Synthesis, crystal structures and magnetic behavior of NiII–4f–NiII compounds

We report here synthesis, crystal and molecular structures as well as magnetic measurement results for new heterotrinuclear Schiff base complexes having a general formula [Ni2Ln(L)2(CH3COO)2(MeOH)2]NO3·4H2O (where Ln = LaIII (1) and NdIII (2) and L = C19H18N2O4Br2 = N,N′-bis(5-bromo-3-methoxysalicylidene)-1,3-diaminopropanato) and the mononuclear [NiL(H2O)2] (3) complex. The NiII/4f compounds are isostructural and crystallize in the monoclinic space group P21/n. The lanthanide(III) ion lies on the center of symmetry and is ten-coordinated forming pentagonal antiprism. Compound 3 crystallizes in orthorhombic space group Pnma with the molecule lying on the mirror plane. The complex 1 indicated a weak antiferromagnetic interaction between the terminal NiII ions. The magnetic properties of 2 revealed that the NiII–NdIII interaction is antiferromagnetic. The magnetic data for 3 show dominant zero-field splitting effect of NiII ions.

Graphical abstractThe reaction of Schiff base (N,N′-bis(5-bromo-3-methoxysalicylidene)propylene-1,3-diamine, H2L = C19H20N2O4Br2) with NiII and LnIII ions gave heterotrinuclear compounds formulated as [Ni2Ln(L)2(CH3COO)2(MeOH)2]NO3·4H2O (where Ln = LaIII (1) and NdIII (2)). The complexes are isostructural and crystallize in the monoclinic space group P21/n. The magnetic studies of 1 show the weak antiferromagnetic exchange coupling between terminal NiII ions through the diamagnetic LaIII center. The temperature dependence of the magnetic susceptibility and the field-dependent magnetization indicated that in 2 the interaction between NiII and NdIII ions is antiferromagnetic. The mononuclear [NiL(H2O)2] (3) complex crystallizes in orthorhombic space group Pnma. The magnetic data for 3 show dominant zero-field splitting effect of NiII ions.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Heterotrinuclear NiIILaIIINiII and NiIINdIIINiII compounds. ► Geometry of trinuclear 3d–4f–3d complexes. ► Antiferromagnetic interaction between NiII and NdIII ions.