[Mn(III)4Ln(III)4] calix[4]arene clusters as enhanced magnetic coolers and molecular magnets

Georgios Karotsis; Stuart Kennedy; Simon J Teat; Christine M Beavers; Drew A Fowler; Juan J Morales; Marco Evangelisti; Scott J Dalgarno; Euan K Brechin

doi:10.1021/ja104848m

[Mn(III)4Ln(III)4] calix[4]arene clusters as enhanced magnetic coolers and molecular magnets

J Am Chem Soc. 2010 Sep 22;132(37):12983-90. doi: 10.1021/ja104848m.

Authors

Georgios Karotsis¹, Stuart Kennedy, Simon J Teat, Christine M Beavers, Drew A Fowler, Juan J Morales, Marco Evangelisti, Scott J Dalgarno, Euan K Brechin

Affiliation

¹ School of Chemistry, The University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, Scotland, UK.

PMID: 20677762
DOI: 10.1021/ja104848m

Abstract

The use of methylene-bridged calix[4]arenes in 3d/4f chemistry produces a family of clusters of general formula [Mn(III)(4)Ln(III)(4)(OH)(4)(C4)(4)(NO(3))(2)(DMF)(6)(H(2)O)(6)](OH)(2) (where C4 = calix[4]arene; Ln = Gd (1), Tb (2), Dy (3)). The molecular structure describes a square of Ln(III) ions housed within a square of Mn(III) ions. Magnetic studies reveal that 1 has a large number of molecular spin states that are populated even at the lowest investigated temperatures, while the ferromagnetic limit S = 22 is being approached only at the highest applied fields. This, combined with the high magnetic isotropy, makes the complex an excellent magnetic refrigerant for low-temperature applications. Replacement of the isotropic Gd(III) ions with the anisotropic Tb(III) and Dy(III) ions "switches" the magnetic properties of the cluster so that 2 and 3 behave as low-temperature molecular magnets, displaying slow relaxation of the magnetization.