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Issue 5, 2018
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Effect of coordination geometry on the magnetic properties of a series of Ln2 and Ln4 hydroxo clusters

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Abstract

A series of three isostructural tetranuclear complexes with the general molecular formula [Ln43-OH)4(L)42-piv)4(MeOH)4] (Ln = Gd 1, Dy 2 and Ho 3; LH = [1,3-bis(o-methoxyphenyl)-propane-1,3-dione]) were isolated and unambiguously characterized by single crystal XRD. Under similar reaction conditions, simply changing the co-ligand from pivalate to 2,6-bis(hydroxymethyl)-p-cresol (LH′3) led to the isolation of dinuclear Ln(III) complexes with the general molecular formula [Ln2(L)42-LH′2)2]·4DMF (Ln = Gd 4, Dy 5 and Ho 6). Direct current magnetic susceptibility data studies on the polycrystalline sample of 1–6 and the results reveal the existence of weak antiferromagnetic exchange interactions between the lanthanide ions in 1 which is evident from the spin Hamiltonian (SH) parameters (J1 = −0.055 cm−1 and g = 2.01) extracted by fitting χMT(T). On the other hand, though complex 4 exhibits weak antiferromagnetic coupling (J1 = −0.048 cm−1 and g = 1.99) between the Gd(III) ions, the χMT(T) data of complexes 5 and 6 unambiguously disclose the presence of ferromagnetic interactions between Dy(III) and Tb(III) ions at lower temperature. Magnetization relaxation dynamics studies performed on 2 show frequency dependent out-of-phase susceptibility signals in the presence of an optimum external magnetic field of 0.5 kOe. In contrast, complex 5 shows slow magnetization relaxation with an effective energy barrier (Ueff) of 38.17 cm−1 with a pre-exponential factor (τ0) of 1.85 × 10−6 s. The magnetocaloric effect (MCE) of complexes 1 and 4 was extracted from the detailed magnetization measurement and the change in the magnetic entropy (−ΔSm) of 1 and 4 was found to be 25.57 J kg−1 K−1 and 12.93 J kg−1 K−1, respectively, at 3.0 K for ΔH = 70 kOe.

Graphical abstract: Effect of coordination geometry on the magnetic properties of a series of Ln2 and Ln4 hydroxo clusters

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Publication details

The article was received on 16 Jan 2017, accepted on 06 Dec 2017 and first published on 07 Dec 2017


Article type: Paper
DOI: 10.1039/C7DT00172J
Citation: Dalton Trans., 2018,47, 1726-1738
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    Effect of coordination geometry on the magnetic properties of a series of Ln2 and Ln4 hydroxo clusters

    A. Rasamsetty, C. Das, E. C. Sañudo, M. Shanmugam and V. Baskar, Dalton Trans., 2018, 47, 1726
    DOI: 10.1039/C7DT00172J

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