We report an enantioselective catalyst based on a ''mechanically chiral'' rotaxane. Catalysis with chiral molecules is extremely important in modern chemistry because it is one of the most efficient ways to make chiral molecules for applications in many areas. Our results demonstrate, for the first time, that mechanically chiral molecules are a promising and underexplored platform for generating such catalysts. We achieve enantioselectivities for the Au I -catalyzed Ohe-Uemura cyclopropanation of benzoate esters comparable to previously reported covalent catalysts.

Mechanically interlocked molecules are perhaps best known as components of molecular machines, a view further reinforced by the Nobel Prize in 2016 to Stoddart and Sauvage. Despite amazing progress since these pioneers of the field reported the first examples of molecular shuttles, genuine applications of interlocked molecular machines remain elusive, and many barriers remain to be overcome before such molecular devices make the transition from impressive prototypes on the laboratory bench to useful products. Here, we discuss simplicity as a design principle that could be applied in the development of the next generation of molecular machines with a view to moving toward real-world applications of these intriguing systems in the longer term.

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Rotaxanes can display molecular chirality solely due to the mechanical bond between the axle and encircling macrocycle without the presence of covalent stereogenic units. However, the synthesis of such molecules remains challenging. We have discovered a combination of reaction partners that function as a chiral interlocking auxiliary to both orientate a macrocycle and, effectively, load it onto a new axle. Here we use these substrates to demonstrate the potential of a chiral interlocking auxiliary strategy for the synthesis of mechanically planar chiral rotaxanes by producing a range of examples in high enantiopurity (93–99% e.e.), including so-called ‘impossible’ rotaxanes whose axles lack any functional groups that would allow their direct synthesis by other means. Intriguingly, by varying the order of bond-forming steps, we can effectively choose which end of an axle the macrocycle is loaded onto, enabling the synthesis of both hands of a single target using the same reactions and building blocks.

Anion-coordination-driven assembly (ACDA) is showing increasing power in the construction of anionic supramolecular architectures.H erein, by expanding the anion centers from oxoanion (phosphate or sulfate) to organic triscarboxylates,a nA rchimedean solid (truncated tetrahedron) and ah ighly entangled, double-walled tetrahedron featuring ar avel topology have been assembled with tris-bis(urea) ligands.T he results demonstrate the promising ability of triscarboxylates as new anion coordination centers in constructing novel topologies with increasing complexity and diversity compared to phosphate or sulfate ions on account of the modifiable sizea nd easy functionalization character of these organic anions.

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Biological encapsulants, such as viral capsids and ferritin protein cages, use many identical subunits to tile the surface of a polyhedron. Inspired by these natural systems, synthetic chemists have prepared an extensive series of artificial nanocages, with well-defined shapes and cavities. Rational control over the self-assembly of discrete, nanometre-scale, hollow coordination cages composed of simple components still poses considerable challenges as a result of the entropic costs associated with binding many subunits together, difficulties in the error-correction processes associated with assembly, and increasing surface energy as their size grows. Here we demonstrate the construction of a family of nanocages of increasing size derived from a single simple pentatopic pyrrole-based subcomponent. Reasoned shifts in the preferred coordination number of the metal ions employed, along with the denticity and steric hindrance of the ligands, enabled the generation of progressively larger cages, incorporating more subunits. These structural changes of the cages through these ‘mutations’ are reminiscent of differences in the folding of proteins caused by minor variations in their amino acid sequences; understanding how they impact capsule structure and thus cavity size may help to elucidate construction principles for still larger, more complex and functional capsules, capable of binding and carrying large biomolecules as cargoes.