Controlling molecular self-organization: formation of nanometer-scale spheres and tubules

Amphiphilic polyhedron-shaped p-sulfonatocalix[4]arene building blocks, which have been previously shown to assemble into bilayers in an antiparallel fashion, have been assembled in a parallel alignment into spherical and helical tubular structures by the addition of pyridine N-oxide and lanthanide ions. Crystallographic studies revealed how metal ion coordination and substrate recognition direct the formation of these supramolecular assemblies. The addition of greater amounts of pyridine N-oxide changed the curvature of the assembling surface and resulted in the formation of extended tubules.