Generalized Heisenberg-Type Magnetic Phenomena in Coordination Polymers with Nickel–Lanthanide Dinuclear Units

Abstract

A new family of 3d–4f coordination polymers with the molecular formula [NiIILnIII(L)­(dca)2(NO3)] n [Ln = Eu (1), Gd (2), Tb (3), Dy (4), and Ho (5); H2L = N,N′-bis­(2-hydroxy-3-methoxy-5-methylbenzyl)­homopiperazine; dca = dicyanamide] has been synthesized in search for new single-molecule magnet (SMM) materials containing highly anisotropic lanthanides. The magnetic properties of these materials have been established by DC and AC magnetometry and explained quantitatively by comprehensive phenomenological modeling based on a generalized Heisenberg-type model, hypothesized previously based on first-principles calculations. Single-crystal X-ray diffraction has shown that the compounds are isostructural, with lanthanide atoms occupying a nine-coordination site with muffin-like geometry and individual NiII–LnIII units linked by dca anions. Other than the paramagnetic compound 1, 2–5 exhibit intra-unit ferromagnetic 3d–4f interactions, favorable for a large spin ground state. A slow field-induced relaxation of magnetization has been observed in compound 4 (only), displaying a substantial energy barrier of U eff/k B = 26.2(5) K, below 6 K. This is attributed to an easy-plane anisotropy and is consistent with the relaxation in systems with a Kramers ground state doublet and hyperfine interactions.

Magnetism Studies of Bis(acyl)phosphide-Supported Eu3+and Eu2+Complexes

“…All air-and moisture-sensitive manipulations were carried out using standard Schlenk techniques or in an MBraun dry box containing a purified argon atmosphere. 1 57 and HgCo(SCN) 4 , 65,66 and the magnetic data were corrected for molecular diamagnetism using Pascal's constants. 67 All samples were ground using an agate mortar and pestle prior to them being loaded into an NMR tube lined with quartz wool and glass filter paper.…”

“…Actual: C = 62.51%, H = 6.44%. 1 Synthesis of Eu( tripp BAP) 3 . EuCl 3 (15 mg, 0.058 mmol) and Na( tripp BAP) (90 mg, 0.17 equiv) were mixed in THF (2 mL) for 2 hr at RT, resulting in a bright orange solution.…”

“…Molecular Eu complexes have continued to gain popularity due to their long-lived luminescence and magnetic properties, making them ideal for numerous applications such as single-molecule magnets and light-emitting diodes. − Many of these complexes are supported by Acac-derived ligands (Acac = acetylacetonate or β-diketonate), with there being over 500 Eu complexes bearing at least three Acac-derived ligands and one neutral supporting ligand in the Cambridge Crystallographic Data Centre (CCDC) . Despite the popularity of Eu 3+ molecular complexes, there have been no reactivity studies of BAP (BAP = bis­(acyl)­phosphide) ligands toward any lanthanide metals.…”

Structures and magnetic properties of two series of Schiff base binuclear lanthanide complexes

“…For complexes 1 and 2, the χ M T values slowly decrease to 23.74 and 22.54 cm 3 K mol À1 at 40 K and then rapidly decline to the minimum of 13.44 and 8.5 cm 3 K mol À1 at 2 K. These behaviors are associated with the presence of Stark energy levels and the magnetic anisotropy of Dy (III), Ho (III). [55][56][57][58] For complex 3, the χ M T value gently declines to 13.05 cm 3 K mol À1 at 12 K, then goes down abruptly to 5.79 cm 3 K mol À1 at 2 K, attributing to intramolecular antiferromagnetic interactions of the Gd (III) ion. [59][60][61][62] The χ M T values for complexes 4-6 (Figure 3b) are 28.03 (4), 26.81 (5) and 15.67 (6) cm 3 K mol À1 at room temperature, which are also slightly lower than the theoretical values for two noninteracting Dy (III) (28.34 cm 3 K mol À1 ), Ho (III) (28.14 cm 3 K mol À1 ), and Gd (III) (15.78 cm 3 K mol À1 ) ions.…”

Two-Dimensional Metal Azides Constructed by a Ln@Co6Cluster and Disordered Co3(N3)11Units

“…In recent years, molecule-based magnetic materials have attracted extensive attention due to their important properties and potential application prospects. − Among them, the 3d–4f heterometallic complexes exhibit various structures and excellent magnetic properties which are significant in both crystal engineering and magnetism investigations. − Many 3d–4f complexes with finite nuclear clusters and infinite structure chains, layers, and networks have been synthesized with different strategies. ,,− In the high-nuclear clusters or coordination polymers, it is found that some 3d–4f clusters have small nuclearity as building blocks, which are connected to each other through the 4f ions. ,− However, the connections that are not conducive to transfer magnetic interactions for 4f electrons are inner shell electrons and are not coupled effectively with other spin carriers . To avoid the above problems, small 3d–4f clusters should be connected by a “magnetic bridge” through the 3d ions.…”