Trinuclear heterobimetallic Ni₂Ln complexes [L₂Ni₂Ln][ClO₄] (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er; LH₃ = (S)P[N(Me)NCH-C₆H₃-2-OH-3-OMe]₃): from simple paramagnetic complexes to single-molecule magnet behavior

Abstract

The reaction of LH₃ with Ni(ClO₄)₂·6H₂O and lanthanide salts in a 2:2:1 ratio in the presence of triethylamine leads to the formation of the trinuclear complexes [L₂Ni₂Ln][ClO₄] (Ln = La (2), Ce (3), Pr (4), Nd (5), Sm (6), Eu (7), Gd (8), Tb (9), Dy (10), Ho (11) and Er (12) and L: (S)P[N(Me)N=CH-C₆H₃-2-O-3-OMe]₃). The cationic portion of these complexes consists of three metal ions that are arranged in a linear manner. The two terminal nickel(II) ions are coordinated by imino and phenolate oxygen atoms (3N, 3O), whereas the central lanthanide ion is bound to the phenolate and methoxy oxygen atoms (12O). The Ni-Ni separations in these complexes range from 6.84 to 6.48 Å. The Ni-Ni, Ni-Ln and Ln-O_phenolate bond distances in 2-12 show a gradual reduction proceeding from 2 to 12 in accordance with lanthanide contraction. Whereas all of the compounds (2-12) are paramagnetic systems, 8 displays a remarkable S_T = 11/2 ground state induced by an intramolecular Ni···Gd ferromagnetic interaction, and 10 is a new mixed metal 3d/4f single-molecule magnet generated by the high-spin ground state of the complex and the magnetic anisotropy brought by the dysprosium(III) metal ion.