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]