Magnetic Properties of High-Nuclearity Fex-oxo (x = 7, 22, 24) Clusters Analyzed by a Multipronged Experimental, Computational, and Magnetostructural Correlation Approach

Ashlyn R. Hale, Megan E. Lott, Juan E. Peralta, Dolos Foguet-Albiol, Khalil A. Abboud, George Christou

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Abstract

The synthesis, structure, and magnetic properties of three related iron(III)-oxo clusters are reported, [Fe7O3(O2CPh)9(mda)3(H2O)] (1), [Fe22O14(OH)3(O2CMe)21(mda)6](ClO4)2(2), and [Fe24O15(OH)4(OEt)(O2CMe)21(mda)7](ClO4)2(3), where mdaH2is N-methyldiethanolamine. 1 was prepared from the reaction of [Fe3O(O2CPh)6(H2O)3](NO3) with mdaH2in a 1:2 ratio in MeCN, whereas 2 and 3 were prepared from the reaction of FeCl3/NaO2CMe/mdaH2in a 2:â 13:2 ratio and FeCl3/NaO2CMe/mdaH2/pyridine in a 2:â 13:2:25 ratio, respectively, both in EtOH. The core of 1 consists of a central octahedral FeIIIion held within a nonplanar Fe6loop by three μ3-O2-and three μ2-RO-arms from the three mda2-chelates. The cores of the cations of 2 and 3 consist of an A:B:A three-layer topology, in which a central Fe6(2) or Fe8(3) layer B is sandwiched between two Fe8layers A. The A layers structurally resemble 1 with the additional Fe added at the center to retain virtual C3symmetry. The central Fe6layer B of 2 consists of a {Fe44-O)23-OH)2}6+cubane with an Fe on either side attached to cubane O2-ions, whereas that of 3 has the same cubane but with an {Fe33-O)(μ-OH)} unit attached on one side and a single Fe on the other. Variable-Temperature dc and ac magnetic susceptibility studies revealed dominant antiferromagnetic coupling in all complexes leading to ground-state spins of S = 5/2for 1 and S = 0 for 2 and 3. All Fe2pairwise exchange parameters (Jij) for 1-3 were estimated by two independent methods: density functional theory (DFT) calculations using broken symmetry methods and a magnetostructural correlation previously developed for high-nuclearity FeIII/O complexes. The two approaches gave satisfyingly similar Jijvalues, and the latter allowed rationalization of the experimental ground states by identification of the spin frustration effects operative and the resultant relative spin vector alignments at each FeIIIion.

Original languageEnglish
Pages (from-to)11261-11276
Number of pages16
JournalInorganic Chemistry
Volume61
Issue number29
DOIs
StatePublished - Jul 25 2022
Externally publishedYes

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