lonophores of the bis(crown ether) type, with polyamine linkers, examples of which are known to bind simultaneously to a cation and its counter anion, have been prepared. One-pot reductive amination, used to couple a benzo-crown aldehyde with aliphatic (both linear and cyclic) and aromatic polyamines, proved to be the most efficient route. A strong inhibition of one synthetic route (amine benzylation) was observed.The competitive interaction between chloride and other anions for binding with the protonated ionophores was examined using 35CI N M R spectroscopy. Sandwich complexing of potassium contrasting with single-face complexation of sodium was demonstrated by 13C N MR spectroscopy.Biological systems frequently organise a molecule with two distinct subunits by a strong ionic or co-ordinative type interaction with a metal ion, which holds the units in position for some other biological strategy. For example the two halves of the iron protein of the nitrogenase complex are organised by an Fe,S, cluster linked to cysteines coming from each half, forming a receptor site into which fits the ATP/ADP unit involved in energy transfer for the hydrogenation of dinitrogen. Such examples have prompted chemical mimicry. In this work a promising bis(crown ether) structure was designed to co-ordinate anions within a cavity produced by organisation of the two ends of the molecule with a strong interaction. In the examples tried ' this 'organisation' is a sandwiching of an alkalimetal cation between two crown ethers. Molecules containing two crown ether moieties, separated by a linking group, are known to sandwich potassium but crystallographic evidence of the structure has been sparse. A recent crystal structure determination of a rubidium complex of a Schiffbase-linked bis(crown ether) shows a double sandwich structure, not previously demonstrated.' This has a potential binding site between the two aromatic fragments which link the two crowns of each individual bis(crown ether), which may be represented as shown in Scheme 1, which we have used previously to describe our designThe 1 : 1 sandwich structure (see Scheme 1) has also been demonstrated crystallographically.6 This paper gives details of synthetic routes to, and the separation and characterisation of, multireceptors which should exhibit multiple binding as outlined by us previously in a preliminary report.' 1980,47,81.

This paper reports the synthesis and characterisation of the first multi-receptors [bis(crowns) with polyamine linkers] to exhibit multiple binding to anions and their counterions simultaneously.It has been known for some time that molecules containing residue, then in hydroxylic solvents, even at neutral pH, two crown ether moieties, separated by a linking group, will where it would be partly protonated, such a molecule should sandwich potassium cations,l and it has been postulated that be capable of complexing the counterion of its potassium the linker between the two crown rings will form a pocket.* It 'filling'. This paper reports a synthetic route, and the occurred to us that if the linker were formed from a polyamino separation and characterisation of the first such multi-recep-

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7-Zirconium phosphate-phosphite, ~/-Zr.PO 4, H2POy 2H20, (7-ZrPP), was prepared and characterized. Direct treatment of 7-zirconium phosphatephosphite with an ethanol solution of 0.IM 1,10-phenanthrolin and 2,2'-bipyridyl gave the well defined composites, 7-Zr.PO4-H2PO3(phen)0.~5.H20 and 7-Zr.PO4.HzPO3(bipy)0.18.0.6H20 respectively. K d values of a mixture of lanthanide ions: La 3+, Sm 3+, Eu 3+ and Yb 3+ for the intercalated products and for 7-ZrPP in HNO 3 solution at room temperature and at pH 2 and 4 were determined by a radiotracer technique. 14~ 152mEu, 153Sm and 175yb radioisotopes were used for the equilibration experiment using 500 ~tl (4.0.10 -s mmole) each of the solutions of the tracers as a mixture in 7.5 M HNO 3 solution at the desired pH with 0.l g of 7-ZrPP and of the intercalated products. The selectivity order was found to be dependent on the nature of the ligand and on the pH. The 2,2'-bipyridyl product posseses, at pH 2 in general, a high K a value, specially for Sm 3+ (9815.9) compared to that of the 1,10-phenanthrolin product (3375.5) and to 7-ZrPP (419.8). This could be attributed to partial deintercalation of the 2,2'-bipyridyl at pH 2 and increasing of ionogenic groups.

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Glassy tin arsenate, Sn(HAsO4)2-2.7H20 (SnAs) was prepared and characterized. The uptake of lanthanide ions La 3+, Sm 3+, Eu 3+, and Yb 3+ was followed on the glassy tin arsenate in HNO 3 solution at pH 1,2 and 4. The radiotracers are 14~ I53Sm, I52mEu, and ~75yb. 500p_l (4.0.10 -5 mmole) of each solution of the tracer as a mixture plus 7.5 ml HNO 3 solution at the desired pH were equilibrated with 0.1 g of SnAs.The selectivity order (K a values) was found to be dependent on the pH. At pH 2 the K a values were high for all the studied metal ions