Subcomponent Self-Assembly of Rare-Earth Single-Molecule Magnets (original) (raw)
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Molecular Magnets Based on Homometallic Hexanuclear Lanthanide(III) Complexes
Inorganic Chemistry, 2014
The reaction of lanthanide(III) chloride salts (Gd(III), Dy(III), Tb(III), and Ho(III)) with the hetero donor chelating ligand N′-(2-hydroxy-3-methoxybenzylidene)-6-(hydroxymethyl)picolinohydrazide (LH 3) in the presence of triethylamine afforded the hexanuclear Ln(III) complexes [{Ln 6 (L) 2 (LH) 2 }(μ 3-OH) 4 ][MeOH] p [H 2 O] q [Cl] 4 •xH 2 O• yCH 3 OH (1, Ln = Gd(III), p = 4, q = 4, x = 8, y = 2; 2, Ln = Dy(III), p = 2, q = 6, x = 8, y = 4; 3, Ln = Tb(III), p = 2, q = 6, x = 10, y = 4; 4, Ln = Ho(III), p = 2, q = 6, x = 10, y = 2). Xray diffraction studies revealed that these compounds possess a hexanuclear [Ln 6 (OH) 4 ] 14+ core consisting of four fused [Ln 3 (OH)] 8+ subunits. Both static (dc) and dynamic (ac) magnetic properties of 1−4 have been studied. Single-molecule magnetic behavior has been observed in compound 2 with an effective energy barrier and relaxation time pre-exponential parameters of Δ/k B = 46.2 K and τ 0 = 2.85 × 10 −7 s, respectively. ■ EXPERIMENTAL SECTION Reagents and General Procedures. Solvents and other general reagents used in this work were purified according to standard procedures. 13 Pyridine-2,6-dicarboxylic acid, sodium borohydride, DyCl
Molecular Design for Single-molecule Magnetism of Lanthanide Complexes
Chemistry Letters, 2017
Sunri Lee received her B.S. degree in chemistry from Osaka University in 2010. After receiving her M.Sc. degree from the University of Tokyo in 2012, she joined Prof. Ogawa's group at Osaka University to pursue her Ph.D. degree in organic chemistry. Her current research focuses on single-molecule magnets based on porphyrin multiple-decker complexes with lanthanide ions.
Dalton Transactions, 2014
= bis[(2-pyridyl)methylne]pyridine-2,6dicarbohydrazide and H 4 L 2 = bis[2-hydroxy-benzylidene]pyridine-2,6-dicarbohydrazide) are reported. Structural investigation by x-ray crystallography reveals similar structural features for complexes 1 and 2 and they exhibit butterfly like shape of the molecule. Non-covalent interactions between the molecules create double helical arrangements for both the molecules. Complexes 3 and 4 are iso-structural and the 15 core structures feature four distorted hemi-cubanes connected by vertex sharing . Magnetic studies unveil significant magnetic entropy changes for complexes 1, 3 and slow relaxation of magnetization for both the dysprosium analogues 2 and 4.
A Polynuclear Lanthanide Single-Molecule Magnet with a Record Anisotropic Barrier
Angewandte Chemie International Edition, 2009
Dedicated to Professor Annie K. Powell on the occasion of her 50th birthday Single-molecule magnets (SMMs) continue to be an attractive research field because of their unique and intriguing properties and potential applications in high-density data storage technologies and molecular spintronics. [1] The anisotropic barrier (U) of an SMM is derived from a combination of an appreciable spin ground state (S) and uniaxial Ising-like magneto-anisotropy (D). [2] The magnet-like behavior can be observed by slow relaxation of the magnetization below the blocking temperature. Since the discovery of SMMs in the early 1990s, this assumption has formed the basis for the understanding of the origin of the anisotropic barrier. However, in recent years the development of novel lanthanide-only SMMs that challenge and defy this theory pose a number of questions: [3] How can slow relaxation of the magnetization be observed in a nonmagnetic state complex? Why are large energy barriers seen for mononuclear lanthanide(III) complexes? To answer such important questions, it is vital to investigate novel SMMs with high magnetoanisotropy for which the influence of the large negative D value could result in higher anisotropic barriers. Clearly lanthanide-based polynuclear systems are an important avenue to explore in the pursuit of SMMs with higher anisotropic barriers, because of the strong spin-orbit coupling commonly observed in 4f systems. [3] However, lanthanide-only SMMs are rare. [3, The majority of reported SMMs have been prepared with transition-metal ions, [2] although the recent application of a mixed transition-metal/ lanthanide strategy also yielded many structurally and magnetically interesting systems. [6] The scarcity of lanthanide-only SMMs results from the difficulty in promoting magnetic interactions between the lanthanide ions. The interactions can, however, be enhanced by overlapping bridging ligand orbitals. In addition, fast quantum tunneling of the magnetization (QTM), which is common for lanthanide systems, generally prevents the isolation of SMMs with high anisotropic energy barriers.
