Metal organic rotaxane polyhedra (MORPs)

This thesis presents the design and synthesis of [2]pseudorotaxane and [2]rotaxane ligands and their incorporation into Metal Organic Polygons to form Metal Organic Rotaxane Polygons. Chapter 1 introduces the concepts of supramolecular chemistry and coordination-driven self-assembly, as well as interpenetrated and interlocked molecules and discrete self-assembled architectures with definitions and representative examples from the literature. Chapter 2 presents the incorporation of the bis(pyridinium)ethane/24-crown-8 macrocycle recognition motif into molecular squares and molecular necklaces. It describes the synthesis as well as characterization by means of 1D 1H, 13C, and 31P NMR of a series of molecular polygons incorporating a [2]pseudorotaxane as well as the analogous naked axle ligand. Where possible the single crystal X-ray data is presented, where unavailable structure elucidation was via DOSY NMR. Chapter 3 builds upon chapter 2 with the synthesis of an interlocked [2]rotaxane and matching axle intended for incorporation into molecular polygons. Both resulting supramolecular assemblies we successfully crystallized and characterized using single crystal X-ray structure elucidation, and the results confirmed with DOSY NMR. The highlight of this chapter is the single crystal structure of a novel triangular molecular necklace. In chapter 4 a more rigid and compact [2]rotaxane is synthesized to prevent the formation of triangular molecular necklaces during self-assembly. The accompanying axle was also synthesized for comparison. Two supramolecular assemblies are presented. The [2] rotaxane lived up to its design, forming an interpenetrated, catenated square molecular necklace instead of the triangular version as was desired. Chapter 5 presents the synthesis of a novel unsymmetrical [2]rotaxane and its free axle analogue, designed to result in the synthesis of M2L4 molecular cages when combined with naked Pd(II) anions. The design, synthesis, and characterization of the two ligands, as well as efforts toward incorporation into supramolecular assemblies is presented.