Design and construction of multicomponent spheroidal assemblies on the nano-scale via the self-assembly approach

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Supramolecular chemists can be thought of as the architects of the nano-scale world. We are primary concerned with the design and construction of various nanostructures based upon geometric shapes of smaller building blocks and controlling intermolecular non-covalent bonding. Indeed, chemists have borrowed the ideas and principles from the biological and mathematical world to design a wonderful array of interesting molecular topologies. All of the important chemical and biological processes needed for life occur within molecular containers such as viruses, bacteria and biological cells. Although chemists are far from the development of artificial container structures that can reproduce the remarkable properties of biological cells, greater success has been achieved by modeling capsule structures based upon viruses. Supramolecular chemistry, the all-in-one self-assembly approach which combines the advantages of reversibility and error checking based upon self-complementary hydrogen bonding has resulted in the formation of nanometer-sized spheroidal structures. he following dissertation comprises three closely related sets of studies, the design and construction of large spherical multicomponent assemblies via the selfassembly approach. Chapter 2 will describe the formation of very large molecular capsules based upon the self-assembly of six macrocycles called the C-alkylpyrogallol[4]arenes. These molecular capsules are held together by numerous hydrogen bonds and enclose approximately 1200 [angstrom][superscript 3] of inner space. Chapter 3 will discuss a new design approach to large multicomponent metalligand coordination capsules. All the metal-directed self-assembly methods reported within the literature use metal-ions as the directing influence in ligand assembly (i.e. without the metal-ions, the ligands would not assemble into spheroidal structures). However the C-alkylpyrogallol[4]arene molecules can assemble into hexameric nanospheroids with or without the presence of metal-ions. Topologically any closed two-dimensional surface can principally be described as a sphere or as a torus-shaped structure. The relationship between the two topologies continues to grab attention for understanding numerous topological and chemical problems. Indeed, given the numerous torus-shaped structures formed by molecular covalent chemistry there are surprisingly few non-covalent equivalents and their synthesis represents an enduring challenge for synthetic chemists. Thus, chapter 4 will describe the self-assembly of six molecules called calix[4]arenes into a large torusshaped structure via hydrogen bonding. The toroidal structure is structurally related to the calix[4]arene nanospheroids