An S = 3 cyanide-bridged tetranuclear FeIII2NiII2 square that exhibits slow relaxation of magnetization: synthesis, structure and magnetic properties

Abstract

The reaction of [Ni^II(dpa)₂(solvent)]²⁺ (dpa = 2,2′-dipyridyl amine) with [Bu₄N][(pzTp)Fe^III(CN)₃] (Bu₄N⁺ = tetrabutylammonium cation; pzTp = tetrakis(pyrazolyl)borate) in MeOH affords a tetranuclear cyano-bridged cluster, [(pzTp)₂Fe₂Ni₂(dpa)₂(CN)₆](ClO₄)₂·2CH₃OH·6H₂O (1). Single-crystal X-ray analysis reveals that it is a quasi-square structure with the lateral distance being ca. 5.1 Å, in which two opposing dpa-ligated Ni^II ions (S = 1) are linked through cyanide bridges to two pzTp-ligated Fe^III (S = 1/2) centers at the corner sites. Magnetic studies for complex 1 show ferromagnetic coupling (J/k = 10.12 K) giving rise to an S = 3 ground state; ac magnetic susceptibility measurements performed on sample 1 showed evidence of the slow relaxation effects possibly associated with single-molecule magnet behavior.