An S = 3 cyanide-bridged tetranuclear Fe(III)(2)Ni(II)(2) square that exhibits slow relaxation of magnetization: synthesis, structure and magnetic properties.

The reaction of Ni(II)(dpa)(2)(solvent) (dpa = 2,2'-dipyridyl amine) with [Bu(4)N][(pzTp)Fe(III)(CN)(3)] (Bu(4)N(+) = tetrabutylammonium cation; pzTp = tetrakis(pyrazolyl)borate) in MeOH affords a tetranuclear cyano-bridged cluster, (pzTp)(2)Fe(2)Ni(2)(dpa)(2)(CN)(6)(2).2CH(3)OH.6H(2)O (). Single-crystal X-ray analysis reveals that it is a quasi-square structure with the lateral distance being ca. 5.1 A, 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 show ferromagnetic coupling (J/k = 10.12 K) giving rise to an S = 3 ground state; ac magnetic susceptibility measurements performed on sample showed evidence of the slow relaxation effects possibly associated with single-molecule magnet behavior.