Photoredox Catalysis in Aqueous Media by Well-defined Micellar Nanoreactors

• Applicant: Afshin Nabiyan, Ph.D.
• Subject Area: Polymer Materials
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 506620588

Despite many chemical reactants often reveal a low aqueous solubility in water, nature could perform all kinds of their chemical transformations reactions in water. Recently, catalysis by organic photoredox materials has emerged as a new and powerful strategy in synthetic organic chemistry to perform a wide variety of transformations. However, performance and extending the substrate scope of them in the aqueous phase is an extremely difficult task. Consequently, the main focus of this project is to construct organophotoredox active micelles that can facilitate catalysis in water under visible light irradiation. Especially the ability to perform organic reactions in aqueous media together with effective recycling strategies for catalysts will be the aim of this project to represent a keystone towards sustainable and green chemistry. Hereby, acridinium molecules as a promising candidate for organophotoredox catalyst will be loaded into the micellar core of polypeptoid block copolymer micelles. Poly(N-substituted glycines) (i.e., polypeptoids) are biocompatible, synthetically accessible, chemically and enzymatically stable, chemically diverse, and structurally controllable. Defined side-chain modification of them and choosing the sequence of the monomers in their copolymers allows the straightforward engineering and determination of the solution properties. Thereby, the catalytic active micellar system of them will be tuned and examined for direct C−H cyanation of aromatic compounds, the nucleophilic substitution of unactivated fluoroarenes, and ipso amination of alkoxyarenes. Noticeably, the scaffold of the micellar system will be reinforced by covalent crosslinking of the core or shell which leads to the high stability of the overall system against external stimuli and harsh reaction conditions such as pH, temperature, and additives. However, these approaches also will provide us several other benefits including adjusting the interaction in the core, better protection of photoredox units from deactivation and leaching, recovery of the catalysts, and presumably improving the transportation and diffusion of the reactants between hydrophobic and hydrophilic domains. The project will also address several fundamental barriers in organic photoredox reactions in the water regarding catalytic activity, efficiency, and stability. In more detail, increasing the lifetime of photoredox reactions, protecting active sites from decomposition, reduces the time of reactions, and preventing the photoredox catalysts from aggregation and precipitation.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Helmut Schlaad