Strong Electronic and Magnetic Coupling in M4 (M = Ni, Cu) Clusters via Direct Orbital Interactions between Low-Coordinate Metal Centers
| Autor: | Khetpakorn Chakarawet, Jeffrey R. Long, Frank Neese, Mihail Atanasov, Jonathan Marbey, Stephen Hill, Philip C. Bunting |
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| Rok vydání: | 2020 |
| Předmět: |
Magnetism
Chemistry Relaxation (NMR) General Chemistry Electronic structure Orbital overlap 010402 general chemistry 01 natural sciences Biochemistry Molecular physics Catalysis 0104 chemical sciences Delocalized electron Magnetic anisotropy Colloid and Surface Chemistry Ferromagnetism Cluster (physics) Condensed Matter::Strongly Correlated Electrons |
| Zdroj: | Journal of the American Chemical Society. 142:19161-19169 |
| ISSN: | 1520-5126 0002-7863 |
| Popis: | We present an extensive study of tetranuclear transition-metal cluster compounds M4(NPtBu3)4 and [M4(NPtBu3)4][B(C6F5)4] (M = Ni, Cu; tBu = tert-butyl), which feature low-coordinate metal centers and direct metal-metal orbital overlap. X-ray diffraction, electrochemical, magnetic, spectroscopic, and computational analysis elucidate the nature of the bonding interactions in these clusters and the impact of these interactions on the electronic and magnetic properties. Direct orbital overlap results in strongly coupled, large-spin ground states in the [Ni4(NPtBu3)4]+/0 clusters and fully delocalized, spin-correlated electrons. Correlated electronic structure calculations confirm the presence of ferromagnetic ground states that arise from direct exchange between magnetic orbitals, and, in the case of the neutral cluster, itinerant electron magnetism similar to that in metallic ferromagnets. The cationic nickel cluster also possesses large magnetic anisotropy exemplified by a large, positive axial zero-field splitting parameter of D = +7.95 or +9.2 cm-1, as determined by magnetometry or electron paramagnetic resonance spectroscopy, respectively. The [Ni4(NPtBu3)4]+ cluster is also the first molecule with easy-plane magnetic anisotropy to exhibit zero-field slow magnetic relaxation, and under a small applied field, it exhibits relaxation exclusively through an Orbach mechanism with a spin relaxation barrier of 16 cm-1. The S = 1/2 complex [Cu4(NPtBu3)4]+ exhibits slow magnetic relaxation via a Raman process on the millisecond time scale, supporting the presence of slow relaxation via an Orbach process in the nickel analogue. Overall, this work highlights the unique electronic and magnetic properties that can be realized in metal clusters featuring direct metal-metal orbital interactions between low-coordinate metal centers. |
| Databáze: | OpenAIRE |
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