Synthesis, Structure, and Magnetic Properties of an Fe36Dimethylarsinate Cluster: The Largest "ferric Wheel"

Kenneth Hong Kit Lee, Lucas Aebersold, Juan E. Peralta, Khalil A. Abboud, George Christou

Research output: Contribution to journalArticlepeer-review


The synthesis and characterization of a high-nuclearity FeIII/O/arsinate cluster is reported within the salt [Fe36O12(OH)6(O2AsMe2)63(O2CH)3(H2O)6](NO3)12(1). The compound was prepared from the reaction of Fe(NO3)3·9H2O, dimethylarsinic acid (Me2AsO2H), and triethylamine in a 1:2:4 molar ratio in acetonitrile. The Fe36cation of 1 is an unprecedented structural type consisting of nine Fe4butterfly units of two types, three {FeIII43-O)2} units A, and six {FeIII43-O)(μ3-OH)} units B, linked by multiple bridging Me2AsO2-groups into an Fe36triangular wheel/loop with C3crystallographic and D3virtual symmetry that looks like a guitar plectrum. The unusual structure has been rationalized on the basis of the different curvatures of units A and B, the presence of intra-Fe36hydrogen bonding, and the tendency of Me2AsO2-groups to favor μ3-bridging modes. The cations stack into supramolecular nanotubes parallel to the crystallographic c axis and contain badly disordered solvent and NO3-anions. The cation of 1 is the highest-nuclearity "ferric wheel" to date and also the highest-nuclearity Fe/O cluster of any structural type with a single contiguous Fe/O core. Variable-temperature direct-current magnetic susceptibility data and alternating-current in-phase magnetic susceptibility data indicate that the cation of 1 possesses an S = 0 ground state and dominant antiferromagnetic interactions. The Fe2pairwise Ji,jcouplings were estimated by the combined use of a magnetostructural correlation for high-nuclearity FeIII/oxo clusters and density functional theory calculations using broken-symmetry methods and the Green's function approach. The three methods gave satisfyingly similar Ji,jvalues and allowed the identification of spin-frustration effects and the resulting relative spin-vector alignments and thus rationalization of the S = 0 ground state of the cation.

Original languageEnglish
Pages (from-to)17256-17267
Number of pages12
JournalInorganic Chemistry
Issue number43
StatePublished - Oct 31 2022


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