Research on mechanically interlocked molecules has advanced substantially over the last five decades. A large proportion of the published work focusses on the synthesis of these challenging targets, and the subsequent control of the relative position of the covalent sub-components, to generate novel molecular devices and machines. In this Feature Article we instead review some of the less discussed consequences of mechanical bonding for the chemical behaviour of catenanes and rotaxanes, and their application in synthesis, including striking recent examples of molecular machines which carry out complex synthetic tasks.

We present a simple approach to bipyridine macrocycles in remarkable yields (typically >65%) and demonstrate their application in efficient rotaxane synthesis.

CONSPECTUS: Fullerene (C 60 ), a π-conjugated cage molecule consisting of 60 sp 2 -hybridized carbon atoms that are arranged into perfect icosahedral symmetry, is one of the most extensively studied nanocarbon materials by virtue of its characteristic spherical structure, fascinating optoelectronic properties, and widespread applications in material science. To implement practical applications, C 60 is generally used as a building motif to assemble into various ordered superstructures. Unlike the controllable face-to-face π−π interactions of planar π-conjugated molecules, the π−π interactions between the three-dimensional spherical C 60 units are random and directionless, which generally lead to complicated aggregated structures and unpredictable properties. The primary target of our research is to produce a robust design strategy for functional C 60 materials, by which the single C 60 molecules can be engineered into desirable self-organized architectures with optimized functions. To this end, we focused on alkylated fullerene (alk-C 60 ) derivatives, a simple molecular system whose two components, alkyl chains and C 60 , exhibit both hydrophobicity yet different affinities to organic solvents. As a result, the alk-C 60 derivatives present an unusual "hydrophobic amphiphile" system. Through systematic tuning of the substitution pattern of a series of alkyl side chains (number, length, branching, and substitution position) and external experimental conditions, the factors influencing alk-C 60 selfassembly behaviors were determined. In addition, the feasibility of forming hybrid coassemblies with alk-C 60 and other nanocarbon materials was demonstrated. By taking full advantage of the hydrophobic nature and active optoelectronic properties of these self-or hybrid-assemblies, various superhydrophobic materials and/or optoelectronic devices were developed. However, supported only by weak noncovalent interactions, these ordered superstructures are intrinsically fragile under various external stimuli. To improve the structural stability and achieve consistent optoelectronic performance of these novel materials, we strengthened the ordered structures via metallization and plasticization. Both approaches gave rise to robust and endurable materials with functions inherited from the pristine assemblies but at the cost of their former softness and facile processability. Thereafter, we focused on amorphous materials in view of their consistent and predictable optoelectronic properties that are independent of their geometry and physical environment. Unexpectedly, the amorphous materials obtained were liquids at room temperature, whose excellent deformability might enable applications in flexible/wearable optoelectronic devices. However, the lack of sufficient molecular order impaired their optoelectronic performance. To address this, we devised a straightforward strategy toward the directed ordered self-assembly of the alk-C 60 liquids by adding molecular cofactors (nalkanes or C 60 ) into the liquids. Using this strategy, t...

We demonstrate that, depending on reaction conditions, [2]rotaxanes are produced in essentially quantitative yield in the AT-CuAAC reaction regardless of macrocycle size, and hard to access doubly threaded [3]rotaxanes can be synthesised in up to 50% isolated yield in a four component coupling step.

In this proof‐of‐concept study, an active‐template coupling is used to demonstrate a novel kinetic self‐sorting process. This process iteratively increases the yield of the target heterocircuit [3]rotaxane product at the expense of other threaded species.