Metal ion complexation by tetraphosphonate cavitands: The influence of the ionic radius

Two new complexes formed by tetraphosphonate cavitands with lead and copper salts, resp., have been prepd. and characterized in the solid state through X-ray diffraction anal. In both cases, dimeric capsules are obtained, whose architecture depends on the cation dimensions: the coordination of the phosphonate groups to the metal center is direct in the case of lead, but it is mediated by an aquo complex through a second-coordination sphere in the copper compd. [on SciFinder(R)