Adding 161Dy-Mössbauer spectroscopy to a multitechnique investigation of magnetic transitions in a {CoIII3DyIII3} Single-Molecule Toroic

: The determination of the orientations of the individual DyIII 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 [CoIII3DyIII3(µ3-OH)4(O2C-C6H4-p-Me)6(pmide)3(H2O)3]Cl2 · 10MeCN (1) (H2pmide = N-2-pyridylmethyldiethanolamine) which crystallizes with threefold symmetry and contains an equilateral DyIII3 triangle surrounded by a triangle of diamagnetic CoIII ions. We also report a multi-technique investigation of its toroidal magnetic spin structure, including 161Dy Synchrotron Mössbauer Spectroscopy which shows an abrupt transition from a non-magnetic to a magnetic state. The experimental orientations of the individual DyIII 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 161Dy Synchrotron Mössbauer Spectroscopy, provides a roadmap for the unambiguous identification of such toroidal states.