Topological landscapes of porous organic cages

Abstract

We define a nomenclature for the classification of porous organic cage molecules, enumerating the 20 most probable topologies, 12 of which have been synthetically realised to date. We then discuss the computational challenges encountered when trying to predict the most likely topological outcomes from dynamic covalent chemistry (DCC) reactions of organic building blocks. This allows us to explore the extent to which comparing the internal energies of possible reaction outcomes is successful in predicting the topology for a series of 10 different building block combinations.

Shape‐Persistent [4+4] Imine Cages with a Truncated Tetrahedral Geometry

“…To efficiently synthesize shape‐persistent organic cages in high yields, dynamic covalent chemistry (DCC) turned out to be the synthetic method of choice . Cages of various sizes and geometries should be accessible by choosing the right precursors . And indeed a large number of geometries and topologies have been realized till date including prisms, tetrahedra, cubes, cuboctahedra, octahedra, tetrapods and others…”

Organic Cage Dumbbells

“…Previously, a range of Tri 2 Di 3 species have been reported that are formed using an imine condensation strategy—these cage molecules consist of two tri‐topic and three di‐topic building blocks . Following this, we reported a high‐throughput workflow that used a robust synthetic method for organic cage discovery, that also included a number of Tri 2 Di 3 species . While our modelling suggested that organic cages of this topology tend to have cavities that are too small to host gaseous guests based on their kinetic diameters, meaning their porosity is not typically studied, the reduced versions of these small capsular cages, or cryptands/cyclophanes, have been previously studied as binding receptors .…”

“…Our aim was to use a multi‐component imine condensation to access a socially self‐sorted and controlled assembly incorporating more than one cage, instead of self‐sorted binary cages. We therefore decided to investigate the one‐pot multi‐component reaction of a tri‐topic amine and di‐topic aldehyde (as used in the formation of B1 , a Tri 2 Di 3 cage), along with a tetra‐topic aldehyde that has the same 1,3‐dialdehyde substitution pattern (Scheme ).…”

“…We were also interested as to why there was consistent formation of a mixture of both cage and dumbbell, and so we turned to computational modelling to explore this. We showed previously that it is possible to predict the most likely cage topology formed from two precursors by calculating and comparing the formation energies per imine bond for different molecular assemblies . These calculations are performed on isolated molecules in the gas phase, which does not consider solvent effects, and hence large energetic differences are needed to predict solution‐phase structures with confidence.…”

Kovalente organische Netzwerke und Käfigverbindungen: Design und Anwendungen von polymeren und diskreten organischen Gerüsten

“…Santolini et al klassifizierten kürzlich die 20 wahrscheinlichsten Käfigtopologien fürd i-, tri-und tetratopische Vorstufen, [130] von denen zwçlf bereits präparativ realisiert wurden. Santolini et al klassifizierten kürzlich die 20 wahrscheinlichsten Käfigtopologien fürd i-, tri-und tetratopische Vorstufen, [130] von denen zwçlf bereits präparativ realisiert wurden.…”