New Families of Hetero-tri-spin 2p−3d−4f Complexes: Synthesis, Crystal Structures, and Magnetic Properties

Abstract

In this work we report the synthesis, crystal structures, and magnetic behavior of 2p-3d-4f heterospin systems containing the nitroxide radical 4-azido-2,2,6,6-tetramethylpiperidine-1-oxyl radical (N3tempo). These compounds were synthesized through a one-pot reaction by using [Cu(hfac)2], [Ln(hfac)3] (hfac = hexafluoroacetylacetonate, Ln = Dy(III), Tb(III) or Gd(III)), and the N3tempo radical. Depending on the stoichiometric ratio used, the synthesis leads to penta- or trimetallic compounds, with molecular formulas [Cu3Ln2(hfac)8(OH)4(N3tempo)] (Ln = Gd, Tb, Dy) and [CuLn2(hfac)8(N3tempo)2(H2O)2] (Ln = Gd, Dy). The magnetic properties of all compounds were investigated by direct current (dc) and alternating current (ac) measurements. The ac magnetic susceptibility measurements of Tb(III)- and Dy(III)-containing compounds of both families revealed slow relaxation of the magnetization, with magnetic quantum tunneling in zero field.

Stepwise Investigation of the Influences of Steric Groups versus Counterions To Target Cu/Dy Complexes

“…The structure of 2 is shown in Figure 1, together with its core structure, which helps to illustrate the connection modes between the different metal centers. The core has some similarities to a previously published Cu3Ln2 structure from Vaz et al 53 Figure 1. Molecular structure of Cu3Dy2 (2) (above) and its cluster core (below).…”

“…While Dy(1) exhibits an eight-coordinate environment, Dy(2) has a nine-coordinate ligand sphere, similar to the environments around the Dy III ions in the previously published Cu3Dy2 complex. 53 Dy(1) is very close to a square antiprismatic environment, which can also be easily visualized from Figure 7, while the shape of Dy(2) is much closer to a tricapped trigonal prism, but again the deviation from a muffin shape is quite small, see Figure 7 and Table 4. SHAPE 86 is particularly helpful to estimate the shapes of the coordination polyhedral, especially in the complicated Cu5Dy5 (3) structure with its different ligand environments, but all being surrounded by eight coordinating atoms.…”

“…28 While Cu9Dy2 can be described as 1,2,3,4,6M11-1, the pentanuclear complex 2 is described as 2,3,4M5-2 and the decanuclear complex 3 as 1,2,2,3,4,5,5,6,6M10-1. To the best of our knowledge, 1 and 3 are not related to any structural motif whereas 2 is the second paradigm 53 within the Cu/Dy literature, which is summarized in Table 2. Thus, to the best of our knowledge, whereas 1 forms an extension of the topology previously observed for a Cu5Gd2 copound 28 and 2 has the same topology as the previously described Cu3Dy2, 53 the topology of 3 is completely new, see Table 2.…”

Construction of Nitronyl Nitroxide‐Based 3d–4f Clusters: Structure and Magnetism

“…It is noteworthy that most of the obtained 3d-4f SMMs are based on diamagnetic ligands so far while paramagnetic, radical-bridged 3d-4f SMMs have not been reported with the exception of one example of a tempo radical-based 2p-3d-4f SMM reported very recently. [8] The nitronyl nitroxide radical is an appealing building block to construct molecular magnetic materials with a strong intramolecular magnetic exchange coupling, [9] which is beneficial for single-molecule magnets. Recently, 1D and 2D nitronyl nitroxide-based 3d-4f compounds have been reported; [10] however, a nitronyl nitroxide-bridged 3d-4f cluster has thus far not been reported.…”

Structural and Magnetic Properties of 2p‐3d‐4f Hetero‐Tri‐Spin Chains Comprising [{Cu(hfac)2‐Radical}2] Dimers and Ln(hfac)3 (hfac=hexafluoroacetylacetonate)

“…Hetero‐tri‐spin 2p‐3d‐4f compounds provide an opportunity to design and synthesize new 1D heterospin systems . A series of hetero‐tri‐spin 2p‐3d‐4f chains based on nitroxide radicals have also been reported recently . Very recently, novel hetero‐tri‐spin 2p‐3d‐4f one‐dimensional chains that consist of [{Cu(NIT‐3 Py)} 2 ] rings bridged by Ln(hfac) 3 units were obtained .…”