Key Role of Size and Electronic Configuration on the Sign and Strength of the Magnetic Coupling in a Series of Cu2Ln Trimers (Ln = Ce, Gd, Tb, Dy and Er)

Abstract

Abstract:Five new trinuclear complexes with formula [(CuL α´Me ) 2 Ce(NO 3 ) 3 ] (1) and [(CuL α´Me ) 2 Ln(H 2 O)(NO 3 ) 2 ](NO 3 )¨2(CH 3 OH) (Ln = Gd(2), Tb(3), Dy(4) and Er(5)) have been synthesized using the bidentate N 2 O 2 donor metalloligand [CuL α´Me ] (H 2 L α´Me = N,N 1 -bis(α-methylsalicylidene)-1,3-propanediamine) and structurally characterized. In the case of compound 1, the larger ionic radius of Ce(III) leads to a neutral trinuclear complex with an asymmetric CeO 10 tetradecahedron coordination geometry formed by four oxygen atoms from two (CuL α´Me ) units and three bidentate NO 3´l igands. In contrast, the isomorphic complexes 2-5, with smaller Ln(III) ions, give rise to monocationic trinuclear complexes with a non-coordinated nitrate as a counter ion. In these complexes, the Ln(III) ions show a LnO 9 tricapped trigonal prismatic coordination geometry with C 2 symmetry formed by four oxygen atoms from two (CuL α´Me ) units, two bidentate NO 3´l igands and a water molecule. The magnetic properties show the presence of weak antiferromagnetic interactions in 1 and weak ferromagnetic interactions in 2-5. The fit of the magnetic properties of compounds 2-5 to a simple isotropic-exchange symmetric trimer model, including the anisotropy of the Ln(III) ions, shows that in all cases the Cu-Ln magnetic coupling is weak (J Cu-Ln = 1.81, 1.27, 0.88 and 0.31 cm´1 for 2-5, respectively) and linearly decreases as the number of unpaired f electrons of the Ln(III) decreases. The value found in compound 2 nicely fits with the previously established correlation between the dihedral Cu-O-O-Gd angle and the J value.

New Heterotrinuclear CuIILnIIICuII (Ln = Ho, Er) Compounds with the Schiff Base: Syntheses, Structural Characterization, Thermal and Magnetic Properties

“…As shown in Figure 9, this value decreases by lowering the temperature to 8.05 cm 3 Kmol −1 at 1.8 K. The reduction of χ M T at low temperature should mainly arise from the crystal field splitting of Ln III ions and/or combine the contribution of the overall antiferromagnetic interactions among the metal ions. These results are compatible with the empirical investigations of heterometallic Cu II -4f compounds, in which the 4f ions show a spin-orbit coupling [32,[61][62][63].…”

“…The values of magnetization rise quickly at the low magnetic field whereas at the high magnetic field, the increase of magnetization is slow and linear. The magnetization reaches the values 6.5 µ B for 1 and 7.0 µ B for 2, respectively, at 5T; these are far from the theoretical saturated values anticipated for one uncoupled lanthanide(III) ion and two copper(II) ions [32,[61][62][63].…”

Ligand‐Centered Radical Activity by a Zinc‐Schiff‐Base Complex towards Catechol Oxidation

“…Though this Schiff base ligand ( L ) actually behaves as a polydentate ligand but all the donor centres are not employed in the formation of Zn(II) complex. Previously it was seen that this ligand acted as an important backbone for making hetero‐metallic clusters (3d–4f) which led to important magnetic properties ,. In this present case, this particular ligand actually displays selectivity towards Zn(II) ion and for this reason it is observed that methoxy‐O (O3 & O4) and alkoxy‐O (O6) remains unemployed in the structural building,…”

Syntheses, Crystal Structure and Magnetic Properties of an Unprecedented One-Dimensional Coordination Polymer Derived from an {(NiL)2Ln} Node and a Pyrazine Spacer (H2L=N,N′-Bis(salicylidene)-1,3-propanediamine, Ln=Gd, Tb and Dy)

“…[16, 20, 21] However, such complexes with M=Ln III had rarely been obtained. Recently, we reported the first discrete trinuclear complex [(NiL α−Me ) 2 Ce(NO 3 ) 3 ] (H 2 L α−Me = N,N ′‐bis(α‐methylsalicylidene)‐1,3‐propanediamine) in order to investigate the coordinative interaction of the bidentate metalloligand [NiL α−Me ] with f‐block metal ions.…”