx2) are presented. Since this anion-receptor was previously used as an additive to solid polymer electrolytes, the correlation of the data presented here and the role of anion-receptors in this type of electrolytes is discussed. The formation constants of salt-receptor complexes and receptor self-complexation (dimer formation) are estimated in the solution in the non-interacting solvent using H-1 and F-19 NMR titration. independently, the affinity of the Cx2 to low molecular weight analogs of PEO and some other organic solvents in this system was tested using the same technique. The estimated values of the formation constants are used in the discussion the role of the anion-receptor in the changes of concentration of ions, ionic agglomerates and complexes of Cx2 in the system comprising salt, solid or liquid matrix and anion-receptor. (C) 2009 Elsevier B.V. All rights reserved.