A cyano-bridged FeIIReIV(CN)2 cluster incorporating two high-magnetic anisotropy building units

The pentagonal bipyramidal high-spin iron(II) complex, [(TPA2C(O)NHtBu)Fe(CF3SO3)]+, is shown to exhibit a high-anisotropy ground state, with fits to dc magnetization data providing an axial zero-field splitting parameter of D = − 7.9 cm−1. The utility of this compound as a building unit is demonstrated, as its reaction with [ReCl4(CN)2]2− affords the cyano-bridged dinuclear cluster (TPA2C(O)NHtBu)FeReCl4(CN)2. dc magnetic susceptibility measurements reveal intracluster ferromagnetic exchange interactions between FeII and ReIV centers, with J = +3.0 cm−1, giving rise to a spin ground state of S = 7/2. Moreover, fits to dc magnetization data obtained for the FeRe cluster show the presence of strong axial anisotropy, with D = −2.3 cm−1. Finally, variable-frequency ac susceptibility measurements reveal the onset of slow magnetic relaxation at low temperature, suggesting that the FeRe cluster is a single-molecule magnet.

The pentagonal bipyramidal high-spin iron(II) complex, [(TPA2C(O)NHtBu)FeII(CF3SO3)]+, which exhibits strong uniaxial magnetic anisotropy, reacts with [ReCl4(CN)2]2− to generate the cyano-bridged dinuclear coordination cluster (TPA2C(O)NHtBu)FeReCl4(CN)2. Ferromagnetic exchange coupling between FeII and ReIV ions within the cluster leads to an overall spin ground state of S = 7/2. Uniaxial zero-field splitting of the spin ground state, induced by the single-ion anisotropy of the constituent metal centers, leads to slow magnetic relaxation in the cluster at low temperature.Figure optionsDownload as PowerPoint slideResearch highlights
► The complex [(TPA2C(O)NHtBu)FeII(CF3SO3)]+ exhibits strong uniaxial anisotropy.
► The Fe complex reacts with [ReCl4(CN)2]2− to form an FeRe cluster.
► Ferromagnetic coupling in the FeRe cluster gives rise to an S = 7/2 ground state.
► The FeRe cluster exhibits uniaxial anisotropy and slow magnetic relaxation.