SAMOP 2021 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 3: Chirality
MO 3.2: Vortrag
Dienstag, 21. September 2021, 11:15–11:30, H3
Chiral control of spin-crossover dynamics in Fe(II) complexes — •Malte Oppermann1, Francesco Zinna2,3, Jérôme Lacour3, and Majed Chergui1 — 1École Polytechnique Fédérale de Lausanne, Switzerland — 2Università di Pisa, Italy — 3Université de Genève, Switzerland
Fe(II)-based spin-crossover (SCO) complexes hold tremendous promise as multifunctional switches in molecular devices. However, real-world technological applications require the excited spin-states to be kinetically stable - a feature that has thus far only been achieved at cryogenic temperatures. In this respect, Fe(II)(bpy)3 has emerged as a prototypical model system in support of a single reaction coordinate model, where the back-SCO is governed by a symmetric stretching mode of the metal-ligand bonds, preserving the chiral configuration of the complex. Through a newly developed ultrafast circular dichroism technique combined with transient absorption and anisotropy measurements on Fe(II)(4,4’-dimethyl-2,2’-bpy)3 in solution, associated for stereocontrol with enantiopure TRISPHAT anions, we now show that this picture is incomplete: the decay of the photoexcited high-spin (HS) state is accompanied by ultrafast changes of its optical activity, reflecting the coupling to a symmetry-breaking torsional twisting mode. Moreover, we show that the ion-pairing interaction with the enantiopure anions suppresses the vibrational population of this mode, thereby achieving a four-fold extension of the HS lifetime. This novel strategy may thus significantly improve the kinetic stability of Fe(II)-based magnetic switches at room temperature.