Zn(II)-induced conformational control of amphiphilic cavitands in langmuir monolayers.

The reversible switching from the C(4v)-symmetric vase to the C(2v)-symmetric kite conformation of an amphiphilic resorcin[4]arene cavitand was induced by Zn(II) ion coordination. Langmuir monolayers were obtained of both conformers with the area per molecule increasing dramatically from 120 A(2) for the vase to 270 A(2) for the kite form. (1)H NMR spectroscopy in chloroform solution supports the formation of a stoichiometric kite-cavitand[radical dot](Zn(II))(2) complex, with the metal ions coordinating to pairs of neighbouring quinoxaline N-atoms.