Enneanuclear [Ni<sub>6</sub>Ln<sub>3</sub>] Cages: [Ln<sup>III</sup><sub>3</sub>] Triangles
Capping [Ni<sup>II</sup><sub>6</sub>] Trigonal Prisms Including a
[Ni<sub>6</sub>Dy<sub>3</sub>] Single-Molecule Magnet
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Abstract
The use of (2-(β-naphthalideneamino)-2-hydroxymethyl-1-propanol)
ligand, H<sub>3</sub>L, in Ni/Ln chemistry has led to the isolation
of three new isostructural [Ni<sup>II</sup><sub>6</sub>Ln<sup>III</sup><sub>3</sub>] metallic cages. More specifically, the reaction of
Ni(ClO<sub>4</sub>)<sub>2</sub>·6H<sub>2</sub>O, the corresponding
lanthanide nitrate salt, and H<sub>3</sub>L in MeCN, under solvothermal
conditions in the presence of NEt<sub>3</sub>, led to the isolation
of three complexes with the formulas [Ni<sub>6</sub>Gd<sub>3</sub>(OH)<sub>6</sub>(HL)<sub>6</sub>(NO<sub>3</sub>)<sub>3</sub>]·5.75MeCN·2Et<sub>2</sub>O·1.5H<sub>2</sub>O (<b>1</b>·5.75MeCN·2Et<sub>2</sub>O·1.5H<sub>2</sub>O), [Ni<sub>6</sub>Dy<sub>3</sub>(OH)<sub>6</sub>(HL)<sub>6</sub>(NO<sub>3</sub>)<sub>3</sub>]·2MeCN·2.7Et<sub>2</sub>O·2.4H<sub>2</sub>O (<b>2</b>·2MeCN·2.7Et<sub>2</sub>O·2.4H<sub>2</sub>O), and [Ni<sub>6</sub>Er<sub>3</sub>(OH)<sub>6</sub>(HL)<sub>6</sub>(NO<sub>3</sub>)<sub>3</sub>]·5.75MeCN·2Et<sub>2</sub>O·1.5H<sub>2</sub>O (<b>3</b>·5.75MeCN·2Et<sub>2</sub>O·1.5H<sub>2</sub>O). The structure of all three clusters
describes a [Ln<sup>III</sup><sub>3</sub>] triangle capping a [Ni<sup>II</sup><sub>6</sub>] trigonal prism. Direct current magnetic susceptibility
studies in the 5–300 K range for complexes <b>1</b>–<b>3</b> reveal the different nature of the magnetic interactions
within the clusters: dominant antiferromagnetic exchange interactions
for the Dy<sup>III</sup> and Er<sup>III</sup> analogues and dominant
ferromagnetic interactions for the Gd<sup>III</sup> example. Alternating
current magnetic susceptibility measurements under zero external dc
field displayed fully formed temperature- and frequency-dependent
out-of-phase peaks for the [Ni<sup>II</sup><sub>6</sub>Dy<sup>III</sup><sub>3</sub>] analogue, establishing its single molecule magnetism
behavior with <i>U</i><sub>eff</sub> = 24 K
