Di‐Iron(II) [2+2] Helicates of Bis‐(Dipyrazolylpyridine) Ligands:The Influence of the Ligand Linker Group on Spin State Properties

Kulmaczewski, Rafal and Armstrong, Isaac T. and Catchpole, Pip and Ratcliffe, Emily S. J. and Vasili, Hari Babu and Warriner, Stuart L. and Cespedes, Oscar and Halcrow, Malcolm A. (2022) Di‐Iron(II) [2+2] Helicates of Bis‐(Dipyrazolylpyridine) Ligands:The Influence of the Ligand Linker Group on Spin State Properties. Chemistry - A European Journal. ISSN 0947-6539

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Abstract

Four bis[2‐{pyrazol‐1‐yl}‐6‐{pyrazol‐3‐yl}pyridine] ligands have been synthesized, with butane‐1,4‐diyl (L1), pyrid‐2,6‐diyl (L2), benzene‐1,2‐dimethylenyl (L3) and propane‐1,3‐diyl (L4) linkers between the tridentate metal‐binding domains. L1 and L2 form [Fe2(μ−L)2]X4 (X−=BF4− or ClO4−) helicate complexes when treated with the appropriate iron(II) precursor. Solvate crystals of [Fe2(μ−L1)2][BF4]4 exhibit three different helicate conformations, which differ in the torsions of their butanediyl linker groups. The solvates exhibit gradual thermal spin‐crossover, with examples of stepwise switching and partial spin‐crossover to a low‐temperature mixed‐spin form. Salts of [Fe2(μ−L2)2]4+ are high‐spin, which reflects their highly twisted iron coordination geometry. The composition and dynamics of assembly structures formed by iron(II) with L1−L3 vary with the ligand linker group, by mass spectrometry and 1H NMR spectroscopy. Gas‐phase DFT calculations imply the butanediyl linker conformation in [Fe2(μ−L1)2]4+ influences its spin state properties, but show anomalies attributed to intramolecular electrostatic repulsion between the iron atoms.

Item Type:
Journal Article
Journal or Publication Title:
Chemistry - A European Journal
Uncontrolled Keywords:
/dk/atira/pure/subjectarea/asjc/1600
Subjects:
ID Code:
183322
Deposited By:
Deposited On:
05 Jan 2023 10:00
Refereed?:
Yes
Published?:
Published
Last Modified:
05 Jan 2023 10:00