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Bispidine Platform Grants Full Control over Magnetic State of Ferrous Chelates in Water

Authors

  • Jacek Lukasz Kolanowski,

    1. Laboratoire de Chimie, École Normale Supérieure de Lyon, 46 allée d'Italie, 69364 Lyon (France), Fax: (+33) 472 72 88 60
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  • Dr. Erwann Jeanneau,

    1. Centre de Diffractométrie Henri Longchambon, Université Lyon 1, 5 rue de la Doua, 69100 Villeurbanne (France)
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  • Robert Steinhoff,

    1. Laboratoire de Chimie, École Normale Supérieure de Lyon, 46 allée d'Italie, 69364 Lyon (France), Fax: (+33) 472 72 88 60
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    • M.Sc. intern on leave from the Technical University of Munich.

  • Prof. Dr. Jens Hasserodt

    Corresponding author
    1. Laboratoire de Chimie, École Normale Supérieure de Lyon, 46 allée d'Italie, 69364 Lyon (France), Fax: (+33) 472 72 88 60
    • Laboratoire de Chimie, École Normale Supérieure de Lyon, 46 allée d'Italie, 69364 Lyon (France), Fax: (+33) 472 72 88 60
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Abstract

A bicyclic ligand platform for iron(II), which allows total control over the complex’s magnetic properties in aqueous solution simply by varying one of the six coordination sites of the bispidine ligand, is reported. To achieve this, an efficient synthetic route to an N5 bispidine framework (ligand L4) that features an unsubstituted N-7 site is established. Then, by choosing appropriate N-7-coordinating substituents, the spin state of choice can be imposed on the corresponding ferrous complexes under environmentally relevant conditions in water and near-room temperature. Importantly, the first low-spin and diamagnetic iron(II) chelates in the bispidine series, both in the solid state and in aqueous solution, are reported. The eradication of head-on steric clashes between pendent coordinating arms is at the origin of this success. A new pair of constitutionally similar ferrous coordination compounds of a multidentate ligand system is obtained, which exhibits a distinctly binary (off–on) magnetic relationship. The new synthetic intermediate L4 may be substituted in just one step by any desired pendent arm, thus allowing access to complexes with finely tuned magnetic properties.

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