title: Structural and magnetic studies on cyano-bridged rectangular Fe2M2 (M = Cu, Ni) clusters.
abstract: Using the tricyano precursor, (Bu4N)[(Tp)Fe(CN)3] (Tp = Tris(pyrazolyl) hydroborate) (1), four new tetranuclear clusters, [(Tp)Fe(CN)3Cu(Tp)]2.2H2O (2), [(Tp)Fe(CN)3Cu(bpca)]2.4H2O (3) (bpca = bis(2-pyridylcarbonyl)amidate anion), [(Tp)Fe(CN)3Ni(tren)]2(ClO4)2.2H2O (4) (tren = tris(2-amino)ethylamine), and [(Tp)Fe(CN)3Ni(bipy)2]2[(Tp)Fe(CN)3]2.6H2O (5) (bipy = 2,2'-bipyridine), have been synthesized and structurally characterized. The four clusters possess similar square structures, where FeIII and MII (M = CuII or NiII) ions alternate at the rectangle corners. There exist intermolecular - stacking interactions through pyrazolyl groups of Tp- ligands in complexes 2 and 4, which lead to 1D chain structures. Complex 5 shows a 3D network structure through the coexistence of - stacking effects and hydrogen-bonding interactions. Magnetic studies show intramolecular ferromagnetic interactions in all four clusters. The exchange parameters are +11.91 and +1.38 cm(-1) for clusters 2 and 3, respectively, while uniaxial molecular anisotropy can be detected in complex 3 due to the distorted core in its molecular structure. Complex 4 has a ground state of S = 3 and shows SMM behavior with an effective energy barrier of U = 18.9 cm(-1). Unusual spin-glass-like dynamic relaxations are observed for complex 5.
authors.affiliation: Coordination Chemistry Institute and the State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, PR China.
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.forename: Cai-Feng
authors.initials: CF
authors.lastname: Wang
authors.forename: Yi-Zhi
authors.initials: YZ
authors.lastname: Li
authors.forename: Jing-Lin
authors.initials: JL
authors.lastname: Zuo
authors.forename: Xiao-Zeng
authors.initials: XZ
authors.lastname: You