R. Assmus et al., ALKALI-METAL ION COMPLEXES OF THE CALIXARENES .1. CESIUM BONDING IN CALIX[4]ARENE SYSTEMS, Journal of the Chemical Society. Dalton transactions, (16), 1993, pp. 2427-2433
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.