Synthesis and crystal structure of sodium and caesium ion complexes of unsubstituted calix[4]arene.: New polymeric chain arrangements

Calix[4]arene, devoid of p-alkyl substituents, has been used to complex sodium and caesium ions in a basic medium. The crystal structures of one sodium and two caesium complexes are reported and compared to previous structures with related p-tert-butylcalixarenes. The sodium complex is dimeric. two cations being sandwiched between two mono-anionic calixarenes through O-coordination, and bound also to three acetone molecules (one bridging) in the median plane. Both caesium complexes are polymeric, with a stacking of alternate cations and mono-anionic calixarenes, with both polyhapto bonding and O-coordination. This novel arrangement is attributed to the lack of bulky p-substituents in the ligand, which enables the cation included in the cavity of one calixarene to be closely approached by the oxygen donors of a second one on the other side. (C) 2002 Elsevier Science Ltd. All rights reserved.