Browsing by Author "Li, L"

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    3d transition metal complexes with a julolidine–quinoline based ligand: structures, spectroscopy and optical properties
    (Royal Society of Chemistry, 2015-12-07) Fanna, DJ; Zhang, YJ; Li, L; Karatchevtseva, I; Shepherd, ND; Azim, A; Price, JR; Aldrich-Wright, JR; Reynolds, JK; Li, F
    A Schiff base type ligand with the combination of the julolidine and the quinoline groups has been reported as a potential chemosensor in detecting the cobalt(II) ion among other heavy and transition metal ions in solution. However, no crystal structure of such a ligand with any metal ions has been reported. In this work, its complexation with 3d transition metal ions (Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)) has been investigated with five new complexes being synthesised, and spectroscopically and structurally characterised. [Mn2L2(CH3OH)2(CH3COO)2]•CH3OH (1) {HL (C22H21N3O) = ((E)-9-((quinolin-8-ylimino)methyl)-1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quinolin-8-ol)} shows a dinuclear structure with two Mn : L : acetate (1 : 1 : 1) units bridged by two methanol molecules. [CoL2(NO3)]•CH3OH•H2O (2) and [NiL2]•H2O (3) exhibit mononuclear structures with a Co : L or Ni : L ratio of 1 : 2. [CuL(CH3COO)]•1/3CH3OH (4) demonstrates a mononuclear structure and the Cu ion has a square planar coordination polyhedron with a L ligand and a highly non-symmetrical acetate anion. [Zn2L2(CH3COO)2]•CH3OH (5) has two types of dinuclear units, both with two ZnL units bridged by two acetate anions but in three different bridging coordination modes. Their vibrational modes, absorption and photoluminescence properties have also been investigated. © 2016 The Partner Organisations
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    Keynote: Modelling the quasi-static and high-strain rate deformation behaviour of magnesium alloy AZ31
    (Scientech, 2015-07-14) Proust, G; Li, L; Flores-Johnson, EA; Shen, LM; Muránsky, O
    In hexagonal close-packed (hcp) metals, plastic deformation is accommodated by different slip and twinning systems. Various factors affect the activation of the deformation mechanisms: alloy composition, grain size, temperature of deformation, strain rate and loading direction. The multiplicity of deformation mechanisms that can be activated and the dependence on loading conditions explain the observed asymmetry and anisotropy on the hardening behaviour and texture evolution. It is therefore important to be able to characterise these deformation mechanisms for specific loading conditions to gain a thorough understanding of the mechanical behaviour of hcp materials. Modern microscopy techniques, such as electron backscatter diffraction (EBSD), enable the quantitative analysis of twinning which is an important deformation mechanics for magnesium alloys. These characterisation techniques allow a better understanding of the way materials deform and provide valuable information for predicting their behaviour. For example using such techniques one can determine the different twinning modes that have contributed to deformation but also the volume fraction of material that has twinned. These microscopy techniques have enabled modellers to better understand the contribution of twinning in the hardening behaviour of the materials and to devise schemes to incorporate the effects of twinning on the hardening response or/and texture evolution of hcp materials. In this work we are investigating the deformation behaviour of magnesium alloys AZ31 under quasi-static and high-strain rate loading. The high-strain rate experiments were carried out using a Hopkinson bar and the microstructure of the deformed samples was measured using EBSD. The experimental results were used to calibrate and test the robustness of a strain-dependent visco-plastic self-consistent crystal plasticity model. © 2015 Scientech
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    A large spin-crossover [Fe4L4]8+ tetrahedral cage
    (Royal Society of Chemistry, 2015-05-20) Li, L; Saigo, N; Zhang, YJ; Fanna, DJ; Shepherd, ND; Clegg, JK; Zheng, RK; Hayami, S; Lindoy, LF; Aldrich-Wright, JR; Li, CG; Reynolds, JK; Harman, DG; Li, F
    A large discrete face-capped tetranuclear iron(II) cage, [Fe4L4](BF4)8·n(solvent), was synthesised via metal-ion directed self-assembly. The cage is formed from a rigid tritopic ligand that incorporates chelating imidazole-imine functional groups. The cage displays temperature induced spin-crossover and LIESST effects and is amongst the largest iron(II) tetrahedral cages with such properties reported. The synthesis, structure and magnetic properties of this new metallo-cage are presented. © 2015 The Royal Society of Chemistry
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    Magnetic ordering and spin dynamics in the S = 5/2 staggered triangular lattice antiferromagnet Ba2MnTeO6
