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Abstract. The importance of detailed thermodynamic studies in assessing the selective behaviour of macrocyclic receptors for one species relative to another in a given solvent and the medium effect on complexation processes involving ionic species are emphasised. Factors to be considered in the determination of thermodynamic parameters of complexation in non-aqueous solvents are highlighted. Particular reference is made to the need for considering the bulk of information available in the literature on the solution properties of electrolytes in non-aqueous medium in the selection of the solvent for ion complexation processes involving macrocycles.A detailed thermodynamic study on the interaction of p-tert-butyl calix[n]arene (n = 4−6) tertiary amide derivatives with uni-and bivalent cations in protic (methanol) and dipolar aprotic (acetonitrile) media is reported. It is demonstrated that as the number of phenyl units in the macrocycle increases, the vital feature of the cyclic tetramer receptor for selective recognition of cations decreases significantly for the cyclic pentamer and almost disappears for the hexamer. Concluding remarks are included. (doi: 10.5562/cca2170)

A ditopic calix[4]pyrrole amide based ion selective electrode and its applications are first reported. Sodium tetraphenylboron currently used as additive in Hg ISE is by itself a sensor for mercury(ii).

Materials used in current technological approaches for the removal of mercury lack selectivity. Given that this is one of the main features of supramolecular chemistry, receptors based on calix[4]arene and calix[4]resorcarene containing functional groups able to interact selectively with polluting ions while discriminating against biologically essential ones were designed. Thus two receptors, a partially functionalized calix[4]arene derivative, namely, 5,11,17,23-tetra-tert-butyl [25-27-bis(diethyl thiophosphate amino)dihydroxy] calix[4]arene (1) and a fully functionalized calix[4]resorcarene, 4,6,10,12,16,18,22,24-diethyl thiophosphate calix[4]resorcarene (2) are introduced. Mercury(II) was the identified target due to the environmental and health problems associated with its presence in water Thus following the synthesis and characterization of 1 and 2 in solution ((1)HNMR) and in the solid state (X-ray crystallography) the sequence of experimental events leading to cation complexation studies in acetonitrile and methanol ((1)H NMR, conductance, potentiometric, and calorimetric measurements) with the aim of assessing their behavior as mercury selective receptors are described. The cation selectivity pattern observed in acetonitrile follows the sequence Hg(II) > Cu(II) > Ag(I). In methanol 1 is also selective for Hg(II) relative to Ag(I) but no interaction takes place between this receptor and Cu(II) in this solvent. Based on previous results and experimental facts shown in this paper, it is concluded that the complexation observed with Cu(II) in acetonitrile occurs through the acetonitrile-receptor adduct rather than through the free ligand. Receptor 2 has an enhanced capacity for uptaking Hg(II) but forms metalate complexes with Cu(II). These studies in solution guided the inmobilization of receptor 1 into a silica support to produce a new and recyclable material for the removal of Hg(II) from water. An assessment on its capacity to extract this cation from water relative to Cu(II) and Ag (I) shows that the cation selectivity pattern of the inmobilized receptor is the same as that observed for the free receptor in methanol. These findings demonstrate that fundamental studies play a critical role in the selection of the receptor to be attached to silicates as well as in the reaction medium used for the synthesis of the new decontaminating agent.