화학공학소재연구정보센터
Inorganic Chemistry, Vol.55, No.20, 10238-10247, 2016
Synthesis and Magnetic Characterization of Fe(III)-Based 9-Metallacrown-3 Complexes Which Exhibit Magnetorefrigerant Properties
The structural characterization and magnetic properties of three related 9-metallacrown-3 (9-MC-3) structures are reported. Each of these iron complexes is shown to exhibit significant magnetic refrigerant properties. Fe-III(acetate)(3)[9-MCFeN(shi)III-3](MeOH)(3)center dot MeOH center dot 7H(2)O (1-OAc) and Fe-III(benzoate)(3)[9-MCFeN(shi)III-3](MeOH)(3)center dot MeOH center dot 4H(2)O (1-OBz) are structurally analogous tetranuclear iron(III) clusters which exhibit drastically different magnetic properties, due to differences in intermolecular and intramolecular pi interactions which affect superexchange. 1-OAc displays a magnetocaloric effect with a maximum entropy change of -Delta S-m = 15.4 J kg(-1) K-1 at T = 3 K and an applied field change of mu(o)Delta H = 7 T, whereas 1-OBz exhibits a maximum -Delta S-m = 7.4 J kg(-1) K-1 at T = 7 K and mu(o)Delta H = 7 T and displays an inverse magnetocaloric effect at lower temperatures and field changes. 1-OAc has -Delta S-m values comparable to those of other Fe-based MCE materials and displays a significant MCE at lower applied fields, with -Delta S-m = 11.2 J kg(-1) K-1 at 3 K and mu(o)Delta H = 3 T. The tetranuclear core of 1 may be linked with isophthalate to form an octanuclear Fe-2(III)(isophthalate)3[9-MCFeN(shi)III-3](2) dimer (2) that crystallizes in a honeycomb packing arrangement and exhibits solvation-dependent magnetic properties. The MCE for this molecule ranges from -Delta S-m = 9.9 J kg(-1) K-1 at T = 5 K and mu o Delta H = 7 T, when the pores of the material are highly occupied with solvent, to -Delta S-m = 5.4 J kg(-1) K-1, when the system is fully desolvated.