Towards Understanding Prolate 4$f$ Monomers: Numerical Predictions and Experimental Validation of Electronic Properties and Slow Relaxation in a Muffin-shaped Er${}^{\mathrm{III}}$ Complex

Abstract

We report the synthesis, crystal structure and magnetic properties of the triply-capped, slightly distorted trigonal-prismatic complex [Er(PPTMP)${}_2$(H${}_2$O)][OTf]${}_3$ (PPTMP = (4-(6-(1,10-phenanthrolin-2-yl)pyridin-2-yl)-1H-1,2,3-triazol-1-yl)methyl pivalate) ($1$). Complex $1$ is shown to exhibit field-induced slow relaxation of the magnetisation at $B=0.1\mathrm{T}$ via two distinct relaxation paths. Using tunable high-frequency/high-field electron paramagnetic resonance spectroscopy, we experimentally determine the effective $g$-factors and zero field splittings of the two energetically lowest Kramers doublets (KD). Our data reveal that the triply-capped, slightly distorted trigonal-prismatic ligand field favours an $m\simeq \pm 9/2$ magnetic ground state, while the main contribution to the first excited KD at ${\Delta }_{1\to 2}=780(5)\mathrm{GHz}$ is suggested to be $m\simeq \pm 5/2$. The ground state $g$-tensor has generally axial form but hosts significant transversal components, which we conclude to be the source of SMM-silent behaviour in zero field. Our findings are backed up by ab-initio spin-orbit configuration interaction calculations showing excellent agreement with the experimental data.

11 pages, 10 figures

References in corpus (2)

• The Interplay of Single Ion Anisotropy and Magnetic 3d-4f Interactions in V${}_2^{\mathrm{III}}$Ln${}_2^{\mathrm{III}}$ Butterfly Complexes
• The Relevance of Non-axiality and Low-lying Excited States for Slow Magnetic Relaxation in Pentagonal-bipyramidal Erbium(III) Complexes Probed by High-frequency EPR