Synthesis of molecular nanocapsules for supramolecular host-guest chemistry and enzyme-like catalysis

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Coordination-driven self-assembly has led to the realization of an increasing number of elegant and sophisticated functional structures, the structural complexity of which would be difficult to achieve using conventional covalent chemistry. The synthesis of three-dimensional coordination capsule-like structures is of particular interest due to their multiple potential applications, particularly their use in selective molecular recognition (host-guest chemistry), reactivity modulation (nanoreactors), molecular sensors or biological applications. The main goal of this doctoral thesis, performed in the QBIS-CAT group from the University of Girona, is the preparation of coordination nanocapsules of different sizes (1 and 2) and their application in the selective recognition of specific molecular substrates. On one hand, the smaller capsule (1) displays high selectivity towards anionic, planar-shaped -guests, whilst on the other hand, the larger nanocapsule (2) is able to encapsulate fullerenes in a rapid manner at room temperature, by simply soaking a solid sample of the capsule in a fullerene containing solution. Strikingly, the larger nanocapsule is shown to be effective for the selective separation of C60 from a mixture of fullerenes using a straightforward washing protocol of a solid sample of fullerene containing nanocapsule. Nowadays, the applications of fullerenes (i.e. in solar cells or in medicine) are limited in origin by their purification which is often tedious and expensive. The results of this investigation may pave the way for the future development of new methodologies for the purification of fullerene mixtures. Finally, the confined inner cavity of the larger nanocapsule, 2, was used to encapsulate a chiral rhodium catalyst which gave amongst the highest selectivities in the asymmetric hydroformylation of styrene for a monoligated rhodium catalyst. The results obtained demonstrate a substantial increase in stereoselectivity upon encapsulation of the catalyst, providing evidence of a selectivity-inducing effect by the secondary coordination sphere reminiscent of enzymatic active sites. ​
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