1. Modulating Magnetic Refrigeration through Structural Variation in Co II/III -Gd III Clusters.
- Author
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Sheikh JA and Clearfield A
- Abstract
Three heterometallic aggregates, [(Co
II )2 (GdIII )2 (t BuPO3 )2 (O2 Ct Bu)2 (HO2 Ct Bu)2 (NO3 )4 ]·NEt3 (1), [(CoII )2 (CoIII )2 (GdIII )3 (μ3 -OH)2 (t BuPO3 )2 (O2 Ct Bu)9 (deaH)2 (H2 O)2 ] (2), and (CoIII )2 (GdIII )5 (μ2 -OH)(μ3 -OH)2 (t BuPO3 )2 (O2 Ct Bu)10 (HO2 Ct Bu)(deaH)2 ]·MeOH (3), were successfully isolated in reactions of [Co2 (μ-OH2 )(O2 Ct Bu)4 ]·(HO2 Ct Bu)4 , Gd(NO3 )3 ·6H2 O,t Bu-PO3 H2 , 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.- Published
- 2017
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