[CrIII8NiII6]n+ Heterometallic Coordination Cubes

Abstract

Three new heterometallic [Cr^III₈Ni^II₆] coordination cubes of formulae [Cr^III₈Ni^II₆L₂₄(H₂O)₁₂](NO₃)₁₂ (1), [Cr^III₈Ni^II₆L₂₄(MeCN)₇(H₂O)₅](ClO₄)₁₂ (2), and [Cr^III₈Ni^II₆L₂₄Cl₁₂] (3) (where HL = 1-(4-pyridyl)butane-1,3-dione), were synthesised using the paramagnetic metalloligand [Cr^IIIL₃] and the corresponding Ni^II salt. The magnetic skeleton of each capsule describes a face-centred cube in which the eight Cr^III and six Ni^II ions occupy the eight vertices and six faces of the structure, respectively. Direct current magnetic susceptibility measurements on (1) reveal weak ferromagnetic interactions between the Cr^III and Ni^II ions, with J_Cr-Ni = + 0.045 cm^-1. EPR spectra are consistent with weak exchange, being dominated by the zero-field splitting of the Cr^III ions. Excluding wheel-like structures, examples of large heterometallic clusters containing both Cr^III and Ni^II ions are rather rare, and we demonstrate that the use of metalloligands with predictable bonding modes allows for a modular approach to building families of related polymetallic complexes. Compounds (1)-(3) join the previously published, structurally related family of [M^III₈M^II₆] cubes, where M^III = Cr, Fe and M^II = Cu, Co, Mn, Pd.

Keywords: EPR spectroscopy; heterometallic clusters; magnetometry; molecular magnetism; supramolecular chemistry.