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High-nuclear heterometallic oxime clusters assembled from triangular subunits: solvothermal syntheses, crystal structures and magnetic properties

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Abstract

Three series of six pyrazine-2-amidoxime (H2pzaox)-based 3d–4f clusters, {Ln8Ni6}, {Ln5Ni10} and {Ln5Ni8} (Ln = Dy and Gd), were solvothermally synthesized in the absence or presence of different coligands, and were structurally and magnetically characterized. The unusual ring-shaped {Ln83-OH)4} core in the two {Ln8Ni6} complexes is generated by four corner-sharing triangle {Ln33-OH)} units, which are further connected to six outer NiII ions by twelve deprotonated H2pzaox ligands in three common binding modes. By contrast, the remaining four clusters contain only two corner-sharing {Ln33-OH)} triangles, which interact with peripheral NiII ions through fourteen H2pzaox ligands in five (for {Ln5Ni10}) and four (for {Ln5Ni8}) different bridging ways. Thus, the interesting core motifs observed in these clusters depend significantly on the number of the triangular {Ln33-OH)} subunits and their connectivity manner with the singly and doubly deprotonated pyrazine-2-amidoxime ligand. Additionally, weak ferromagnetic superexchange in the {Dy5Ni10} and {Ln5Ni8} clusters and antiferromagnetic coupling in {Ln8Ni6} and {Gd5Ni10} clusters was respectively mediated by versatile oximate bridges between the intramolecular LnIII and NiII ions. Furthermore, the three DyIII-derived aggregates exhibit slightly temperature-dependent magnetic relaxations under a zero dc field, and the three GdIII-based clusters display large magnetic entropy changes of 23.5 J kg−1 K−1 for {Gd8Ni6}, 19.4 J kg−1 K−1 for {Gd5Ni10}, and 22.4 J kg−1 K−1 for {Ln5Ni8} at 4.0 K and 70 kOe. These interesting results are helpful for the understanding of oximate-based 3d–4f coordination chemistry and their structure–function relationships.

Graphical abstract: High-nuclear heterometallic oxime clusters assembled from triangular subunits: solvothermal syntheses, crystal structures and magnetic properties

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Publication details

The article was received on 02 Oct 2017, accepted on 20 Nov 2017 and first published on 20 Nov 2017


Article type: Paper
DOI: 10.1039/C7DT03692B
Citation: Dalton Trans., 2018, Advance Article
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    High-nuclear heterometallic oxime clusters assembled from triangular subunits: solvothermal syntheses, crystal structures and magnetic properties

    H. Dong, Z. Zhang, H. Li, Z. Liu, E. Yang and X. Zhao, Dalton Trans., 2018, Advance Article , DOI: 10.1039/C7DT03692B

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