Chemistry and topology have been curiously linked ever since Lord KelvinÕs initial hypothesis that the elements were simply knots in the fabric of ether. KelvinÕs ideas inspired physicist Peter Tait to begin the tabulation of knots and create the field of topology. It wasnÕt until the first successful synthesis of interlocked rings by Wasserman [1] that chemists were stimulated to draw from the vast array of complex molecular graphs in topology for synthetic targets.
The first examples of molecules with non-trivial topology, catenanes, contain two (or more) interlocked (con-catenated) macrocycles. Equivalent to the Hopf link, these rings are achiral unless both rings are orientated. Even though modern synthetic strategies have enabled the almost routine synthesis of catenanes for a variety of purposes, there are but a few examples of oriented catenanes. By utilizing the well-known coordination chemistry of polypyridines, a set of highly fluorescent oriented ligands have been synthesized leading to the formation and study of topologically chiral catenanes.
Brunnian links are another fascinating set of interlocked rings that while inseparable no one ring is linked through another and the link disassembles when any one ring is removed. The three component link, known as the Borromean Rings is the most well known, and has been an illusive synthetic target since the advent of Chemical topology [2]. Although achievable by a simple thermodynamic self-assembly process, the Borromean link could be realized through a kinetically driven directed synthesis [3]. The step-wise process potentially allows structural variation and the fine-tuning of emergent properties of these intricate molecules.