150585 20260218074035.0 doi 10.1021/acs.inorgchem.4c04191 sideral 142677 ART-2024-142677 eng (orcid)0000-0002-6517-1236 Bartolomé, Juan Single-Molecule Magnet Behavior and Spin Structure of an Fe^III₇ Cartwheel Cluster Revealed by Sub-Kelvin Magnetometry and Mössbauer Spectroscopy: The Final Pieces of the Puzzle 2024 The spin frustration and other magnetic properties of the “cartwheel” heptanuclear cluster [FeIII7O3(O2CtBu)9(Me-dea)3(H2O)3] (Me-deaH2 = N-methyldiethanolamine) have been previously investigated; we present here a Mössbauer spectroscopic study and sub-Kelvin magnetization and ac susceptibility measurements which enable a complete magnetic picture of this frustrated cluster. 57Fe Mössbauer spectra above 150 K showed three doublets in a 1:3:3 ratio, which could be assigned by their respective quadrupole splittings to the central Fe(1) and the peripheral Fe(2) and Fe(3). The field dependence of the corresponding magnetic sextets at 3 K showed that the spins on the central Fe(1) and the three peripheral Fe(2) sites with O5N coordination are oriented mutually coparallel, while these are antiparallel to the spins on the peripheral Fe(3) sites with O6 coordination, resulting in an overall S = 5/2 ground state. This provides experimental confirmation of the previously proposed spin ground state structure. Upon cooling to sub-Kelvin temperatures, a crossover to spin blocking with TB ≈ 0.21 K could be observed. This single-molecule magnet behavior had been expected but had not been observable with a conventional SQUID. The anisotropy barrier, of 3-fold symmetry, can be described in terms of the parameter D/kB = −0.47 K and a fourth-order perturbation; the latter enables thermally activated quantum tunneling through the excited sublevel mz = ± 3/2, with an activation barrier of U/kB = 1.9 K. info:eu-repo/grantAgreement/ES/AEI/CEX2023-001263-S info:eu-repo/grantAgreement/ES/AEI/CEX2023-001286-S info:eu-repo/grantAgreement/ES/AEI/AEI PID2022-140923NB-C21 info:eu-repo/grantAgreement/ES/AEI/AEI PID2022-140923NB-C22 info:eu-repo/grantAgreement/ES/DGA/E09-17R-Q-MAD info:eu-repo/grantAgreement/ES/DGA-FSE/E12-23R-RASMIA info:eu-repo/grantAgreement/ES/MICINN-AEI/PRTR-C17.I1 info:eu-repo/grantAgreement/ES/MICINN/PID2022-138492NB-I00 info:eu-repo/semantics/openAccess All rights reserved http://www.europeana.eu/rights/rr-f/ 4.7 2024 CHEMISTRY, INORGANIC & NUCLEAR 6 / 43 = 0.14 2024 Q1 T1 0.958 2024 Chemistry (miscellaneous) 2024 Q1 Physical and Theoretical Chemistry 2024 Q1 Inorganic Chemistry 2024 Q1 7.4 2024 info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion Bartolomé, Elena (orcid)0000-0001-6284-0521 Luis, Fernando Burzurí, Enrique (orcid)0000-0001-7289-5649 Camón, Agustin Filoti, George Ako, Ayuk M. Braun, Jonas Mereacre, Valeriu Anson, Christopher E. Powell, Annie K. 63, 51 (2024), 24262-24273 Inorg. chem. Inorganic Chemistry 0020-1669 4433933 http://zaguan.unizar.es/record/150585/files/texto_completo.pdf Versión publicada info:eu-repo/date/embargoEnd/2025-12-08 3088450 http://zaguan.unizar.es/record/150585/files/texto_completo.jpg?subformat=icon icon Versión publicada info:eu-repo/date/embargoEnd/2025-12-08 oai:zaguan.unizar.es:150585 articulos driver 2026-02-17-20:46:37 ARTICLE