Wells–Dawson Cages as Molecular Refrigerants

Five clusters with the general formula
[Ni6Gd6(μ3-OH)2(μ2-OAc)2(O3PR)6(O2CtBu)16], where R = methyl
(1), phenyl
(2), n-hexyl (3), benzyl
(4), n-octyl (5), have
been prepared. All of the clusters have a {Ni6Gd6P6} core that can be related to the Wells–Dawson
ion. We have also prepared analogues where the gadolinium is replaced
with diamagnetic yttrium: [Ni6Y6(μ3-OH)2(μ2-OAc)2(O3PR)6(O2CtBu)16] (R = methyl (6), n-hexyl (7), benzyl (8), n-octyl (9)), allowing the magnetic exchange within the
{Ni3} units to be analyzed by modeling as the sum of two
noninteracting isosceles triangles. The variation in the magnetic
entropy changes for magnetization (−ΔSM) among compounds 1–5 could be attributed not only to the molecular weight of the compounds
but also to intramolecular magnetic interactions.