Inorganics, 2021
The reactions between the bis(1,10-phenantro[5,6-b])tetrathiafulvalene triad (L) and the metallo-precursors Yb(hfac)3(H2O)2 (hfac− = 1,1,1,5,5,5-hexafluoroacetylacetonato anion) and Dy(facam)3 (facam− = 3-trifluoro-acetyl-(+)-camphorato anion) lead to the formation of two dinuclear complexes of formula [Yb2(hfac)6(L)]·2(C7H16) ((1)·2(C7H16)) and [Dy2((+)facam)6(L)]·2(C6H14) ((2)·2(C6H14)). The X-ray structures reveal that the L triad bridges two terminal Yb(hfac)3 or Dy(facam)3 units. (1)·2(C7H16) behaved as a near infrared YbIII centered emitter and a field-induced Single-Molecule Magnet (SMM) while (2)·2(C6H14) displayed SMM behavior in both zero- and in-dc field. The magnetization mainly relaxes through a Raman process for both complexes under an optimal applied magnetic field.
A Trinuclear Radical-Bridged Lanthanide Single-Molecule Magnet
Angewandte Chemie (International ed. in English), 2017
Assembly of the triangular, organic radical-bridged complexes Cp*6 Ln3 (μ3 -HAN) (Cp*=pentamethylcyclopentadienyl; Ln=Gd, Tb, Dy; HAN=hexaazatrinaphthylene) proceeds through the reaction of Cp*2 Ln(BPh4 ) with HAN under strongly reducing conditions. Significantly, magnetic susceptibility measurements of these complexes support effective magnetic coupling of all three Ln(III) centers through the HAN(3-.) radical ligand. Thorough investigation of the Dy(III) congener through both ac susceptibility and dc magnetic relaxation measurements reveals slow relaxation of the magnetization, with an effective thermal relaxation barrier of Ueff =51 cm(-1) . Magnetic coupling in the Dy(III) complex enables a large remnant magnetization at temperatures up to 3.0 K in the magnetic hysteresis measurements and hysteresis loops that are open at zero-field up to 3.5 K.
Inorganic Chemistry, 2018
Controlling quantum tunneling of magnetization (QTM) is a persistent challenge in lanthanide-based single-molecule magnets. As the exchange interaction is one of the key factors in controlling the QTM, we targeted lanthanide complexes with an increased number of radicals around the lanthanide ion. On the basis of our targeted approach, a family of pseudo-octahedral lanthanide/transition-metal complexes were isolated with the general molecular formula of [M(L •−) 3 ] (M = Gd (1), Dy (2), Er (3), Y (4)) using the redox-active iminopyridyl (L •−) ligand exclusively, which possess the highest ratio of radicals to lanthanide reported for discrete metal complexes. Direct current magnetic susceptibility studies suggest that dominant antiferromagnetic interactions exist between the radical and lanthanide ions in all of the complexes, which is strongly corroborated by magnetic data fitting using a Heisenberg−Dirac−Van Vleck (HDVV) Hamiltonian (−2J Hamiltonian). A good agreement between the fit and the experimental magnetic data obtained using g = 2, J rad-rad = −111.9 cm −1 for 4 and g = 1.99, J rad-rad = −111.9 cm −1 , J Gd-rad = −1.85 cm −1 for 1. Complex 2 shows frequency-dependent slow magnetization relaxation dynamics in the absence of an external magnetic field, while 3 shows field-induced frequency-dependent χ M ′′ signals. An ideal octahedral geometry around the lanthanide ion is predicted to be unsuitable for the design of a single-molecule magnet (SMM); nevertheless, complex 2 exhibits slow relaxation of magnetization with a record high anisotropy barrier for a six-coordinate Dy(III) complex. A rationale for this unusual behavior is detailed and reveals the strength of the synthetic methodology developed.
Mononuclear Dysprosium Alkoxide and Aryloxide Single‐Molecule Magnets
Chemistry – A European Journal, 2021
Recent studies have shown that mononuclear lanthanide (Ln) complexes can be high-performing single-molecule magnets (SMMs). Recently,t here has been an influx of mononuclear Ln alkoxide and aryloxide SMMs,w hich have provided the necessary geometrical controlt oi mprove SMM properties and to allow the intricate relaxation dynamics of Ln SMMs to be studied in detail. Here non-aqueous Ln alkox-ide and aryloxide chemistry applied to the synthesis of lowcoordinate mononuclear Ln SMMs are reviewed. The focus is on mononuclear Dy III alkoxide and aryloxide SMMsw ith coordination numbersu pt oe ight, covering synthesis, solidstate structures and magnetica ttributes. Brief overviews are also provided of mononuclear Tb III ,H o III ,E r III and Yb III alkoxide and aryloxide SMMs.