Photoinduced dynamics in bipyridylruthenium(II)-complexes: Investigation of activation and dissociation mechanisms by a combined approach of chemical synthesis and ultrafast spectroscopy in both gas phase and solution.

• Applicants: Professor Dr. Rolf Diller; Privatdozent Dr. Christoph Riehn; Professor Dr. Werner R. Thiel
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: from 2017 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 328137893

The rich photophysics and photochemistry of Ru(II)-complexes offers a huge potential for applications in technology and medicin. However, important relationships between the chemical constitution of the complexes and specific elementary steps of their photoactivation are not fully understood. This includes the impact of the ligands and their substituents on the energetics and the coupling of the relevant electronic states that, in turn, determine the quantum yield of functionally important physical (e. g. luminescence) and chemical (e.g. dissociation or ligand exchange) processes. Our proposal provides a combined approach of chemical synthesis, femtosecond time resolved spectroscopy and quantum chemical calculations, aiming at filling existing gaps in the current level of knowledge and leading to a deeper understanding. Thus the conceptional strength of the proposal is given by the coordinated efforts of: 1. Chemical synthesis of bipyridyl-ruthenium(II)-complexes with systematic variation of ligands, substituents and solvation. Thereby specific physicochemical parameters can be tuned. This includes the energetics of the participating electronic states, the (optical) antenna properties, implementation of spectroscopic "markers" for tracking specific processes as well as solubility. 2. Femtosecond time-resolved spectroscopy in both gas phase (i) and in solution phase (ii). This allows first (i) sensitive detection of photoinduced dissociation, access to intrinsic Ru(II)-complex properties and better comparability with results of quantum chemical (vacuum-) calculations, and second (ii) the investigation of electronic (UV/Vis/NIR) and structural (mid-IR) dynamics as well as the identification of processes and intermediate states under solution-phase (i. e. more realistic) conditions. 3. Accompanying quantum chemical calculations in order to better assess trends in electronic state energies upon variation of ligands and substituents and to support the interpretation of the experimental results. Furthermore, the calculations are used (where practicable) in connection with transient IR- and IRMPD-spectra for structural elucidation of intermediate states and species.

• DFG Programme: Research Grants