Uncovering ultrafast dynamics and coherence in next-generation sustainable Earth-abundant metal complexes

• Applicant: Dr. Winald Robert Kitzmann
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry ; Inorganic Molecular Chemistry - Synthesis and Characterisation
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 544956268

Light is the central component in optical sensing, photovoltaics and photocatalysis. These technologies require a molecule that captures energy and stores it for long enough to drive the desired processes. Transition metal complexes can perform both these tasks and thus are promising sensitizers for these applications. In particular, complexes of precious metals exhibit long-lived electronic excited states that store energy. As a result, research has focused on this class of compounds, yet the low abundance of the metals limits their use at industrial scale. In contrast, complexes of earth-abundant metals typically show short-lived excited states, and so to date lack the required performance for these technologies. The goal of this project is to establish a new design strategy for transition metal complexes based on earth-abundant iron and cobalt by selectively shifting the energies of deactivating electronic states. This will be achieved by synthesizing new complexes combining strong-field cyanide and polypyridine ligands in a favorable tripodal coordination geometry. When the proposed strategy was applied to isoelectronic molybdenum(0) complexes, the excited state lifetime was prolonged by a factor of 500. The energetic shifts, the dynamics after light absorption, and their interplay will be quantified through state-of-the-art time-resolved spectroscopy. The results will provide fundamental insights into the electronic manifold of these compounds and guide to molecular optimization. In particular, ultrashort laser pulses will reveal coherences that directly report on the elusive connection between photophysical transformations and molecular motions. The proposed combination of molecular design and powerful spectroscopic methods will further our understanding of iron and cobalt chromophores and pave the way for the earth-abundant metal complexes required for sustainable light-driven applications.

• DFG Programme: WBP Fellowship
• International Connection: USA
• Host: Professorin Dr. Gabriela S. Schlau-Cohen