ChirAl PlasmOnic Nano-structures as Enantioselective photocatalysts – CAPONE

In view of the increasing demand for fine chemicals in many industrial sectors such as pharmacology or agrochemistry, the development of enantioselective chemistry is of paramount importance. Chiral separation is nowadays the industrial strategy of choice, while asymmetric catalysis is the best approach leading to the formation of enantiopure molecules. Even though the use of light as an energy source is well established in photocatalysis, little is known about its implementation in heterogeneous asymmetric reactivity in this field. Therefore, there is an urgent need to find new strategies to drive efficient asymmetric photochemical reactions with visible and NIR photons. In the CAPONE project we propose to combine the unique features of plasmonic photocatalysis with asymmetric reactivity, aiming at performing heterogeneous and asymmetric photocatalytic reactions driven by plasmons. In homogeneous catalysis, two main strategies have been developed to attain asymmetric reactivity: i) the use of a single bifunctional chiral photocatalyst (at the same time the chirality source and catalytic center) and ii) the implementation of a dual approach, in which two complementary catalysts with different functionalities work synergically in order to attain enantioselective control. These two approaches currently in place for the generation of stereocontrol in photochemical transformations driven by molecular catalysts have been our inspiration for the development of CAPONE in order to create heterogeneous and enantioselective photocatalytic systems activated by plasmonic excitation.
Two chiral plasmonic systems with chiroptical responses at different energy scales (from the UV to the NIR) will be used as starting materials: (1) chiral colloidal assemblies of plasmonic nanoparticles and (2) plasmonic nanowires assembled via a bottom-up approach into a multi-layered chiral structure. These two highly versatile plasmonic systems will be used to explore the two complementary strategies: the enantioselectivity of a plasmonic chiral surface by means of a bifunctional heterogeneous photocatalyst and that obtained when a catalyst (asymmetric or not) is introduced within the chiral plasmonic assembly. The fundamental question that CAPONE will address consists in understanding the nature of the interaction between light, the heterogeneous photocatalyst and the molecular species in order to master the stereocontrol of a photochemical reaction. This topic resonates strongly with the current need for cheap and reliable access to asymmetric transformations at the industrial scale.