Project Details
Projekt
P3: Pseudo-octahedral 3d3 spin-flip emitters under pressure, strain and magnetic fields
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 535200000
The project of the present FOR aims to establish structure-property relationships for efficient reversible stimulus-responsive spin-flip (SF) emission from pseudo-octahedral d3-chromium(III) emitters of defined topologies based on structural and electronic effects as stimulus response to pressure (P), uniaxial strain (F), magnetic fields (B) and the presence of energy acceptors (A) and radicals (R). The energies of SF states subtly depend on the M-L distances, L-M-L angles and torsion angles in a manner that is only recently partially understood. A unique asset of the chromium(III) emitters is the paramagnetic nature of the ground and luminescent SF states, providing ample opportunities for external stimuli to affect the photonic response such as magnetic fields or the presence of other spin carriers. While some meridionally coordinated complexes have been studied under isotropic pressure, other topologies such as facially, tris(bidentate) or 4+2 coordinated (macrocyclic) complexes are underexplored, although these topologies are expected to enable different structural and hence photophysical responses to stimuli. The project addresses topology dependent photonic stimulus responsivity of SF states with ultralong lifetimes in luminescent chromium(III) complexes by ligand design. Stimuli comprise pressure, force, magnetic fields, presence of energy acceptors and radicals, and responses involve emission energy, lifetime, quantum yield, circularly polarized luminescence (CPL) for chiral variants and radiative/non-radiative rates. The complexes will be prepared and investigated regarding their photophysical properties and nature of the excited states in dependence of the coordination topology and chirality. The excited SF state ordering varies with the topology and will be systematically studied and elucidated in this project. Structural and spectroscopic characterization of the ground and excited states including X-ray diffraction, optical and vibrational spectroscopy, transient-EPR spectroscopy, transient absorption spectroscopy and X-ray absorption/emission spectroscopy without and with a stimulus is required to arrive at a structure-property relationship. Of particular interest are responses of the excited state dynamics to pressure or strain, chiral enhancement under pressure, the effects of Zeeman splitting of ground and excited states by magnetic fields on the dynamics, the spin polarization and the coupling of ground and excited states with radicals. This investigation includes the development of suitable spectroscopic tools and protocols under the stimuli in particular trEPR spectroscopy as developed in this project.
DFG Programme
Research Units
