Browsing by Author "Phonsri, W"

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    Magnetic properties and neutron spectroscopy of lanthanoid-{tetrabromocatecholate/18-crown-6} single-molecule magnets
    (CSIRO Publishing, 2022-03-14) Dunstan, MA; Cagnes, MP; Phonsri, W; Murray, KS; Mole, RA; Boskovic, C
    Lanthanoid single-molecule magnets (Ln-SMMs) exhibit slow magnetic relaxation at low temperatures. This arises from an energy barrier to magnetisation reversal associated with the crystal field (CF) splitting of the Ln(III) ion. The magnetic relaxation is impacted by the interaction of the molecule with the crystal lattice, so factors including particle size and crystal packing can play an important role. In this work, a family of compounds of general formula [Ln(18-c-6)(NO3)(Br4Cat)]·X (Ln = La, Tb, Dy; 18-c-6 = 18-crown-6; Br4Cat2− = tetrabromocatecholate) has been studied by inelastic neutron scattering (INS) and magnetometry to elucidate the effects of crystal packing on the slow magnetic relaxation of the Tb(III) and Dy(III) compounds. The deuterated analogues [Ln(18-c-6-d24)(NO3)(Br4Cat)]·CH3CN-d3 (1-LnD; Ln = La, Tb, Dy) have been synthesised, with 1-TbD and the diamagnetic analogue 1-LaD measured by INS. The dynamic magnetic properties of 1-TbD and 1-DyD have also been measured and compared for two samples with different particle sizes. To probe packing effects on the slow magnetic relaxation, two new solvatomorphs of the hydrogenous compounds [Ln(18-c-6)(NO3)(Br4Cat)]·X (2-Ln: X = CH2Cl2; 3-Ln: X = 0.5 toluene) have been obtained for Ln = Tb and Dy. The CF splitting between the ground and first excited CF pseudo-doublets has been experimentally determined for 1-TbD by INS, and strongly rare earth dependent and anharmonic lattice vibrational modes have also been observed in the INS spectra, with implications for slow magnetic relaxation. Dynamic magnetic measurements reveal significant particle-size dependence for the slow magnetic relaxation for 1-TbD, while a previously reported anomalous phonon bottleneck effect in the 1-DyD analogue does not change with particle size. Further dynamic magnetic measurements of 2-Ln and 3-Ln show that the slow magnetic relaxation in these Ln-SMMs is strongly dependent on lattice effects and crystal packing, which has implications for the future use of Ln-SMMs in devices. © 2022 The Author(s) (or their employer(s)). Published by CSIRO Publishing.
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    Square grid metal–chloranilate networks as robust host systems for guest sorption
    (John Wiley & Sons, Inc, 2019-02-02) Kingsbury, CJ; Abrahams, BF; Auckett, JE; Chevreau, H; Dharma, AD; Duyker, SG; He, QL; Hua, C; Hudson, TA; Murray, KS; Phonsri, W; Peterson, VK; Robson, R; White, KF
    Reaction of the chloranilate dianion with Y(NO3)3 in the presence of Et4N+ in the appropriate proportions results in the formation of (Et4N)[Y(can)2], which consists of anionic square-grid coordination polymer sheets with interleaved layers of counter-cations. These counter-cations, which serve as squat pillars between [Y(can)2] sheets, lead to alignment of the square grid sheets and the subsequent generation of square channels running perpendicular to the sheets. The crystals are found to be porous and retain crystallinity following cycles of adsorption and desorption. This compound exhibits a high affinity for volatile guest molecules, which could be identified within the framework by crystallographic methods. In situ neutron powder diffraction indicates a size-shape complementarity leading to a strong interaction between host and guest for CO2 and CH4. Single-crystal X-ray diffraction experiments indicate significant interactions between the host framework and discrete I2 or Br2 molecules. A series of isostructural compounds (cat)[MIII(X-an)2] with M=Sc, Gd, Tb, Dy, Ho, Er, Yb, Lu, Bi or In, cat=Et4N, Me4N and X-an=chloranilate, bromanilate or cyanochloranilate bridging ligands have been generated. The magnetic properties of representative examples (Et4N)[Gd(can)2] and (Et4N)[Dy(can)2] are reported with normal DC susceptibility but unusual AC susceptibility data noted for (Et4N)[Gd(can)2]. © 2019 Wiley-VCH Verlag GmbH & Co
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    Tetraoxolene-bridged rare-earth complexes: a radical-bridged dinuclear Dy single-molecule magnet
    (Royal Society of Chemistry, 2019-08-22) Reed, WR; Dunstan, MA; Gable, RW; Phonsri, W; Murray, KS; Mole, RA; Boskovic, C
    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.