8,16,24,32-Tetramethoxy[2.2.2.2]metacyclophane-1, 9,17,25-tetrayne: A Novel Ionophore Having a Preorganized but Unexpectedly Flexible Cavity

The title cyclophane has a preorganized cavity with about 1.2 A in diameter surrounded by four oxygen atoms (X-ray analysis); however, solvent extraction experiments using alkali metal picrates revealed the unexpectedly flexible nature of the cavity that forms 1:1 complexes with various alkali metal ions with considerably large association constants.