Cooperative Jahn-Teller Distortion, Phase Transitions, and Weak Ferromagnetism in the KCrF₃ Perovskite

At ambient conditions, the ternary fluoride with formula KCrF3 adopts a perovskite-type structure and incorporates the Jahn-Teller active Cr2+ (d4) whose electronic configuration and magnetic response are analogous to those of Mn3+ (d4) and Cu2+ (d9). These ingredients make it an attractive system to study owing to the striking similarities with LaMnO3 and the expected strong interplay between spin, orbital, and structural ordering phenomena. Indeed, probing the properties of KCrF3 as a function of temperature (5 T 3 exhibits large cooperative Jahn-Teller distortions which are driven by orbital ordering, a series of temperature induced complex structural transitions, and weak ferromagnetism which is reminiscent of what is observed in LaMnO3

Electrochemically Promoted Fluoroalkylation–Distal Functionalization of Unactivated Alkenes

Difunctionalization of olefins represents a powerful synthetic tool and yet a challenging task. This work describes an electrochemically enabled fluoroalkylation–migration reaction of unactivated olefins in the absence of a strong oxidant or heavy metal catalyst, affording fluorinated (hetero)­aryl ketones in good yields and excellent regioselectivities. The efficient and sustainable electrochemical strategy provides a rapid access to a dual functionalized fluorine-containing heterocyclic manifold

[Mn^III₄Ln^III₄] Calix[4]arene Clusters as Enhanced Magnetic Coolers and Molecular Magnets

The use of methylene-bridged calix[4]arenes in 3d/4f chemistry produces a family of clusters of general formula [MnIII4LnIII4(OH)4(C4)4(NO3)2(DMF)6(H2O)6](OH)2 (where C4 = calix[4]arene; Ln = Gd (1), Tb (2), Dy (3)). The molecular structure describes a square of LnIII ions housed within a square of MnIII 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 GdIII ions with the anisotropic TbIII and DyIII 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

Supramolecular Entanglement from Interlocked Molecular Nanomagnets

The trinuclear nanomagnet [MnIII3O(Et-sao)3(MeOH)3](ClO4) (1) has been utilized as a building block for the construction of the hexanuclear cluster [{MnIII3O(Et-sao)3(O2CPh)(EtOH)}2{4,4′-bpe}2] (3) that conforms to a rectangle and the two-dimensional coordination polymer {[MnIII3O(sao)3(4,4′-bpe)1.5]ClO4·3MeOH}n (2·3MeOH). The latter exhibits an unprecedented type of entanglement that is based on host guest interactions. The polygon versus the polymer is rationalized in terms of changing an auxiliary anion that influences the arrangement of the potentially “vacant” coordination axes on each MnIII ion of the trinuclear precursor and thereby directing the self-assembly process

[Mn^III₄Ln^III₄] Calix[4]arene Clusters as Enhanced Magnetic Coolers and Molecular Magnets

The use of methylene-bridged calix[4]arenes in 3d/4f chemistry produces a family of clusters of general formula [MnIII4LnIII4(OH)4(C4)4(NO3)2(DMF)6(H2O)6](OH)2 (where C4 = calix[4]arene; Ln = Gd (1), Tb (2), Dy (3)). The molecular structure describes a square of LnIII ions housed within a square of MnIII 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 GdIII ions with the anisotropic TbIII and DyIII 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

[Mn^III₄Ln^III₄] Calix[4]arene Clusters as Enhanced Magnetic Coolers and Molecular Magnets

The use of methylene-bridged calix[4]arenes in 3d/4f chemistry produces a family of clusters of general formula [MnIII4LnIII4(OH)4(C4)4(NO3)2(DMF)6(H2O)6](OH)2 (where C4 = calix[4]arene; Ln = Gd (1), Tb (2), Dy (3)). The molecular structure describes a square of LnIII ions housed within a square of MnIII 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 GdIII ions with the anisotropic TbIII and DyIII 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