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Iron 10-Thiacorroles: Bioinspired Iron(III) Complexes with an Intermediate Spin (S=3/2) Ground State

Authors

  • Dimitri Sakow,

    1. Institut für Anorganische und Analytische Chemie (AAC), Technische Universität Braunschweig, Hagenring 30, 38106 Braunschweig (Germany), Fax: (+49) 531-391-5387
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  • Dr. Dirk Baabe,

    1. Institut für Anorganische und Analytische Chemie (AAC), Technische Universität Braunschweig, Hagenring 30, 38106 Braunschweig (Germany), Fax: (+49) 531-391-5387
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  • Birte Böker,

    1. Institut für Anorganische und Analytische Chemie (AAC), Technische Universität Braunschweig, Hagenring 30, 38106 Braunschweig (Germany), Fax: (+49) 531-391-5387
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  • Dr. Olaf Burghaus,

    1. Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Strasse, 5032 Marburg (Germany)
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  • Dr. Markus Funk,

    1. Institut für Anorganische und Analytische Chemie (AAC), Technische Universität Braunschweig, Hagenring 30, 38106 Braunschweig (Germany), Fax: (+49) 531-391-5387
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  • Dr. Christian Kleeberg,

    1. Institut für Anorganische und Analytische Chemie (AAC), Technische Universität Braunschweig, Hagenring 30, 38106 Braunschweig (Germany), Fax: (+49) 531-391-5387
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  • Dr. Dirk Menzel,

    1. Institut für Physik der Kondensierten Materie (IPKM), Technische Universität Braunschweig, Mendelssohnstrasse 3, 38106 Braunschweig (Germany)
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  • Clemens Pietzonka,

    1. Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Strasse, 5032 Marburg (Germany)
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  • Prof. Dr. Martin Bröring

    Corresponding author
    1. Institut für Anorganische und Analytische Chemie (AAC), Technische Universität Braunschweig, Hagenring 30, 38106 Braunschweig (Germany), Fax: (+49) 531-391-5387
    • Institut für Anorganische und Analytische Chemie (AAC), Technische Universität Braunschweig, Hagenring 30, 38106 Braunschweig (Germany), Fax: (+49) 531-391-5387

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Abstract

A first systematic study upon the preparation and exploration of a series of iron 10-thiacorroles with simple halogenido (F, Cl, Br, I), pseudo-halogenido (N3, I3) and solvent-derived axial ligands (DMSO, pyridine) is reported. The compounds were prepared from the free-base octaethyl-10-thiacorrole by iron insertion and subsequent ligand-exchange reactions. The small N4 cavity of the ring-contracted porphyrinoid results in an intermediate spin (i.s., S=3/2) state as the ground state for the iron(III) ion. In most of the investigated cases, the i.s. state is found unperturbed and independent of temperature, as determined by a combination of X-ray crystallography and magnetometry with 1H NMR-, EPR-, and Mössbauer spectroscopy. Two exceptions were found. The fluorido iron(III) complex is inhomogenous in the solid and contains a thermal i.s. (S=3/2)→high spin (h.s., S=5/2) crossover fraction. On the other side, the cationic bis(pyridine) complex resides in the expected low spin (l.s., S=1/2) state. Chemically, the iron 10-thiacorroles differ from the iron porphyrins mainly by weaker axial ligand binding and by a cathodic shift of the redox potentials. These features make the 10-thiacorroles interesting ligands for future research on biomimetic catalysts and model systems for unusual heme protein active sites.

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