Wells–Dawson
Cages as Molecular Refrigerants
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Abstract
Five clusters with the general formula
[Ni<sub>6</sub>Gd<sub>6</sub>(μ<sub>3</sub>-OH)<sub>2</sub>(μ<sub>2</sub>-OAc)<sub>2</sub>(O<sub>3</sub>PR)<sub>6</sub>(O<sub>2</sub>C<sup><i>t</i></sup>Bu)<sub>16</sub>], where R = methyl
(<b>1</b>), phenyl
(<b>2</b>), <i>n</i>-hexyl (<b>3</b>), benzyl
(<b>4</b>), <i>n</i>-octyl (<b>5</b>), have
been prepared. All of the clusters have a {Ni<sub>6</sub>Gd<sub>6</sub>P<sub>6</sub>} core that can be related to the Wells–Dawson
ion. We have also prepared analogues where the gadolinium is replaced
with diamagnetic yttrium: [Ni<sub>6</sub>Y<sub>6</sub>(μ<sub>3</sub>-OH)<sub>2</sub>(μ<sub>2</sub>-OAc)<sub>2</sub>(O<sub>3</sub>PR)<sub>6</sub>(O<sub>2</sub>C<sup><i>t</i></sup>Bu)<sub>16</sub>] (R = methyl (<b>6</b>), <i>n</i>-hexyl (<b>7</b>), benzyl (<b>8</b>), <i>n</i>-octyl (<b>9</b>)), allowing the magnetic exchange within the
{Ni<sub>3</sub>} units to be analyzed by modeling as the sum of two
noninteracting isosceles triangles. The variation in the magnetic
entropy changes for magnetization (−Δ<i>S</i><sub>M</sub>) among compounds <b>1</b>–<b>5</b> could be attributed not only to the molecular weight of the compounds
but also to intramolecular magnetic interactions
