Tube-Type Coordination Polymers: Two- and Four-Silver(I)-Mediated Linear Networking of Calix[4]arene Tetracarboxylates

Two calix[4]arene tetracarboxylates, [calix[4]arene tetraacetate (K4CTA) and calix[4]arene tetrabenzoate (K4CTB)] as their potassium salts, have been prepared. Employing these as precursors, two Ag(I) coordination polymers incorporating calix[4]arene units have been successfully prepared and their X-ray crystal structures have been determined. In these, the CTA and CTB derivatives are linearly bound to two and four silver atoms, respectively, to generate unusual tubular nanostructures. A comparative NMR study was undertaken to investigate the nature of the metal ion blocking of the tube as observed in the CTA-derived structure. The thermal properties for both coordination polymers were also examined.