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The co-transport of alkali thiocyanates, at 2OoC, from an aqueous source solution into an aqueous receiving solution through a bulk liquid dichloromethane solution, is facilitated by p-tert-butylcalix-[nlarene esters of lower rim calixarene acetic acids, named ethyl esters (n = 4, 5, 6, 8), by pdealkylated calix[6]arene ethyl ester and the diethyl and pyrrolidine amides of a p-tert-butylcalix[4]arene. The transport rates show that all derivatives, except the octamer, are efficient and selective neutral ionophores for alkaline cations. The amides are better carriers than the esters and the pyrrolidinyl amide is more efficient for Li+, Na' and K' than the diethyl amide. Among the esters, the most efficient, by far, is the pentamer. The tetra-and penta-esters are selective for Na', the hexaester for Cs' and the tetraamides for K'. The Cs+/Na+ selectivity of the hexaester is increased by dealkylation in the para position. The same is shown t o be displayed in extraction. The data are compared with existing stability constant values in methanol and extraction equilibrium constants for alkali picrates, from water t o dichloromethane. New extraction data are provided for at ka I i t h iocya nates.Paper 4/03558B

Three novel lower rim hexamide derivatives 5(6), 7(6), and 9(6) of p-hydroxycalix[6]arene and four octamides 5(8), 7(8)-9(8) derived from the corresponding p-hydroxycalix[8]arene were synthesized, and their potential as extractants in radioactive waste treatment was evaluated, in comparison with upper rim analogues 12(6) and 12(8) and other existing selective neutral ionophores currently used in radioactive waste treatment. Extraction of alkali and alkaline earth metal picrates from water to dichloromethane, and of the corresponding nitrates from acidic water solution simulating radioactive waste, to 2-nitrophenyl hexyl ether (NPHE), showed that the lower rim amides extract divalent cations much better than monovalent ones. The upper rim hexa-12(6) and octamide 12(8) are very inefficient ligands, hardly extracting any cation. In all cases, p-alkoxy octamides are more efficient and selective extractants than the corresponding hexamides. In the case of simulated waste solutions, the distribution coefficients for strontium removal by octamides (6.5 < D(Sr) < 30) are much higher than the corresponding value (D(Sr)) found for dicyclohexyl-18-crown-6 (DC18C6), and the same applies for the strontium/sodium selectivity, which is 6500 < D(Sr)/D(Na) < 30 000 for octamides and 47 for DC18C6. ESI-MS, UV-vis, and X-ray crystal structure studies give consistent results and indicate the formation of 2:1 (cation/ligand) strontium complexes for all octamides tested. Stability constants were determined in homogeneous methanol solution for alkali metal (log beta(11) < or = 2), calcium (4.3 < or = log beta(11) < or = 6.0; 9.4 < or = log beta(21) < or = 12.0), and strontium (5.6 < or = log beta(11) < or = 12.3) ions using a UV-vis competition method with 1-(2-pyridylazo)-2-naphthol (PAN). They confirm the high efficiency and high divalent/monovalent selectivity found in metal ion extraction experiments for the new octamide ligands. Evidence for a positive cooperative effect between the two metal ion binding sites was obtained in the case of the Ca(2+) complex of octamide 1(8).

Stability in aqueous solution of some complexes of heavy metals with diaza‐polyoxamacrocyclic ligands Stability of metal complexes (Mn+ = Cu2+, Ni2+, Co2+, Zn2+, Pb2+, Ag+ and Cd2+) with five diaza‐polyoxamacrocycles (L = [2.1.1], [2.2.1], [2.2.2], [2.1] and [2.2] ) have been determined at 25°, in 0.1 M Et4N+ClO 4− aqueous solutions, by means of potentiometric titrations. All cations form MLn+ complexes; Cu2+ also forms the MHL(n+1)+ protonated species with both [2.2.1] and [2.1.1] ligands. The stability of these complexes has been discussed in terms of structure and by considering the ionic radii of the cations together with the radii of the macrocyclic cavities. Different behaviour is observed between some of these complexes and the well known alkali and alkaline‐earth cryptates, partly due to the more covalent nature of bonds formed by the investigated cations and the donor sites of the ligands. The effect of the substitution of two oxygen by two sulfur atoms in the pentadentate ligand [2.1] on the stability of the complexes is reported.

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