Molecular Borromean rings and Solomon knots

This dissertation focuses on the synthesis, characterization and analysis of topologically linked molecules, known as Borromean rings (BRs) and Solomon knots (SKs). With the advent of new synthetic methodologies that are advancing under the umbrella of template-directed synthesis, chemists are beginning to appreciate the subtleties of topologically interesting structures, and consequently have pursued their synthesis. The construction of molecules having the Borromean ring (BR) topology represents a formidable synthetic challenge, since it consist of three mutually interlocked, yet not catenated rings. The efficient molecular construction of the BR topology has been achieved successfully from 18 individual components under strict dynamic covalent, coordinative and supramolecular control. The dynamic construction of the BR topology can be predicated on the premise of controlling the placement of 12 organic ligands around six transition metals. Stabilized by combinations of 12 pi--pi stacking interactions and 30 dative bonds, six tridentate and six bidentate ligands are spatially preorganized around six transition metal atoms. Molecular Borromean rings are formed in a single step in yields greater than 95%.;From a design angle, this molecular BR topology provides a unique symmetrical, nanoscale three-dimensional scaffold into which unique features ( e.g., electroactive, photoactive, and chiro-optical) can be imbedded. Taking advantage of the ability to preorganize six metal ions spatially and symmetrically, other redox-active metals were used to construct a range of Borromeates. Conditions were used in which metals were mixed in the reaction, and this mixing led to the formation of another topological entity, known as King Solomon's link, in which two of the same rings as are present in the molecular BRs are doubly catenated. This finding suggests that there is a dynamic combinatorial library from which it is possible, during a crystallization process that is kinetically controlled, to amplify one of the members of the library. This hypothesis was further demonstrated by the formation of a molecular SK under homo-metal conditions in which the only condition varied was the choice of crystallization solvents. The synthesis of molecular BRs has been optimized--even to the point where it has been incorporated for educational purposes into an undergraduate curriculum on a gram-scale. There will likely be other exotic topologies that emerge from the dynamic library of knots and links that compete with each other in the formation of the molecular BRs and SKs.