Iron lanthanide phosphonate clusters: {Fe6Ln6P 6} Wells-Dawson-like structures with D3d symmetry

Eufemio Moreno Pineda, Floriana Tuna, Yan Zhen Zheng, Simon J. Teat, Richard E P Winpenny, Jürgen Schnack, Eric J L McInnes

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    Abstract

    Reaction of [Fe3(μ3-O)(O2C tBu)6(HO2CtBu)3](O 2CtBu) and [Ln2(O2C tBu)6(HO2CtBu)6] (Ln = lanthanide) with three different phosphonic acids produce a family of highly symmetrical {Fe6Ln6P6} clusters with general formula [Fe6Ln6(μ3-O)2(CO 3)(O3PR)6(O2CtBu) 18], where R = methyl 1, phenyl 2, or n-hexyl 3. All the clusters present an analogous metal frame to the previously reported {Ni 6Ln6P6} both being related to the well-known Wells-Dawson ion from polyoxometallate chemistry. These highly symmetrical clusters have, or approximate very closely to, D3d point symmetry. Both FeIII and GdIII ions are magnetically isotropic and could thus exhibit promising magnetocaloric properties; hence we investigated the {Fe6Gd6P6} compounds accordingly. Modeling the magnetic data of [Fe6Gd6(μ3-O) 2(CO3)(O3PPh)6(O2C tBu)18] by the finite-temperature Lanczos method gave a strong antiferromagnetic Fe···Fe interaction (J Fe-Fe = -30 cm-1) and very weak Gd··· Gd and Gd···Fe exchange interactions (|J| <0.1 cm -1). The strong antiferromagnetic Fe···Fe interaction could account for the relatively smaller -ΔSm value observed, compared against the {Ni6Gd6P6} analogues. © 2014 American Chemical Society.
    Original languageEnglish
    Pages (from-to)3032-3038
    Number of pages6
    JournalInorganic Chemistry: including bioinorganic chemistry
    Volume53
    Issue number6
    DOIs
    Publication statusPublished - 17 Mar 2014

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