Triply interlocked covalent organic cages

Abstract

Interlocked molecules comprise two or more separate components that are joined by 'mechanical' rather than covalent bonds. In other words, these molecular assemblies cannot be dissociated without the cleavage of one or more chemical bonds. Although recent progress has enabled the preparation of such topologies through coordination or templating interactions, three-dimensional interlocked covalent architectures remain difficult to prepare. Here, we present a template-free one-pot synthesis of triply interlocked organic cages. These 20-component dimers consist of two tetrahedral monomeric cages each built from four nodes and six linkers. The monomers exhibit axial chirality, which is recognized by their partner cage during the template-free interlocking assembly process. The dimeric cages also include two well-defined cavities per assembly, which for one of the systems studied led to the formation of a supramolecular host-guest chain. These interlocked organic molecules may prove useful as part of a toolkit for the modular construction of complex porous solids and other supramolecular assemblies.

Topological landscapes of porous organic cages

“…Alternative products could include a range of different size oligomeric products, a polymeric material, alternative molecules with different topologies, or catenated molecules. Whilst reports of catenanes for porous organic cages are so far rare, examples from Hasell et al 37 and Zhang et al 38 suggest that in some cases catenanes can be the thermodynamic product, rather than their monomeric equivalent, as a result of 'self-templating' driven by the introduction of intermolecular interactions such as π-π stacking and alkyl-π interactions in the catenated form. In general, it is likely that, dependent on after how much time the product is isolated and characterised, different products might be observed as the mixture evolves.…”

Porous organic molecular solids by dynamic covalent scrambling

“…We exploit here the dynamic nature 35,36 of the imine bonds in cages 1 and 3 to form new cage molecules with mixed vertex functionalities. This can be achieved in three different ways.…”

A synthetic molecular pentafoil knot

“…Although other syntheses of trefoil knots have been reported [15][16][17][18][19][20][21][22] (as have composites of trefoil knots 23 and other molecular topologies such as catenanes [24][25][26][27][28] and Borromean links 29 ), higher-order molecular knots remain elusive. Here, we report on the synthesis of a molecular pentafoil knot that combines the use of metal helicates to create crossover points 30 , anion template assembly to form a cyclic array of the correct size [31][32][33] , and the joining of the metal complexes by reversible imine bond formation 34-37 aided by the gauche effect 38 to make the continuous 160-atom-long covalent backbone of the most complex non-DNA molecular knot prepared to date.…”