PhD in organic chemistry (M/F) – Plasmon Activated molecular catalysis: application to orthogonal relay catalysis

Orthogonal relay catalysis is a relevant strategy for synthesizing high-value molecules for the pharmaceutical, agrochemical, and fragrance industries. This methodology allows the transformation of simple raw materials into complex products through multiple reactions within a single reactor. By eliminating the step of isolating intermediates, this method can overcome the challenges encountered in multi-step individual reactions (long reaction times, waste production, and high costs). Despite its advantages, orthogonal relay catalysis faces several challenges. Indeed, when multiple catalysts are mixed in the same reactor, interactions between the catalysts and intermediates can lead to reduced or zero efficiency, resulting in low turnover numbers (TON) and turnover frequencies (TOF), which are crucial indicators of catalyst efficiency and lifespan. 

The aim of this projet is to propose a new strategy to address these challenges. This approach involves the immobilization of two different catalysts onto a substrate made of gold nanorod (Au NR) networks. The catalysts can be "turned on/off" with a simple light stimulus. The key to this control lies in the polarization of light. By adjusting the polarization—either along the transverse or longitudinal axes of the AuNRs—the catalysts and associated processes will be selectively activated or deactivated. This will avoid unwanted interactions between catalysts, and the heterogenization of these catalysts will solve the recycling issues.

Selective immobilization of the two catalysts on the hot spots of the AuNR networks will be achieved by plasmon-assisted reduction of arylic diazonium salts. This grafting strategy offers several advantages: i) the presence of covalent Au-C bonds between the surface and the organic coating, promoting stable interfacial connections, (ii) spatial confinement of the catalysts in the hot spot regions around the nanoparticles, i.e., the regions of maximum plasmonic field enhancement, and (iii) the presence of para-functional groups available for post-functionalization. By employing this strategy, it will be possible to synthesize versatile and highly sought-after synthons, such as indoles and quinolines, which are widely used in various industries and possess significant biological activity. These valuable molecules will be synthesized using reactions such as the Sonogashira cross-coupling combined with hydroamination, or the Heck coupling followed by intramolecular cyclization.

More specifically, during the thesis, the PhD student will synthesize molecular complexes for grafting onto lithographically patterned gold networks. The entire system will then be used in molecular catalysis reactions under light irradiation, selecting the appropriate light polarization to turn on or off one of the catalysts.