Chiral Nanoclusters for Heterogeneous Asymmetric Catalysis

Chirality is omnipresent across the universe at different scales, from galaxies to atomic particles. But what is chirality? Let us take a look at our hands: they are chiral because the right hand is a mirror image of the left hand but they cannot be superimposed. We also find this feature in many molecules with right and left forms, called enantiomers, which can possess very different properties. Chirality is particularly critical in the pharmaceutical industry: one enantiomeric form of a drug may heal whereas the other one (the mirror drug) may be harmful (thalidomide was a tragic example). Thus, it is crucial to selectively produce one enantiomer of a compound. In the last decade, this was achieved by chiral homogeneous catalysts. However, homogeneous refers to catalysts and molecules sharing the same medium, requiring tedious separation or recycling, restricting its application for industry, which normally uses solid heterogeneous catalysts. Therefore, it is the time to undertake the challenge of obtaining pure enantiomers employing/using heterogeneous chiral catalysts. However, the successful design of such processes implies to understand and control every relevant step, requiring well-defined catalysts designed at atomic level. This can be achieved with metal nanoclusters, which exhibit unexpected and tuneable catalytic properties. A second challenge is to preserve the properties of the nanoclusters after their deposition on active support surfaces. Over the last years, we successfully developed heterogeneous nanocluster catalysts and were able to understand their behaviour at molecular level using spectroscopic techniques. Another outstanding property of these nanoclusters is their intrinsic chiral nature, which can also be induced by chiral ligands. This makes them the ideal candidates to overcome the challenge to extend nanocatalysis towards enantioselective reactions, which represents the goal of this project. After creating chiral clusters active in homogeneous asymmetric reactions, we will control their immobilization on the support surface and their chiral properties (proof of concept established in 2020). Such atomically precise chiral surfaces will permit to overcome sensitivity barriers of the available spectroscopic techniques, improving studies of chirality at surfaces. Finally, having a well- defined chiral surface, asymmetric/enantioselective model reactions will be explored, aiming to obtain pure enantiomers. Each process step represents by itself a novel pioneering work in the field of nanoclusters and asymmetric catalysis, so far mostly unexplored. Manufacturing and understanding such a new class of chiral surfaces at the atomic level will represent a knowledge breakthrough relevant for materials science, nanotechnology, biology and medicine.

Chirality, the property of objects being non-superimposable mirror images of each other, is critical in several fields, particularly the pharmaceutical industry, where enantiomers - mirror-image forms of a molecule - can have drastically different effects. The selective production of pure enantiomers is therefore essential. While homogeneous chiral catalysts have been effective in achieving this, their industrial use is limited due to separation and recycling challenges. To address this, our project focuses on designing chiral active centres with atomic precision and understanding their chirality for future application in heterogeneous chiral catalysts. The project has achieved significant milestones, starting with the synthesis of enantiomerically pure chiral nanoclusters that exhibited strong and stable chiral properties under harsh conditions. These clusters showed promising catalytic activity in homogeneous asymmetric reactions, providing a basis for their use in heterogeneous systems. A major achievement was to optimise the immobilisation of these clusters on active support surfaces, preserving their properties and allowing further functionalisation. This functionalisation endowed the clusters with new properties, extending their applications beyond chiral catalysis. The project also provided critical insights into the structural dynamics of clusters during catalytic reactions, enhancing our ability to design stable and effective catalysts. The immobilisation and functionalisation processes open up avenues for applications in materials science, nanotechnology and biology. This pioneering work advances research on nanoclusters and asymmetric catalysis, providing a platform for understanding and exploiting chirality at the atomic level. The results have broad implications for pharmaceuticals, materials science and nanotechnology.