title: Syntheses, crystal structures and magnetic properties of cyano- and phenoxide-bridged Fe(iii)Mn(iii) tetramers containing fac-Fe(iii) tricyanides and Mn(iii) Schiff bases.
abstract: Three cyanide-linked Fe(iii)Mn(iii) bimetallic clusters, [(Tp)Fe(CN)(3)](2)[Mn(acphen)](2) [; acphen = N,N'-ethylenebis(2-hydroxyacetophenylideneiminato) dianion], [(Tp)Fe(CN)(3)](2)[Mn(5-Bracphen)](2) [; 5-Bracphen = N,N'-ethylenebis(5-bromo-2-hydroxyacetophenylideneiminato) dianion], and [(Tp)Fe(CN)(3)](2)[Mn(salen)](2).6H(2)O [; salen = N,N'-ethylenebis(salicylidineiminato) dianion], were prepared by self-assembling a facial [(Tp)Fe(CN)(3)](-) [Tp = hydrotris(pyrazolyl)borate] precursor and respective Mn(iii) Schiff bases. X-Ray crystal structure analyses revealed that each complex is composed of a central Mn(iii) dimer doubly linked by phenoxides of the tetradentate N(2)O(2) Schiff bases and the terminal [(Tp)Fe(CN)(3)](-) groups connecting to the center through cyanides. Using the spin Hamiltonian H = -2J(1)(S(Fe1).S(Mn1) + S(Mn1a).S(Fe1a)) - 2J(2)(S(Mn1).S(Mn1a)), where J(1) stands for the exchange coupling constant between Fe(iii) (S(Fe) = 1/2) and Mn(iii) (S(Mn) = 2) through cyanides and J(2) between Mn(iii) ions via phenoxides, the best fits corresponded to J(1) = 2.61 cm(-1) and J(2) = 0.85 cm(-1) for , J(1) = 2.50 cm(-1) and J(2) = 1.30 cm(-1) for , and J(1) = -2.15 cm(-1) and J(2) = 0.55 cm(-1) for . The phenoxide routes transmit ferromagnetic interactions in all cases, while ferromagnetic or antiferromagnetic couplings occur through the cyanide linkage. Although the geometric parameters relevant to the magnetic Fe-C[triple bond, length as m-dash]N-Mn pathways are analogous to each other their magnetic natures are varied across the compounds, which supports that a degree of orbital overlap is quite sensitive to a subtle structural change in the present system.
authors.affiliation: Department of Chemistry, Korea University, Seoul 136-713, Korea.
authors.forename: Hyun Young
authors.initials: HY
authors.lastname: Kwak
authors.forename: Dae Won
authors.initials: DW
authors.lastname: Ryu
authors.forename: Hyoung Chan
authors.initials: HC
authors.lastname: Kim
authors.forename: Eui Kwan
authors.initials: EK
authors.lastname: Koh
authors.forename: Beong Ki
authors.initials: BK
authors.lastname: Cho
authors.forename: Chang Seop
authors.initials: CS
authors.lastname: Hong
mesh_terms: D018360:Crystallography, X-Ray; D003486:Cyanides / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D008280:Magnetics; D008345:Manganese / Q000737:chemistry*; D012545:Schiff Bases / Q000737:chemistry
chemical_list: D003486:Cyanides; D005290:Ferric Compounds; D012545:Schiff Bases; D008345:Manganese