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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 25: Bio- and Molecular Magnetism (joint session MA/CPP)

CPP 25.1: Vortrag

Montag, 16. März 2020, 15:00–15:15, HSZ 101

HF-EPR investigations on Co(II)- and Fe(IV)-coordination complexes — •Lena Spillecke¹, Changhyun Koo¹, Shalini Tripathi², Maheswaran Shanmugam², Saskia Krieg³, Peter Comba³, and Rüdiger Klingeler¹ — ¹Kirchhoff-Institut für Physik, Universität Heidelberg, Heidelberg, Germany — ²Department of Chemistry, Indian Institute of Technology, Mumbai, India — ³Institute of Inorganic Chemistry, Universität Heidelberg, Heidelberg, Germany

We present high-frequency/high-field electron paramagnetic resonance (HF-EPR) studies on Co(II) and Fe(IV) coordination complexes. For Co(II) systems, we show that ligand exchange in the 2nd coordination sphere on [Co(L₁)₄]X₂, with L₁ = thiourea (NH₂CSNH₂) and X = I (1),Br (2), SiF6 (3)) has significant effects on the crystal field and hence on magnetic anisotropy of the Co-ion. While the substitution of I by Br only has small impact on the axial anisotropy (D = -153(2)/-168(5) GHz, respectively), we observed strong enhancement of anisotropy in the SiF₆ containing sample (|D| > 800 GHz). Furthermore, our data enables precise determination of weak intermolecular coupling in the range of several hundred mK which sign changes by ligand substitution. In additon, we present HF-EPR data on an octahedrally coordinated Fe(IV)-complex which was prepared under liquid N₂ conditions. Our results confirm the intermediate-spin state and detect axial anisotropy of D= 107(3) GHz.