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Spin-crossover complexes in solution, I. Substitutional lability of [Fe(bzimpy)2](ClO4)2

Spin-crossover-Komplexe in Lösung, 1. Mitt.: Substitutionslabilität von [Fe(bzimpy)2](ClO4)2

  • Anorganische Und Physikalische Chemie
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Summary

The iron(II) complexes of the nitrogen donor ligand 2,6-bis(benzimidazol-2′-yl)pyridine (bzimpy) have been investigated in nonaqueous solvents using various spectrophotometric methods. Measurements in methanol at 20°C revealed thatbzimpy can act as a bi-or tridendate ligand towards iron(II) in this solvent, forming [Fe(bzimpy)]2+ (tridendate, logK=5.54), [Fe(bzimpy)2]2+ (bistridentate, logK=4.12) and [Fe(bzimpy)3]2+ (tris-bidentate, logK=3.85). The pronounced thermochromism of the compound is shown to be the result of both spin-crossover and dissociation equilibria. Furthermore, in solvents of higher donor numbers (≥30), partial or complete deprotonation of the complex [Fe(bzimpy)3]2+ is observed. Triethylamine added stepwise to methanolic solutions causes successive deprotonation.

Zusammenfassung

Es wurden Eisen(II) komplexe des Stickstoffdonorliganden 2,6-bis (benzimidazol-2′-yl)pyridin (bzimpy) in nichtwäßrigen Lösungsmitteln mit Hilfe verschiedener spektrophotometrischer Methoden untersucht. Messungen in Methanol bei 20°C zeigten, daßbzimpy gegenüber Eisen(II) sowohl als zwei- als auch als dreizähniger Ligand auftreten kann. Es werden dabei die Verbindungen [Fe(bzimpy)]2+ (tridendat, logK=5.54), [Fe(bzimpy)2]2+ (bis-tridentat, logK=4.12) und [Fe(bzimpy)3]2+ (tris-bidentat, logK=3.85) gebildet. Das ausgeprägte Thermochromieverhalten der Titelverbindung setzt sich aus einem dissoziativen und einem Spin-crossoveranteil zusammen. Weiters wurde in Lösungsmitteln höherer Donorzahl (≥30) eine teilweise oder auch vollständige Deprotonierung des Komplexes [Fe(bzimpy)3]2+ beobachtet. Die schrittweise Zugabe von Triethylamin zu methanolischen Lösungen bewirkt eine fortschreitende Deprotonierung.

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Authors and Affiliations

  1. Institute of Inorganic Chemistry, Technical University of Vienna, A-1060, Vienna, Austria

    Bernhard Strauß, Wolfgang Linert & Viktor Gutmann

  2. Department of Chemistry, The University, DD1 4HN, Dundee, Scotland, UK

    Reginald F. Jameson

Authors
  1. Bernhard Strauß
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  2. Wolfgang Linert
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  3. Viktor Gutmann
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  4. Reginald F. Jameson
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This paper is dedicated to Professor Dr. Wolfgang Beck on the occasion of his 60th birthday with warmest personal wishes

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Strauß, B., Linert, W., Gutmann, V. et al. Spin-crossover complexes in solution, I. Substitutional lability of [Fe(bzimpy)2](ClO4)2 . Monatsh Chem 123, 537–546 (1992). https://doi.org/10.1007/BF00816847

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  • DOI: https://doi.org/10.1007/BF00816847

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