Synthesis of a novel heptacoordinated Fe(iii) dinuclear complex: experimental and theoretical study of the magnetic properties

Gavin A. Craig, Leoní A. Barrios, José Sánchez Costa, Olivier Roubeau, Eliseo Ruiz, Simon J. Teat, Chick C. Wilson, Lynne Thomas, Guillem Aromí

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A new functionalized bis-pyrazol-pyridine ligand has been prepared by reaction with hydrazine of the corresponding bis-β-diketone precursor, also unprecedented. The aerobic reaction of this ligand with ferrous thiocyanate in the presence of ascorbic or oxalic acid affords the dinuclear complex of seven-coordinate Fe(iii), [Fe2(H4L2)2(ox)(NCS)4] (1), as revealed by single crystal X-ray diffraction. This may represent an entry into a new family of [Fe2] compounds with heptacoordinate metal centres. The capacity of this unusual chromophore to undergo magnetic super-exchange was investigated by means of bulk magnetization and DFT calculations. Both approaches confirmed the presence of antiferromagnetic interactions within the molecule. The theoretical investigation has served to describe the magnetic orbitals of Fe(iii) in this unusual coordination geometry, as well as the exchange mechanism. A brief review of the scarce number of iron heptacoordinate complexes reported in the literature is also included and discussed.
Original languageEnglish
Pages (from-to)4874-4881
Number of pages8
JournalDalton Transactions
Issue number20
Early online date26 Mar 2010
Publication statusPublished - 28 May 2010



  • X-ray diffraction
  • aerobic reaction
  • ligand
  • ferrous thiocyanate

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