Ion-induced diversity in structure and magnetic properties of hexacyanometalate–lanthanide bimetallic assemblies

Abstract

The reaction of trivalent Dy^III/Ho^III, 2,2′:6′,2′′-terpyridine (terpy), and hexacyanometallate [M^III(CN)₆]³⁻ (M = Fe^III and Co^III) leads to the formation of a series of cyano-bridged complexes (1–4). In the case of Dy^III, one-dimensional (1-D) alternating chains [Dy^III(terpy)(DMF)₂(H₂O)₂][M^III(CN)₆]·3H₂O (M = Fe^III for 1 and Co^III for 2) were obtained, where each [M^III(CN)₆]³⁻ entity acts as a bis-monodentate bridging ligand towards two Dy^III ions through two of its six cyanide groups in cis positions, respectively. Contrarily, in the case of Ho^III, a molecular rectangle {[Ho^III(terpy)(DMF)(H₂O)₂][M^III(CN)₆]}₂·nH₂O·2CH₃OH {(M = Fe^III (3) and Co^III (4); and n = 6 or 7} has been formed although the synthesis method is same as for 1 and 2. Interestingly, solid-state direct-current magnetic susceptibility analyses demonstrate competing ferromagnetic interactions for 1 while complex 3 shows antiferromagnetic interactions. The variable-temperature magnetic behaviours observed for 2 and 4 only originate from isolated Dy and Ho ions, since a diamagnetic Co^III metal ion links the magnetic Ln^III ions.