    (American Physical Society, 2020-09-09) Li, L; Narayanan, N; Jin, SJ; Yu, J; Liu, ZJ; Sun, HL; Wang, CW; Peterson, VK; Liu, Y; Danilkin, SA; Yao, DX; Yu, DH; Wang, M
    We report studies of the magnetic properties of a staggered stacked triangular lattice Ba2MnTeO6 using magnetic susceptibility, specific heat, neutron powder diffraction, inelastic neutron scattering measurements, and first-principles density functional theory calculations. Neutron diffraction measurements reveal Ba2MnTeO6 to be antiferromagnetically ordered with a propagation vector k=(0.5,0.5,0) and Néel transition temperature of TN≈20 K. The dominant interaction derived from the Curie-Weiss fitting to the inverse DC susceptibility is antiferromagnetic. Modeling of the inelastic neutron scattering data with linear spin wave theory yielded magnetic exchange interactions for the nearest intralayer, nearest interlayer, and next-nearest interlayer J1=0.27(3), meV J2=0.27(3) meV, and J3=−0.05(1) meV, respectively, and a small value of easy-axis anisotropy of Dzz=−0.01 meV. We derive a magnetic phase diagram that reveals a collinear stripe-type antiferromagnetic order that is stabilized by the competition between J1, J2, and J3. ©2020 American Physical Society
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    Neutron scattering studies on ionic diffusion behaviors of superionic α-Cu2−δ Se
    (AIP Publishing, 2022-10-10) Li, L; Liu, H; Avdeev, M; Yu, DH; Danilkin, SA; Wang, M
    We present studies on crystal structure and ionic diffusion behaviors of superionic Cu2−δ Se (δ = 0, 0.04, and 0.2) by utilizing neutron powder diffraction and quasi-elastic neutron scattering. In the superionic phase, the structural model with Cu ions occupying the Wyckoff sites of 8c and 32f provides the best description of the structure. As the content of Cu increasing in Cu2−δ Se, the Cu occupancy increases on the 32f site but decreases on the 8c site. Fitting to the quasi-elastic neutron scattering spectra reveals two diffusion modes: the localized diffusion between the 8c and 32f sites and the long-range diffusion between the adjacent 8c sites using the 32f site as a bypass. Between 430 and 650 K, we measured that the compound with more Cu content exhibits a larger long-range diffusion coefficient. Temperature in this range does not affect the long-range diffusion process obviously. Our results suggest the two diffusion modes cooperative and, thus, provide a microscopic understanding of the ionic diffusion of the Cu ions in superionic Cu2−δ Se. © 2024 AIP Publishing LLC
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    Self-assembly of a unique 3d/4f heterometallic square prismatic box-like coordination cage
    (Royal Society of Chemistry, 2016-05-23) Li, L; Zhang, Y; Avdeev, M; Lindoy, LF; Harman, DG; Zheng, RK; Cheng, Z; Aldrich-Wright, JR; Li, F
    AbstractWe present the synthesis and characterization of a unique, slightly distorted square prismatic, box-like coordination cage of type [Cu6Dy8L8(MeOH)8(H2O)6](NO3)12·χsolvent obtained via the supramolecular assembly between a non-centrosymmetric Dy(III) metalloligand and Cu(II) nitrate. Magnetic susceptibility measurements indicate that the complex behaves as a single-molecule magnet. © 2016 Royal Society of Chemistry
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    Synthesis and characterisation of two new tripodal metalloligands incorporating zinc(II)
    (Springer Nature, 2015-05-06) Fanna, DJ; Smith, A; Zhang, Y; Li, L; Shepherd, ND; Harman, DG; Li, F
    The in situ Schiff base condensation of 2-acetylpyrazine with tris(2-aminoethyl)amine in the presence of zinc(II) perchlorate was carried out in absolute ethanol and 95 % ethanol, respectively. Two new tripodal metalloligands, 1 and 2, were isolated. The formation of complexes 1 and 2 has been verified by NMR, mass spectral studies and X-ray (for 2), with the evidence indicating that a zinc ion is incorporated in the tripodal cavity defined by the tren backbone in each case. However the products differed in the number of Schiff base condensation reactions that had occurred. While the use of absolute ethanol resulted in condensation at all three primary amine sites of tris(2-aminoethyl)amine, employing 95 % ethanol yielded condensation at only one of the primary amine sites. These different outcomes can be ascribed, at least in part, to the effect of the different water contents in the respective reaction solvents resulting in a shift of the dynamic equilibrium involving imine formation towards the precursor amine and ketone reagents. In 1, steric considerations dictate that the three uncoordinated pyrazine nitrogen donors will have their coordination vectors oriented in a mutually divergent manner suitable for coordination to three different metal centres when acting as a metalloligand while for 2, the X-ray structure confirms that the single uncoordinated (pendent) pyrazine nitrogen is also oriented for ready coordination to a second metal centre. © 2015 Springer Science+Business Media Dordrecht