Guest inclusion properties of a novel cage molecule composed of two calix[4]arenes

The biscalix[4]arene was synthesized by connecting the upper rims with two spacers. The inclusion ability and the selectivity for various quaternary ammonium ions were enhanced due to the cooperative action of the cation–π interaction in the two bowl-shaped calix[4]arenes. The very slow dynamic process during complexation and decomplexation and the separation of the cationic guest and the counter anion were caused by encapsulation of the biscalix[4]arene.