To ascertain if the chiroptical properties of enantiomerically pure, homoleptic Fe(II) SCO complexes correlate with the actual spin state, a series of optically active monodentate and bidentate (bridging) N1-substituted tetrazole ligands and their Fe(II) complexes were investigated. In the case of the monodentate system (fig.1) no difference in the temperature-dependent magnetic susceptibility of the S, R and rac-isomer Fe(II) complexes was observed. A different behavior is found in the case of the bidentate system, were S,S and R,R display the same crossover behavior and the meso-form different spin crossover behavior (fig. 2). To establish a correlation between spin-state and optical activity, allowing for a chiroptical determination of the spin state, the materials were analyzed by chiroptical methods. In the electronic spectra of the compounds, the direct correlation between the chiroptical information and the Fe(II) spin state became apparent. Quantum chemical calculations were used to support and verify the experimentally observed effect. In addition, the chiral SCO materials were deposited as monomolecular layer on a gold substrate. The contribution highlights how enantiomerically pure, chiral ligands may enable a novel non-destructive assessment of the spin-state in Fe(II)-SCO materials.

Chirality as key for determining the spin-state in Fe(II) spin crossover complexes

2019 Spring National Meeting

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