Linear {Ni II –Ln III –Ni II } Complexes Containing Twisted Planar Ni(μ‐phenolate) 2 Ln Fragments: Synthesis, Structure, and Magnetothermal Properties

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 ] ⋅ 3 NO 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.