SYNTHESIS, STRUCTURE AND ALKALI-METAL ION-BINDING PROPERTIES OF A PODAND POLYETHER DERIVED FROM CALIX[4]ARENE, RA-TERT-BUTYL-25,27-DI(PHENYLMETHOXY)-26,28-DI(2'- METHOXYETHOXY)-CALIX[4]ARENE

The ligand ylmethoxy)-26,28-di(2-methoxyethoxy)calix[4]arene, designed as an analogue of some calixcrown species in order to evaluate possib le origins of their selectivity in alkali metal ion binding, has been synthesised and structurally characterised by X-ray crystallography. T he crystals are monoclinic, P2(1)/n, a = 15.940(6), b = 19.388(5), c = 20.020(5) Angstrom, beta = 109.10(2) deg., Z = 4, conventional R on \ F\ being 0.073 for 3454 independent, 'observed' (I > 3 sigma(I)) refle ctions. H-1-NMR studies in 1:1 CD3CN/CDCl3 solvent have shown that the ligand exerts a strong preference for the lighter alkali metal ions ( Li+ and Na+) contrary to the binding behaviour of known calixcrowns. T his may reflect interactions restricted to the lower rim donor atoms w ithout concomitant interaction with the calixarene pi-electrons, perha ps because the latter interactions are substituted by those with the b enzyl group pi-electrons.