Single-Ion Magnetic Behaviour in an Iron(III) Porphyrin Complex: A Dichotomy Between High Spin and 5/2–3/2 Spin Admixture |
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| Authors: | Dr Marta Viciano-Chumillas Dr Geneviève Blondin Dr Martin Clémancey Dr Jurek Krzystek Dr Mykhaylo Ozerov Prof?Dr Donatella Armentano Dr Alexander Schnegg Dr Thomas Lohmiller Prof?Dr Joshua Telser Prof Francesc Lloret Dr Joan Cano |
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| Institution: | 1. Institut de Ciència Molecular (ICMol), Universitat de València, 46980 Paterna, Spain;2. CNRS, CEA, IRIG, CBM, Université Grenoble Alpes, CEA-Grenoble, 38000 Grenoble, France;3. National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, 32310 USA;4. Dipartimento di Chimica e Tecnologie Chimiche (CTC), Università della Calabria, 87030 Rende, Cosenza, Italy;5. EPR Research Group, MPI for Chemical Energy Conversion, Stiftstrasse 34–36, 45470 Mülheim Ruhr, Germany;6. EPR4Energy Joint Lab, Department Spins in Energy Conversion and Quantum Information Science, Helmholtz-Zentrum Berlin für Materialien und Energie, Kekuléstrasse 5, 12489 Berlin, Germany;7. Department of Biological, Physical and Health Sciences, Roosevelt University, 430 S. Michigan Avenue, Chicago, IL, 60605 USA |
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| Abstract: | A mononuclear iron(III) porphyrin compound exhibiting unexpectedly slow magnetic relaxation, which is a characteristic of single-ion magnet behaviour, is reported. This behaviour originates from the close proximity (≈550 cm?1) of the intermediate-spin S=3/2 excited states to the high-spin S=5/2 ground state. More quantitatively, although the ground state is mostly S=5/2, a spin-admixture model evidences a sizable contribution (≈15 %) of S=3/2 to the ground state, which as a consequence experiences large and positive axial anisotropy (D=+19.2 cm?1). Frequency-domain EPR spectroscopy allowed the mS= |±1/2?→|±3/2? transitions to be directly accessed, and thus the very large zero-field splitting in this 3d5 system to be unambiguously measured. Other experimental results including magnetisation, Mössbauer, and field-domain EPR studies are consistent with this model, which is also supported by theoretical calculations. |
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| Keywords: | density functional calculations iron porphyrinoids magnetic properties single-ion magnets |
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