Synthesis, structures and magnetic properties of chiral 3d–3d′–4f heterotrimetallic complexes based on [(Tp*)Fe(CN)3]−

Abstract

A series of 3d–3d′–4f heterotrimetallic compounds originating from (n-Bu₄N)[(Tp*)Fe(CN)₃] (Bu₄N⁺ = tetrabutylammonium cation, Tp* = hydridotris(3,5-dimethylpyrazol-1-yl) borate) and [Cu((R,R)- or (S,S)-3-MeO-salcy)Ln(NO₃)₃(H₂O)] (salcy = N,N′-(1,2-cyclohexanediylethylene)bis(salicylideneiminato) dianion), namely [(Tp*)Fe(CN)₃Cu((R,R)- or (S,S)-3-MeO-salcy)Ln(NO₃)₃(H₂O)₃][(Tp*)Fe(CN)₃]·2MeOH·5H₂O (Ln = Gd for 1-RR and 1-SS, Tb for 2-RR and 2-SS, and Dy for 3-RR and 3-SS), were synthesized. Structural analyses demonstrate that all complexes are made up of a cyanide- and phenolate-bridged heterotrimetallic entity with [(Tp*)Fe(CN)₃Cu((R,R)- or (S,S)-3-MeO-salcy)Ln(NO₃)₃(H₂O)₃] as cation and another [(Tp*)Fe(CN)₃]⁻ unit as anion. Circular dichroism spectra confirm the enantiomeric nature of the optically active complexes. Magnetic studies show that overall ferromagnetic couplings are operative in all complexes. Ac susceptibility measurements under a 1000 Oe dc field demonstrate the Dy and Tb derivatives exhibit frequency-dependent χ′′ signals below 4 K.