Open dimeric and capped polymeric container molecules: calixarene and resorcinarene complexes of AgI co-ordinated by participation of the upper-rim carbon atoms

Abstract

The reactions of C-methylcalix[4]resorcinarene (L¹), calix[6]arene (L²) and calix[4]arene (L³) with silver(I) salts have resulted in the isolation and structural characterization of three dimeric and one polymeric silver derivatives of calixarene based on cation π interactions. The dinuclear cation in [Ag₂(L¹)(C₆H₆)₂][ClO₄]₂·5C₄H₈O 1 contains two symmetry-related metal centers, each involving a rather distorted tetrahedral co-ordination with, in addition to one benzene molecule, both the aryl OH groups and the aromatic rings of resorcinarene. The two dimeric calix[6]arene structures, {[Ag(L²)X]·2C₆H₆}₂, where X = ClO₄^– 2 or CF₃SO₃^– 3, display similar characteristics with two ligand groups inversely linked by the co-ordination of the silver ion to the phenyl carbons. The solvent molecules or the counter anions are not included in the cavity generated by the dimeric unit, but intercalated into calixarene or resorcinarene bilayers. In the calix[4]arene complex [Ag₂(L³)(ClO₄)₂] 4 each of the four phenyl rings is bound to one metal atom which in turn bridges between the two calixarenes leading to an infinite two-dimensional arrangement. The polyoxo anion bridging between silver ions partially caps the container cavity of the calixarene. The factors controlling the selectivity of complexation and inclusion properties of calixarenes are discussed.