Syntheses, structures, and properties of trinuclear complexes [M(bpca)2{M′(hfaC)2}2], constructed with the complexed bridging ligand [M(bpca)2] [M, M′ = Ni(II), Mn(II); Cu(II), Mn(II); Fe(II), Mn(II); Ni(II), Fe(II); and Fe(II), Fe(II); hbpca = bis(2-pyridylcarbonyl)amine, hhfac = hexafluoroacetylacetone]

Five trinuclear complexes [M(bpca)(2){M'(hfac)(2)}(2)] (where MM'(2) = NiMn2, CuMn2, FeMn2, NiFe2, and FeFe2; Hbpca = bis(2-pyridyloarbonyl)amine; and Hhfac = hexafluoroacetylacetone) were synthesized almost quantitatively by the reaction of [M(bpca)(2)] and [M'(hfaC)(2)] in 1:2 molar ratio, and their structures and magnetic properties were investigated. Three complexes, with M' = Mn, crystallize in the same space group, Pna2(1), whereas two complexes, with M' = Fe, crystallize in P4(1), and complexes within each set are isostructural to one another, In all complexes, [M(bpca)(2)] acts as a bis-bidentate bridging ligand to form a linear trinuclear complex in which three metal ions are arranged in the manner W-M-W. The central metal ion is in a strong ligand field created by the N-6 donor set, and hence the Fe(II) in the {Fe(bpca)(2)} moiety is in a low-spin state. The terminal metal ions (M') are surrounded by O-6 donor sets with a moderate ligand field, which leads to the high-spin configuration of Fe(II). Three metal ions in all complexes are almost collinear, and metal-metal distances are ca. 5,5 Angstrom. The, magnetic behavior of NiMn2 and NiFe2 shows a weak ferromagnetic interaction between the central Ni(II) ion and the terminal Mn(II) or Fe(II) ions. In these complexes, sigma-spin orbitals of the central Ni(II) ion and those of terminal metal ions have different symmetry about a 2-fold rotation axis through the Ni-N-amide-M'(terminal) atoms, and this results in orthogonality between the neighboring sigma-spin orbitals and thus ferromagnetic interactions.