Heterometallic Hexanuclear [Cu₂Ln₄] Complexes Showing Zero‐field SMM Behaviour and Magnetocaloric Effect

Abstract

Three heterometallic hexanuclear 3d–4f complexes bearing the formula [Cu2(L)2Ln4(L)4(o‐van)2] [L=2‐((E)‐((2‐hydroxyphenyl)imino]methyl)phenol; o‐van=ortho‐vanillin] (LnIII=GdIII (1), DyIII (2), and TbIII (3)) have been synthesized and characterized. DC magnetic susceptibility measurements reveal overall antiferromagnetic interactions in 1 and 3, whereas co‐existence of ferro‐ as well as antiferromagnetic interactions were observed in 2. The magnetocaloric effect has been observed for 1 with an entropy change (−ΔSm) of 22.3 J kg−1 K−1 at 3 K and 7 T. Zero‐field single molecule magnet (SMM) behaviour has been observed for 2, where Raman relaxation and quantum tunneling of magnetization (QTM) played a role in magnetization relaxation. The Cu−O−Ln angle well explains the magnetic exchange coupling occurring in the complexes. BS‐DFT calculation for the complexes provides an estimate of the exchange interactions between the paramagnetic centres. Ab initio calculations performed for complex 2 established a good correlation to the experimental relaxation dynamics.

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

“…The deviation between the experimental and theoretical values of −Δ S m is attributed to the existence of antiferromagnetic interactions between Gd (III) ions. [ 74–76 ]…”

“…The deviation between the experimental and theoretical values of ÀΔS m is attributed to the existence of antiferromagnetic interactions between Gd (III) ions. [74][75][76] 3.4 | Thermal stability analysis TGA of all complexes were measured at a rate of 5 C/ min from room temperature to 1000 C under a N 2 atmosphere (Figure S8). Complex 1 exhibits two weight loss processes: The first step loses free acetonitrile, methanol, and water molecules with gradually increasing from room temperature to 108 C, its weight loss is about 4.8% (calcd 5.2%).…”

Synthesis, crystal structure and magnetic properties of octanuclear Ni4Ln4 complexes constructed using a Schiff base ligand and di-2-pyridyl ketone

“…[16][17][18] Up to now, many 3d-Dy complexes with outstanding SMM performance have been reported. [19][20][21][22][23][24][25] Among the 3d metal ions, Ni II might be one of the better candidates for constructing SMMs because it often possesses a large single-ion zero-field splitting. Up to now, many Ni-Dy heterometallic complexes with different nuclearities like NiDy, 26 Ni 2 Dy, 27 Ni 2 Dy 2 , [28][29][30] Ni 3 Dy, 31 Ni 4 Dy 2 , 32 Ni 4 Dy 4 , 33 and Ni 8 Dy 4 , 34 and other high-nuclearity Ni-Dy 35 have been reported.…”

Ferromagnetically coupled CoII2LnIII2 complexes (where LnIII = Ho, Er, Yb): experimental and theoretical investigations

“…[25][26][27] In general the 4f and 3d-4f metal clusters consisting of isotropic metal ions such as Gd III (S = 7/2, 8 S 7/2 ), Mn II , Fe III , Co II , Ni II , and Cu II are widely used to investigate MCE behavior. 12,13,[28][29][30][31][32][33][34][35][36][37][38] Although the high spin and small or negligible magnetic anisotropy are the pre-requisite to achieve magnetothermal properties, a recent report on [{Dy(OAc) 3 (H 2 -O) 2 } 2 ]•4H 2 O (ref. 39) shows that anisotropic metal complexes can also be proposed for MCE properties.…”