Photochemical Spin-State Switching using All-Organic Molecular Systems

• Applicant: Professor Dr. Oliver Dumele
• Subject Area: Organic Molecular Chemistry - Synthesis and Characterisation
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 575910851

This proposal explores a novel class of all-organic, light-responsive spin-state switches based on chiral [5]helicene scaffolds. Organic molecules capable of photochemically switching between diamagnetic and paramagnetic states represent a promising approach for future quantum information technologies. We aim to combine photo-induced spin switching with inherent molecular chirality, enabling access to chiroptical readouts and potentially spin-polarized or entangled states on a molecular level. Building on our recent discovery of a bistable spin-state switch via light-triggered ring-opening in a helicene derivative, we propose to expand the synthetic design space of such systems. Through tailored structural modifications - including radical-stabilizing substituents, π-extensions, and helicene backbone stretching - we seek to control bi-stability, thermal stability, and operational conditions such as wavelength and temperature. The project will combine advanced organic synthesis with spectroscopic and magnetic methods (UV/vis, EPR, SQUID, CPL) and quantum chemical calculations. Emphasis is placed on achieving reversible switching using visible light at accessible cryogenic temperatures (100-200 K), as well as on understanding the relationship between structure and spin-state energetics. Ultimately, we aim to establish design principles for light-controlled chiral diradicals and to lay the groundwork for their use in spin readout, chiral luminescence, and molecular quantum sensing. This interdisciplinary project addresses key challenges in molecular spintronics and organic photo-magnetism.

• DFG Programme: Research Grants