Tetraoxolene-bridged rare-earth complexes: a radical-bridged dinuclear Dy single-molecule magnet. Issue 41 (29th August 2019)

• Record Type: Journal Article
• Authors: Reed, William R.; Dunstan, Maja A.; Gable, Robert W.; Phonsri, Wasinee; Murray, Keith S.; Mole, Richard A.; Boskovic, Colette
• Is Part Of: Dalton transactions. Volume 48:Issue 41(2019)
• Page Start: 15635
• Page End: 15645
• Publication Date: 2019-08-29
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c9dt01320b
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : A radical bromanilate-bridged dinuclear Dy(iii ) complex exhibits improved single-molecule magnet performance over the parent compound with a diamagnetic bridge. Abstract : Two families of neutral tetraoxolene-bridged dinuclear rare earth complexes of general formula [((HBpz3 )2 RE)2 (μ-tetraoxolene)] (RE = Y and Dy; HBpz3 − = hydrotris(pyrazolyl)borate; tetraoxolene = fluoranilate (fa 2− ; 1-RE ) or bromanilate (ba 2− ; 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 )2 RE)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.