Tetraoxolene-bridged rare-earth complexes: a radical-bridged dinuclear Dy single-molecule magnet
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Date
2019-08-22
Journal Title
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Publisher
Royal Society of Chemistry
Abstract
Two families of neutral tetraoxolene-bridged dinuclear rare earth complexes of general formula [((HBpz3)2RE)2(μ-tetraoxolene)] (RE = Y and Dy; HBpz3− = hydrotris(pyrazolyl)borate; tetraoxolene = fluoranilate (fa2−; 1-RE) or bromanilate (ba2−; 2-RE)) have been synthesised and characterised. In each case, the bridging tetraoxolene ligand is in the diamagnetic dianionic form and each rare earth metal centre has two HBpz3− ligands completing the coordination. Electrochemical studies on the soluble 2-RE family reveal a tetraoxolene-based reversible one-electron reduction. Bulk chemical reduction with cobaltocene affords the cobaltocenium (CoCp+) salt of the 1e-reduced analogue: [CoCp][((HBpz3)2RE)2(μ-ba˙)] (3-RE) that incorporates a radical trianionic form of the bromanilate bridging ligand. Alternating current (ac) magnetic susceptibility studies of 2-Dy reveal slow magnetic relaxation only in the presence of an applied magnetic field, but reduction to radical-bridged 3-Dy affords frequency-dependent peaks in the out-of-phase ac susceptibility in zero applied field. Exchange coupling between the Dy(III) ions and the radical bridging ligand thus reduces zero-field magnetisation quantum tunnelling and confers single-molecule magnet status on the complex. Comprehensive analysis of the magnetic relaxation data indicates that a combination of Orbach, Raman and direct relaxation processes are required to fit the data for both dysprosium bromanilate complexes. © Royal Society of Chemistry 2024.
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Keywords
Molecules, Magnets, Rare earths, Synthesis, Magnetic fields, Electrochemistry, Ligands, Raman spectroscopy
Citation
Reed, W. R., Dunstan, M. A., Gable, R. W., Phonsri, W., Murray, K. S., Mole, R. A., & Boskovic, C. (2019). Tetraoxolene-bridged rare-earth complexes: a radical-bridged dinuclear Dy single-molecule magnet. Dalton Transactions, 48(41), 15635-15645. doi:10.1039/C9DT01320B