Trinuclear nickel–lanthanide compounds

Abstract

The Schiff base compound 2,2′-{[(2-aminoethyl)imino]bis[2,1-ethanediyl-nitriloethylidyne]}bis-2-hydroxy-benzoic acid (H₄L) as a proligand was prepared in situ from 3-formylsalicylic acid with tris(2-aminoethyl)amine (tren). The trinuclear 3d–4f metal complexes of this ligand {[Ln{Ni(H₂L)(tren)}₂](NO₃)₃} (Ln = Gd, Dy, Er, Lu) could be obtained as single crystalline material by synthesizing the proligand in the presence of the metal salts [Ni(NO₃)₂·(H₂O)₆] and [Ln(NO₃)₃·(H₂O)_m] (Ln = Gd, Dy, Er, Lu). In the solid state, the complexes adapt a new V shaped structure. Mass spectrometric ion signals related to the trinuclear complexes were detected both in positive and negative ion mode via electrospray ionization mass spectrometry supporting the single crystal X-ray analysis. Hydrogen/deuterium exchange (HDX) experiments in solution support the fragmentation scheme. The magnetic studies on all these compounds suggest the presence of weak antiferromagnetic interactions between neighboring metal centers.