title: [Mn(III)4Ln(III)4] calix[4]arene clusters as enhanced magnetic coolers and molecular magnets.
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.
authors.affiliation: School of Chemistry, The University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, Scotland, UK.
authors.forename: Georgios
authors.initials: G
authors.lastname: Karotsis
authors.forename: Stuart
authors.initials: S
authors.lastname: Kennedy
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Teat
authors.forename: Christine M
authors.initials: CM
authors.lastname: Beavers
authors.forename: Drew A
authors.initials: DA
authors.lastname: Fowler
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Morales
authors.forename: Marco
authors.initials: M
authors.lastname: Evangelisti
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Dalgarno
authors.forename: Euan K
authors.initials: EK
authors.lastname: Brechin