Synthesis, crystal structures and magnetic properties of two heterometallic {Ln8Cr4} (Ln = Gd³⁺ and Tb³⁺) complexes with one-dimensional wave chain structure

Abstract

Two heterometallic cluster {Ln8Cr4} were constructed from two classical “drum-like” {Ln4Cr2} building units associated by organic ligands HIN, displaying 1D wave chain structure. The MCE values for {Gd8Cr4} at 3 K and 7 T is 23.40 J kg−1 K−1.

Two SiO44–-Templated Ln23Ni20 Clusters with Magnetic Cooling and Stability

“…The magnetization ( M ) and magnetic field ( H ) for compound Gd 23 Ni 20 was studied at T = 1.8–10 K and H = 0–7 T (Figure S21). As H increased, the M increased by degrees and attained the saturation values of 169.00 N μ B at 7.0 T. The experimental values of M were smaller than the theoretical result (201.00 N μ B ) due to the antiferromagnetic exchanges of the metal ions. , …”

“…As H increased, the M increased by degrees and attained the saturation values of 169.00 Nμ B at 7.0 T. The experimental values of M were smaller than the theoretical result (201.00 Nμ B ) due to the antiferromagnetic exchanges of the metal ions. 22,27 The MCE studies of Gd 23 Ni 20 were executed based on the field (0.5−7.0 T) and the temperature (2.0−9.0 K) according to the Maxwell relation for ΔS m (T) = ∫ [∂M (T, H)/ ∂T] H dH. 43 As exhibited in Figure 7, the maximum value of −ΔS m for Gd 23 Ni 20 was 38.15 J kg −1 K −1 at 2.0 K for ΔH = 7.0 T, which was less than the theoretical result of 55.93 J kg −1 K −1 , which was judged by −ΔS m = n Ni Rln (2S Ni + 1)/M r + n Ln Rln (2S Ln + 1)/M r .…”

“…Persistent investigation on the synthetic methods demonstrates suitable ligand and anionic templates are the significant conditions to obtain giant 3d-4f nanoclusters. − With regard to the ligand-controlled hydrolytic method, according to hard–soft acid–base theory, 3d metal ions are inclined to coordinate with soft atoms (such as S and N), while the 4f metal ions tend to bond with hard atoms (such as O and F). , At the same time, the organic ligands containing hard and soft atoms are beneficial to establish giant 3d-4f clusters. For instance, iminodiacetic acid (H 2 IDA) with [N, O, O] donor sites has been widely utilized to construct an extremely diverse family of 3d-4f metal clusters. , Herein, the organic ligand H 2 DTA with multifunctional coordination sites [S, O, O] and a similar structure with H 2 IDA (as depicted in Figure ) is expected to assemble novel high-nuclearity 3d-4f clusters.…”

Magnetic materials based on heterometallic CrII/III–LnIII complexes

“…Antiferromagnetic interaction is dominant between the Ln III ion and Cr III ion. Also, the entropy change for 78a was found to be −Δ S max m = 23.40 J kg −1 K −1 at 3 K and Δ H = 7 T. 138…”

“…71,100,102 Recently, Zhao and group have displayed a significant magnetocaloric effect in a ferromagnetic {Cr III 2 Gd III 3 } cluster having large magnetic entropy change of 27.0 J kg −1 K −1 at 4.0 K. 104 Zhai and group have synthesized a 3-dimensional sulphate framework-based unit having a large MCE of −Δ S max m = 38.33 J kg −1 K −1 at 2 K. 136 Shao and group have employed a building block strategy to generate a neutrally layered 2-dimensional metal coordination polymer consisting of an octanuclear {Cr III 4 Gd III 4 } metal cluster core and an organic ligand as a linker. The complex exhibits a large magnetic entropy of 28.8 J kg −1 K −1 at 3.5 K. 137 Xu and group have constructed a {Ln III 8 Cr III 4 } motif with a one-dimensional chain structure displaying a magnetic entropy change of −Δ S max m = 23.40 J kg −1 K −1 at 3 K. 138 Wen and group have reported the first example of an isolated 3D two-fold interpenetrating Cr III –Gd III framework using a carboxylate ligand having a large magnetocaloric effect of 39.86 J kg −1 K −1 at T = 2 K. 135 There are substantially fewer polynuclear Cr III –Ln III compounds with giant MCE, such as {Cr 4 Ln}, 73 {Cr 6 Ln 2 }, 139 {Cr 2 Ln 4 }, 140 {Cr 4 Ln 4 }, 141 {Cr 3 Ln 7 }, 142 {Cr 12 Ln 4 }, 139 {Cr 2 Ln 5 }, 140 {Cr 4 Ln 8 }. 140 Thus, Cr III –Ln III compounds could be a potential candidate for magnetic refrigerants with large magnetic entropy change; however, Cr III –Ln III compounds are rarely investigated, and thorough and detailed study is needed to establish their fruitfulness as magnetic coolers.…”