Modulating Magnetic Refrigeration through Structural Variation in CoII/III–GdIII Clusters
dataset
posted on 2017-02-10, 17:48 authored by Javeed Ahmad Sheikh, Abraham ClearfieldThree heterometallic
aggregates, [(CoII)2(GdIII)2(tBuPO3)2(O2CtBu)2(HO2CtBu)2(NO3)4]·NEt3 (1), [(CoII)2(CoIII)2(GdIII)3(μ3-OH)2(tBuPO3)2(O2CtBu)9(deaH)2(H2O)2] (2), and (CoIII)2(GdIII)5(μ2-OH)(μ3-OH)2(tBuPO3)2(O2CtBu)10(HO2CtBu)(deaH)2]·MeOH (3), were successfully isolated in reactions of [Co2(μ-OH2)(O2CtBu)4]·(HO2CtBu)4, Gd(NO3)3·6H2O, tBu-PO3H2, and diethanolamine (deaH3) by varying the stoichiometry
of the reactants and/or changing the solvent. The structures of the
final products were profoundly affected by these minor changes in
stoichiometry or a change in solvent. The metal–oxo core of
these complexes displays a hemicubane or a defective dicubane-like
view. Bond valence sum calculations and bond lengths indicate the
presence of CoII centers in compound 1, mixed
valent Co centers (CoII/CoIII) in compound 2, and only CoIII centers in compound 3 as required for the charge balances and supported by the magnetic
measurements. Magnetic studies reveal significant magnetic entropy
changes for complexes 1–3 (−ΔSm values of 28.14, 25.06, and 29.19 J kg–1 K–1 for 3 K and 7 T, respectively).
This study shows how magnetic refrigeration can be affected by anisotropy,
magnetic interactions (ferro- or antiferromagnetic), the metal/ligand
ratio, and the content of GdIII in the molecule.
