OCTAANISYL CAVITANDS AND A RELATED CAVIPLEX

The macrocyclic host (46),27,29,31(47),32,34,36(48),37,-39-tetracosaen e [(I), C64H64O8] contains a cavity lined with eight O atoms. This 'ca vitand' complexes a caesium ion more strongly than any other alkali-me tal ion, as expected from molecular models. The structure of a CH2Cl2 solvate of (I) [which we term (Ia)] was determined at 113 K. The confo rmation of the macrocycle appears to be stabilized by the intrusion of a 4-methyl group from a neighboring molecule. This conclusion was rei nforced by the determination, at 115 K, of the structure of the ethano l solvate (Ib) of the same host, and by the fact that a similar mutual orientation of a 4-methyl group of a neighboring molecule and the hos t ring was found. The structure of the caesium complex (Ic) of the sam e host was determined at 115 K; the ion makes the host much more symme trical, with site symmetry m (molecular symmetry nearly mm2). The crys tal structure of 6(46),27,29,31(47),32,34,36(48),37-39-tetracosaene [( II), C56H48O8], which lacks the eight 4-methyl groups of (I), was dete rmined at room temperature; one methoxy group is disordered. No suitab le crystals of a caesium complex of (II) could be grown.