Alkali cation complexation by 1,3-alternate calix[4]-biscrown-6 in acetonitrile/water mixture solvent

The complexive abilities of 1,3-alternate calix[4]-bis-crown-6 (L) towards alkali metal ions in the acetonitrile/water (90/10) mixture have been evalu ated by UV/Vis spectroscopy. The results reveal that the ligand is capable to complex sodium, potassium, rubidium and cesium ions with a 1:1 metal to ligand ratio. The selectivity presented by L (Cs>K>Rb>Na) in the studied mi xed solvent differs from those observed in pure acetonitrile and methanol. H-1-NMR experiments provide some information that leads to conclude the pro bability of the formation of the 2:1 (metal/ligand) complexes. The latter c omplex was not detected by UV/Vis spectroscopy.