Quantum mechanical tools for the prediction of the excited state properties of molecular multi-spin systems

• Applicant: Professorin Dr. Sabine Richert
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry ; Theoretical Chemistry: Electronic Structure, Dynamics, Simulation
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 536668010

Photogenerated molecular triplet-doublet spin systems, composed of a chromophore and a covalently bound stable radical, have suitable properties to be used as components of molecular spintronic devices. Through excitation with light, an excited doublet state and a quartet state are generated, whereby their energy difference depends on the exchange interaction J-TR between the chromophore triplet state and the stable radical. To improve the design of these systems for future applications, it is of utmost importance to explore how spin communication can be optimized and controlled. Since the interaction between chromophore triplet state and radical is mainly governed by J-TR, we need to gain knowledge on how to control the magnitude and sign of this interaction parameter. Recently we were able to demonstrate that ab initio quantum chemical calculations can be used to predict reliable trends in J-TR and thus serve as a tool to guide the design of new spintronic materials. Here we will build on this work and devise new theoretical methodologies to identify the role of the symmetry of the molecular orbitals and its influence on the magnitude and sign of the individual exchange interactions contributing to J-TR. Finally, the reliability and accuracy of the newly developed theoretical methods and protocols will be evaluated by comparison with experimental data from transient electron paramagnetic resonance and femtosecond transient absorption measurements.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Frank Neese