Syntheses, structures and magnetic properties of cyano-bridged one-dimensional Ln³⁺–Fe³⁺ (Ln = La, Dy, Ho and Yb) coordination polymers

Four new heterometallic one-dimensional coordination polymers with formulae trans-[La(o-phen)3(H2O)(μ-CN)2Fe(CN)4]·7H2O (1) and trans-[Ln(H2O)2(phen)2(μ-CN)2Fe(CN)4]·nH2O [Ln/n = Dy/8 (2), Ho/7 (3) and Yb/7 (4), (o-phen = 1,10-phenanthroline)] have been synthesized by reacting Ln(NO3)3·xH2O with K3[Fe(CN)6] and 1,10-phenanthroline. The structures of 1–4 have been established by single crystal X-ray diffraction. Polymer 1 presents a chain structure with three o-phen ligands coordinated to La3+ and [Fe(CN)6]3− complexes connecting them through two trans CN− ligands to form a linear chain. Compounds 2–4 are solvates and contain Ln3+ ions coordinated to two o-phen ligands and also bridged by [Fe(CN)6]3− complexes through two trans CN− ligands. The chains are connected by hydrogen bonds and a cluster of ten water molecules in the structures of 2–4. The temperature dependent magnetic susceptibility of 2–4 reveals that the Ln3+–Fe3+ interaction is weakly antiferromagnetic and the Fe(III) and Ln3+ ions behave as almost isolated centres.