How electron spin coupling affects catalytic oxygen activation
A team at the EPR4Energy joint lab of HZB and MPI CEC has developed a new THz EPR spectroscopy method to study the catalytic activation of molecular oxygen by copper complexes. © T. Lohmiller/HZB
A team at the EPR4Energy joint lab of HZB and MPI CEC has developed a new THz EPR spectroscopy method to study the catalytic activation of molecular oxygen by copper complexes. The method allows insights into previously inaccessible spin-spin interactions and the function of novel catalytic and magnetic materials.
Molecular oxygen (O2) is a preferred oxidant in green chemistry. However, activation of O2 and control of its reactivity requires precise adjustment of the spin states in the reactive intermediates. In nature, this is achieved by metalloenzymes that bind O2 at iron or copper ions, and spin-flip processes are enabled through metal-mediated spin-orbit couplings allowing for mixing of states. In the case of type III dicopper metalloproteins involved in oxygen transport and oxygenation of phenolic substrates, little was known about the pathway leading to a dicopper peroxo key species with a stabilized singlet ground state after triplet oxygen binding.
Through a sophisticated ligand design, the research group led by Prof. Franc Meyer at the University of Göttingen has now succeeded in isolating a series of model complexes that mimic the initial stage of oxygen binding at dicopper sites and exhibit a triplet ground state. Researchers from the EPR4Energy joint lab of HZB and MPI CEC complemented this breakthrough in chemical synthesis with a new approach of THz-EPR spectroscopy. This method, developed in Alexander Schnegg's group at MPI CEC, was applied for the first time to study the function-determining antisymmetric exchange in coupled dicopper(II) complexes.
The new method allowed for detection of the entirety of spin state transitions in the system, which leads to propose antisymmetric exchange as an efficient mixing mechanism for the triplet-to-singlet intersystem crossing in biorelevant peroxodicopper(II) intermediates. Thomas Lohmiller, one of the first authors of the study, explains, "In addition to the knowledge gained about this important system, our method opens up the possibility of studying previously inaccessible spin-spin interactions in a variety of novel catalytic and magnetic materials."
- Breakthrough at HZB: First electron beam in SEALab advances accelerator physicsThe SEALab team at HZB has achieved a world first by generating an electron beam from a multi-alkali (Na-K-Sb) photocathode and accelerating it to relativistic energies in a superconducting radiofrequency accelerator (SRF photoinjector). This is a real breakthrough and opens up new options for accelerator physics.
- Optical innovations for solar modules - which are the most promising?In 2023, photovoltaic systems generated more than 5% of the world’s electrical energy and the installed capacity doubles every two to three years. Optical technologies can further increase the efficiency of solar modules and open up new applications, such as coloured solar modules for facades. Now, 27 experts provide a comprehensive overview of the state of research and assess the most promising innovations. The report, which is also of interest to stakeholders in funding and science management, was coordinated by HZB scientists Prof. Christiane Becker and Dr. Klaus Jäger.
- Catalysis research with the X-ray microscope at BESSY IIContrary to what we learned at school, some catalysts do change during the reaction: for example, certain electrocatalysts can change their structure and composition during the reaction when an electric field is applied. The X-ray microscope TXM at BESSY II in Berlin is a unique tool for studying such changes in detail. The results help to develop innovative catalysts for a wide range of applications. One example was recently published in Nature Materials. It involved the synthesis of ammonia from waste nitrates.