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

Abstract

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.