m-Ferrocenylbenzoate-bridged lanthanide coordination polymers: Syntheses, structures, electrochemical and magnetic properties

A series of m-ferrocenylbenzoate [m-ferrocenylbenzoate = m-NaOOCH4C6Fc, Fc = (η5-C5H5)Fe(η5-C5H4)] lanthanide coordination polymers, namely [Ln(μ2-OOCH4C6Fc)(η2-OOCH4C6Fc)(μ2-η2-OOCH4C6Fc)(CH3OH)2]n [Ln = La (1), Pr (2), Nd (3), Sm (4) and Gd (5)], have been synthesized by reactions of m-ferrocenylbenzoate with Ln(NO3)3·nH2O. X-ray crystallographic analyses reveal that 1, 2 and 5 are essentially isostructural with unique one-dimensional linear chain structure. Three types of coordination modes for m-ferrocenylbenzoate are observed in the unit structure which consists of the eight-membered metallacycle Ln2(COO)2 and the rhomboid Ln2O2. Electrochemical studies indicate that 1–5 exhibit a reversible redox wave of FeII/FeIII and the half-wave potentials of 1–5 are slightly more positive than that of m-ferrocenylbenzoic acid. Magnetic investigations show that an antiferromagnetic interaction between Gd(III) ions exists in 5.