Magnetic Properties of Cyano-Bridged Ln³⁺−M³⁺ Complexes. Part I: Trinuclear Complexes (Ln³⁺ = La, Ce, Pr, Nd, Sm; M³⁺ = Fe_LS, Co) with bpy as Blocking Ligand

The reaction of Ln(NO3)3(aq) with K3[Fe(CN)6] or K3[Co(CN)6] and 2,2‘-bipyridine in water/ethanol led to eight trinuclear complexes: trans-[M(CN)4(μ-CN)2{Ln(H2O)4(bpy)2}2][M(CN)6]·8H2O (M = Fe3+ or Co3+, Ln = La3+, Ce3+, Pr3+, Nd3+, and Sm3+). The structures for the eight complexes [La2Fe] (1), [Ce2Fe] (2), [Pr2Fe] (3), [Nd2Fe] (4), [Ce2Co] (5), [Pr2Co] (6), [Nd2Co] (7), and [Sm2Co] (8) have been solved; they crystallize in the triclinic space group P1̄ and are isomorphous. They exhibit a supramolecular 3D architecture through hydrogen bonding and π−π stacking interactions. A stereochemical study of the nine-vertex polyhedra of the lanthanide ions, based on continuous shape measures, is presented. No significant magnetic interaction was found between the lanthanide(III) and the iron(III) ions.