p-Sulfonatocalix[4]arene binding of monovalent, divalent and trivalent metal ions

Structural studies on p-sulfonatocalix[4]arene coordination compounds involving diverse metal ions with respect to their size and charge, caesium(I), copper(II) and neodymium(III) are reported. The metal coordination-driven self-assembly forms metallosupramolecules, either as a two-dimensional (2 D) or a three-dimensional (3D) network while retaining the commonly established bilayer array for p-sulfonatocalix[4]arene. The complex (Cs₅-p-sulfonatocalix[4]arene-H⁺)·6H₂O has five crystallographically independent caesium(I) ions with high coordination numbers. In the divalent complex {[Cu₃(H₂O)₁₂-2(p-sulfonatocalix[4]arene)]^2-}·2([Cu(H₂O)₅])²⁺·2NO₃^-·7H₂O, two different copper(II) coordination environments are present, one with octahedral stereochemistry while bridging two opposing calixarenes with the other having a square pyramidal geometry involving one sulfonate group. Eight-coordinate neodymium(III) metal ions prevail in Nd_0.25(H₂O)_1.25(p-sulfonatocalix[4]arene + H⁺)_0.25, involving four sulfonate groups from four different calixarenes.