Adding <sup>161</sup>Dy-Mössbauer spectroscopy to a multitechnique investigation of magnetic transitions in a {Co<sup>III</sup><sub>3</sub>Dy<sup>III</sup><sub>3</sub>} Single-Molecule Toroic.

Peng, Yan; Braun, Jonas; Scherthan, Lena; Auerbach, Hendrik; Wolny, Juliusz A; Schulze, Michael; Alp, E Ercan; Zhao, Jiyong et al. · Nat Commun · 2026

basic_science · Level V

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Abstract

The determination of the orientations of the individual Dy<sup>III</sup> anisotropy axes in polynuclear complexes is challenging but crucial for the understanding of systems showing Single Molecule Magnet or Single Molecule Toroic behavior. In particular, the experimental proof of a toroidal ground state from magnetization data often remains ambiguous. Here, we report the coordination cluster [Co<sup>III</sup><sub>3</sub>Dy<sup>III</sup><sub>3</sub>(µ<sub>3</sub>-OH)<sub>4</sub>(O<sub>2</sub>C-C<sub>6</sub>H<sub>4</sub>-p-Me)<sub>6</sub>(pmide)<sub>3</sub>(H<sub>2</sub>O)<sub>3</sub>]Cl<sub>2</sub> · 10MeCN (1) (H<sub>2</sub>pmide = N-2-pyridylmethyldiethanolamine) which crystallizes with threefold symmetry and contains an equilateral Dy<sup>III</sup><sub>3</sub> triangle surrounded by a triangle of diamagnetic Co<sup>III</sup> ions. We also report a multi-technique investigation of its toroidal magnetic spin structure, including <sup>161</sup>Dy Synchrotron Mössbauer Spectroscopy which shows an abrupt transition from a non-magnetic to a magnetic state. The experimental orientations of the individual Dy<sup>III</sup> magnetic axes were assessed using torque magnetometry and micro-SQUID measurements and both experiments converged on a spin structure that is in very good agreement with ab initio calculations. Such a multi-technique approach, including <sup>161</sup>Dy Synchrotron Mössbauer Spectroscopy, provides a roadmap for the unambiguous identification of such toroidal states.