Project Details
Projekt
3d-Metal Talk – Merging Iron Spin Crossover and Chromium Luminescence
Subject Area
Inorganic Molecular Chemistry - Synthesis and Characterisation
Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
Term
since 2025
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 561088918
Molecular transition metal complexes, in particular iron(II) spin-crossover (SCO) complexes, are ideal building blocks to develop spin-state switches in a bottom-up strategy for future applications in data storage, spintronics or quantum computation. However, optical readout and optical manipulation remains challenging. Molecular rubies, i.e. chromium(III) complexes with specifically tailored ligand fields, possess sharp spin-flip (SF) luminescence bands with high quantum yields. An attractive scenario for a switchable magnetic material with optical read-out is thus to combine SF luminescent molecular rubies with Fe(II) or Cr(II) SCO complexes in a molecular level, where the switched state can be read out either via classical probing of magnetic properties or static and time-resolved luminescence measurements. By combining synthesis, (ultrafast) pump-probe and X-ray spectroscopies and quantum chemical analyses, we will systematically study filter, antenna, quenching, magnetic and mechanical effects on the switching and read-out properties of designed molecular SCO–SF assemblies. In addition to monitoring SF emission intensities, we will evaluate SF emission energies and lifetimes for read-out which may be more sensitive to spin state changes than emission intensity alone. Synthetic targets are SF emitters and SCO units based on molecular iron and chromium complexes that are assembled as ion pairs, ligand-bridged heterobimetallic complexes and mixed-valent chromium(III/II) salts. Their magnetic and spectroscopic properties will reveal SCO and responsive SF luminescence behavior. Excited state dynamics at short and long timescales will be probed by variable-temperature emission and transient absorption spectroscopy. Complementary X-ray spectroscopy characterization in the solid state and in solution will provide insights into the structural and electronic evolution over the SCO curve and the influence of the Fe spin-state on the Cr excited state dynamics. Quantum chemical studies will focus on structural influences and temperature effects on these properties in representative ensembles, and develop a proof-of-concept for extending a recently proposed ab initio approach for quantifying Marcus–Hush theory to excitation energy transfer mechanisms. By strategically combining expertise in synthesis, advanced spectroscopy and quantum chemistry, we expect that this project will deliver molecular SCO–chromophore assemblies where the SCO spin population can be determined with high contrast using different read-out channels of the SF emitter.
DFG Programme
Priority Programmes
Subproject of
SPP 2491:
Interactive Spin-State Switching
