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Magnetic Interaction Affecting the Zero-Field Single-Molecule Magnet Behaviors in Isomorphic {NiII2DyIII2} and {CoII2DyIII2} Tetranuclear Complexes
journal contribution
posted on 2017-09-06, 12:04 authored by Haipeng Wu, Min Li, Sheng Zhang, Hongshan Ke, Yiquan Zhang, Guilin Zhuang, Wenyuan Wang, Qing Wei, Gang Xie, Sanping ChenGreat
interest is being shown in investigating magnetic interactions that
efficiently influence lanthanide single-molecule magnet behavior.
A series of heterometallic complexes [M2Ln2(Hhms)2(CH3COO)6(CH3OH)2(H2O)2]·(NO3)2 (M = NiII, Ln = DyIII (1), GdIII (2), and YIII (3); M = CoII, Ln = DyIII (4), GdIII (5), and YIII (6)) have been prepared with a compartmental Schiff-base
ligand, 1-(2-hydroxy-3-methoxybenzylidene)-semicarbazide (H2hms), featuring a zigzag-shaped MII-LnIII-LnIII-MII metallic core arrangement. In complexes 1–6, a unique monophenoxo/diacetate asymmetric
bridging connects MII ion with LnIII ion, and
four acetates bridge two LnIII ions where acetates play
essential roles as coligand in generating the tetranuclear units.
Magnetic studies reveal the presence of predominant ferromagnetic
coupling in DyIII and GdIII derivatives, and
slow relaxation of magnetization is observed for {Ni2IIDy2III} and {CoII2DyIII2} with an energy barrier of 16.0 K for
{Ni2IIDy2III} and 6.7
K for {CoII2DyIII2} under
zero static field. Compared with the analogue {CoII2DyIII2}, the {Ni2IIDy2III} shows longer relaxation time and an
absence of the quantum tunnelling of the magnetization (QTM) at low
temperatures. Ab initio calculations suggest that
the zero-field QTM of {Ni2IIDy2III} is effectively interrupted thanks to the ferromagnetic
exchange coupling generated between NiII and DyIII ions. The presence of ferromagnetic exchange between NiII and DyIII ions is more conducive to zero-field single-molecule
magnet behaviors than in isomorphic {CoII2DyIII2} where the exchange is antiferromagnetic.
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Dy IIIY IIIZero-Field Single-Molecule Magnet BehaviorsLn III ionOHLn III ionsinfluence lanthanide single-molecule magnet behaviorcompartmental Schiff-base ligandCOOzero-field single-molecule magnet behaviorsNi 2 II Dy 2 IIIQTMCHM II ionAb initio calculationszigzag-shaped M IICo II 2 Dy III 2Dy III ionsTetranuclear Complexes Great interestGd III derivativesLn IIINi II 2 Dy III 2Ni IIM 2 Ln 2Magnetic Interaction Affecting
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