A Novel Undecametallic Iron(III) Cluster with an S = 11/2 Spin Ground State

The reaction of [NEt4]2[Fe2OCl6] with sodium benzoate, 4,6-dimethyl-2-hydroxypyrimidine (dmhp), and 1,1,1-tris(hydroxymethyl)ethane (H3thme) gives the undecametallic compound [NEt4][Fe11O4(O2CPh)10(thme)4(dmhp)2Cl4]. X-ray crystallography, EPR spectroscopy, bulk magnetic susceptibility studies, and low-temperature single-crystal magnetic measurements were used to characterize the compound. Magnetic measurements indicate an S = 11/2 ground state with the parameters g = 2.03 and D = -0.46 cm^-1. Single-crystal magnetic studies show hysteresis of molecular origin at T < 1.2 K with fast quantum mechanical tunneling at zero field.