Butterfly-like Heteronuclear 3d–4f Metal Clusters: Synthesis, Structures, Magnetic Properties, and Magnetocaloric Effect

Abstract

This study describes the self-assembled synthesis, characterization, and structural features of two new heterometallic Fe 6 Ln clusters, [Fe 6 Ln(μ 3 -OH) 2 (mdea) 6 (N 3 ) 6 (NO 3 )] (Ln = Y (1), Gd (2); mdeaH 2 = N-methyldiethanolamine). The obtained compounds possess a unique crystalline structure with a vertex-sharing butterfly-like Fe 3 LnFe 3 motif and a rare type of 2,3,4M7-1 topology. The compounds show a new prototype structure with a distinctive arrangement of a lanthanide center between the Fe 3 triangles. Magnetic properties of the obtained clusters were investigated in detail. In 1, the best fit through a spin Hamiltonian to the experimental data of both magnetic susceptibility and magnetization curves gave J values ranging from −5.5 to −11.1 cm −1 . In 2, these values vary from −18.0 to −31.5 cm −1 . The cluster 2 also showed a magnetocaloric effect (MCE) with a −ΔS m value of 10.6 J kg −1 K −1 (16.3 J mol −1 K −1 ) at 2.0 K. This effect is superior to that of other metallacrown compounds (with one Gd inside of an antiferromagnetic matrix of iron centers). The obtained compounds bring a new example of heptametallic clusters into a family of heteronuclear iron(III)-lanthanide derivatives with notable structural characteristics and magnetic behavior.

Single-molecule magnet behavior in heterometallic decanuclear [Ln2Fe8] (Ln = Y, Dy, Ho, Tb, Gd) coordination clusters

“…The bond lengths of Fe–O and Fe–N are in the range of 1.887(6)–2.231(9) Å and 1.934(9)–2.184(7) Å, respectively. The Fe–O bond lengths in 1 are comparable to the YFe 6 cluster of Fe–O bond lengths of 1.936(2)–2.243(2) Å 16 and the Fe–N bond distances correspond to the Y 2 Fe 8 cluster of 2.091(5)–2.216(6) Å. 17 The Y–O bond length falls in the range of 2.279(5)–2.493(4) Å and the O–Y–O bond angles vary from 65.99(16)–152.63(18)°, respectively, in agreement with the bond lengths of 2.245 (9)–2.468 (9) Å and bond angles of 66.1 (3)–159.2 (4)° reported for the Y 4 Fe 4 cluster.…”

Synthesis, structures, and magnetic properties of butterfly-shaped hexanuclear [FeIII4LnIII2] single-molecule magnets

“…Although some Ln III -Fe III heterometallic coordination clusters have been reported, only a few exhibit slow magnetization relaxation in the absence of a static field. [35][36][37][38][39][40][41][42][43][44][45] This behavior might be associated with the stray magnetic fields produced by the Fe III spin centres, which apparently increase the probability of relaxation via quantum tunnelling mechanisms (QTM). 37 The suppression of QTM is usually achieved by applying a DC-biased magnetic field during the AC magnetic measurement.…”

Utilization of diamagnetic Zn(II) ion to boost the anisotropic nature of Ln(III) ion in heterodinuclear Zn(II)–Ln(III) single‐molecule magnets

“…In this context, lanthanide ions are advantageous to design and construct building block SMMs as they possess significant magnetic anisotropy, which is the result of a combination of strong spin-orbit coupling and unquenched orbital angular momentum, and may result in weaker crystal field effects when placed in an appropriate ligand field. [26][27][28][29][30] Utilizing this strategy, an enormous number of heterometallic 3d/4f clusters [31][32][33][34][35] and high symmetry with lownuclearity 4f metal complexes [36][37][38][39][40][41] (mostly containing Dy III ions) displaying SMM behavior were designed. Recently, energy barrier (U eff ) up to 2220 K [42] and blocking temperature (T B ) of 80 K [43] are observed for a dysprosium complex.…”