TRR 325:  Assembly Controlled Chemical Photocatalysis

• Subject Area: Chemistry
• Term: since 2021
• Website: Homepage
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 444632635

The goal of chemical photocatalysis is to create new structures and explore novel reactions by capturing light, ideally visible light. The dramatic advancements in the field over the past ten years have transformed organic synthesis. Light-driven reactions facilitate the generation of reactive intermediates, which are key components in bond-forming events. The selectivity and productivity of photocatalytic transformations depend significantly on the interactions between the substrate and the catalytically active species before, during, and after light excitation. However, for most reported photocatalytic and photochemical reactions, these interactions are ill-defined or unknown. This CRC aims to explore new frontiers in photocatalysis for organic synthesis through the designed control of catalyst-substrate interactions. The results of this research initiative will enable the broader application of light-initiated chemical transformations as essential tools for the selective and efficient synthesis of complex molecules in academic research and industrial production. The interdisciplinary research approach combines experimental, spectroscopic, and computational techniques to analyze and apply various catalyst-substrate interactions, including reversible coordination and reversible covalent bonding, hydrogen bonding, ionic and dipolar interactions, London forces, and solvation. During the first funding period, the CRC established itself as one of the most active research hubs in the field of chemical photocatalysis. Collaborative research endeavors have led to the identification of key interactions responsible for assembly control in photocatalysis. Building on the CRC's success, activities in the second funding period aim to leverage pivotal results from the first funding period and expand the diversity of the covered science. This will involve incorporating new spectroscopic techniques into the CRC and broadening expertise, particularly by integrating three additional Principal Investigators specializing in quantum-chemical calculations and machine learning.

• DFG Programme: CRC/Transregios

Current projects

• A01 - Visible Light Mediated Coupling Reactions via Photoexcitation of Earth-Abundant Metal-Substrate Assemblies: Regio- and Stereoselective C,H-Activation by Directed HAT Processes (Project Head Reiser, Oliver )
• A02 - Light-Induced Homolysis (LIH) of 3d-Metal-Substrate Complexes as a Starting Point for Organic Reactions (Project Head Reiser, Oliver )
• A03 - Photocatalysis with Reversibly Coordinating Metal Complexes (Project Head König, Burkhard )
• A04 - Preassembly Effects in the Photochemistry 3d Transition Metal Complexes and Synthetic Phosphorus Chemistry (Project Head Wolf, Robert )
• A05 - Monitoring and Exploiting Short-Lived Intermediates in Assembly-Controlled Photocatalytic Processes (Project Head Nürnberger, Patrick )
• A06 - Interrogating Radical Intermediates with Time-Resolved EPR (TR-EPR) (Project Heads Nürnberger, Patrick ;  Rehbein, Julia )
• A07 - Bimetallic Photocatalyst Assemblies (Project Head Hess, Corinna )
• A08 - Ab Initio Modeling of Time-Resolved Spectra of Photoactive Assemblies (Project Head Tapavicza, Enrico )
• B01 - Chromophore Activation by Lewis Acid Coordination (Project Head Bach, Thorsten )
• B02 - Hydrogen Bonds and Ion Pairs in Enantioselective Photochemistry (Project Head Bach, Thorsten )
• B04 - Selenium Photo-π-Acid Catalysis (Project Head Breder, Alexander )
• B06 - Selective Bond Activation by Modulation of Proton-Coupled Electron Transfer (PCET) and Hydrogen Atom Transfer (HAT) (Project Head Zeitler, Kirsten )
• B07 - Radical Generation with Semiquinoid Flavin Catalysts and their Ring-Contracted Analogues (Project Head Storch, Golo Trutz Benjamin )
• B08 - Proving Pre-Association by Transient Spectroscopy on Multiple Timescales (Project Head Hauer, Jürgen )
• B09 - Quantum-Chemical Prediction of Enantioselectivity in Photocatalytic Transformations (Project Head Stein, Christopher J. )
• C01 - Taming Reactive Intermediates in Photocatalysis by Assembly Control (Project Head König, Burkhard )
• C02 - Analysis of Charge Transfer Complexes, Radcical Ion-Pairs and Photoatalytic Assemblies by NMR Spectroscopy (Project Head Gschwind, Ruth M. )
• C03 - Photocatalytic Csp2-Functionalizations in Confined Space (Project Head Gulder, Tanja )
• C05 - Development and Application of Novel Quantum-Chemical Excited-State Methods for the Accurate Description of Photocatalytic Processes (Project Heads Ochsenfeld, Christian ;  de Vivie-Riedle, Regina )
• C06 - Design and Directed Evolution of Artificial Photoenzymes (Project Head Zeymer, Cathleen )
• C07 - Machine Learning Insights into Catalyst-Substrate Assemblies for Rational Design (Project Head Westermayr, Julia )
• MGK - IRTG - Intermolecular Interactions Controlling Photocatalysis (Project Head König, Burkhard )
• Z - Central Administrative Project (Project Heads Bach, Thorsten ;  König, Burkhard )

Completed projects

• B03 - NMR spectroscopic tools to detect Brønsted/Lewis acid-base preorganization in photocatalysis (Project Head Gschwind, Ruth M. )
• B05 - Tuning Radical Reactivity in Photocatalytic Transformations of NHC-Activated Substrates (Project Head Rehbein, Julia )

• Applicant Institution: Universität Regensburg
• Co-Applicant Institution: Technische Universität München
• Participating University: Ludwig-Maximilians-Universität München; Universität Leipzig; Universität des Saarlandes
• Spokespersons: Professor Dr. Thorsten Bach, until 12/2025; Professor Dr. Burkhard König, since 1/2026