ALKALI-METAL ION COMPLEXES OF THE CALIXARENES .1. CESIUM BONDING IN CALIX[4]ARENE SYSTEMS

A crystal structure determination on the monocaesium derivative of bis (homooxa)-p-tert-butylcalix[4]-arene (L2), [Cs(L2 - H)(OH2)3].xH2O (x almost-equal-to 3) [orthorhombic, Pmnb, a = 26.666(5), b = 15.928(4), c = 11.499(9) angstrom, z = 4, R = 0.071 for 1500 'observed' reflectio ns] showed that the caesium may be considered to be involved in polyha pto interactions with carbon atoms in two of the four phenyl rings as well as co-ordination to two phenolic oxygens, the ether oxygen and th ree water molecules. The nature of the polyhapto aromatic interactions seems to be similar to that of those previously observed as the exclu sive mode of calixarene binding in the caesium complex of the monoanio n of p-tert-butylcalix[4]arene. Both complexes can be described as cat ion inclusion compounds, and the retention of this solid-state structu re in some solvents is associated with very low-field Cs-133 nuclear m agnetic resonances. On the basis of Cs-133 NMR spectra, it can be conc luded that a series of calix[4]arenes bridged at the upper rim by an a liphatic chain -(CH2)n- also forms inclusion complexes with Cs+ for n = 7-10, in accord with Cs+ transport studies previously reported for a similar series.