Linear {NiII-LnIII-NiII} complexes containing twisted planar Ni(μ-phenolate)2 Ln fragments: synthesis, structure, and magnetothermal properties.

Abstract

Sequential reaction of a multisite LH(4) ligand {2-[2-hydroxy-3-(hydroxymethyl)-5-methylbenzylideneamino]-2-methylpropane-1,3-diol} with appropriate lanthanide salts followed by the addition of Ni(NO(3))(2)⋅6 H(2)O in a 4:1:2 stoichiometric ratio in the presence of triethylamine afforded four heterobimetallic trinuclear complexes [Ni(2)Gd(LH(3))(4)]⋅3NO(3)⋅3 MeOH⋅H(2)O⋅CH(3)CN (1), [Ni(2)Tb(LH(3))(4)]⋅(3 )NO(3)⋅3 MeOH⋅CH(3)CN (2), [Ni(2)Dy(LH(3))(4)]⋅3 NO(3)⋅3 MeOH⋅H(2)O⋅CH(3)CN (3), and [Ni(2)Ho(LH(3))(4)]⋅3 NO(3)⋅3 MeOH⋅H(2)O⋅CH(3)CN (4). Complexes 1-4 possess linear trimetallic cores with a central lanthanide ion. Magnetic studies revealed a predominant ferromagnetic interaction between the Ni and Ln centers. Alternating current susceptibility measurements of complex 3 showed a small frequency dependence of the out-of-phase signal, χ''(M), under zero direct current field, but without achieving a net maximum above 2 K. Magnetic studies on 1 revealed that it has a significant magnetocaloric effect.