[Mn^III₄Ln^III₄] 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.

Large Magnetocaloric Effect in a Wells–Dawson Type {Ni6Gd6P6} Cage

“…Calculating the entropy changes obtained from the magnetization data ( Figure 3) gives values at 3 K and for a field change DH = 70 kG of: for 1, 26.5; for 2, 12.2; for 3, 5.6 J kg À1 K À1 . The entropy change of 1 is much larger than the value reported for previous 3d-4f compounds at 4 K [5,13] and slightly higher than the highest value reported (25 J kg À1 K À1 ) for a {Mn 14 } cage.…”

Field-induced internal Fe and Ln spin reorientation in butterfly{Fe3LnO2}(LnBadía-Romano1, Bartolomé2, Bartolomé3 et al. 2013Phys. Rev. B222140View full textAdd to dashboardCite

“…[6][7][8][9] The synthesis of molecules combining the magnetic moment and relatively strong exchange interactions of 3d transition metals (M) with the anisotropy naturally provided by lanthanide (Ln) ions is especially promising. Several molecular clusters of this type have been reported, such as {Mn 4 Ln 4 }, 10 {Mn 12 Gd}, 11 and {Cr 4 Dy 4 }, 12 with Ln = heavy Ln's, and {Mn 11 Ln 2 }, 13,14 with Ln = light rare earths. It was found that, in particular, Dy(III) ions are very useful for introducing anisotropy into these molecules, 15 thus confirming the possibility of achieving increased anisotropy in the lanthanide-transition-metal molecular combination.…”

A Trigonal Prismatic Mononuclear Cobalt(II) Complex Showing Single-Molecule Magnet Behavior

“…Since then, they emerged as perspective components for information storage 3 , quantum computing 4 , spintronics 5 , and magnetic refrigeration 6,7 . A necessary condition for a compound to be an SMM is a large axial magnetic anisotropy D that splits the energy levels of a metal ion under zero magnetic field and gives rise to an energy barrier between the states with opposite directions of the magnetic moment U = |D|S 2 (or, for non-integer S, U = |D|(S 2 -1/4)).…”