Syntheses, structures, and magnetic properties of three novel metal-malate-bipyridine coordination polymers with layered and pillared topology

The combination of metal ions with malic acid (hydroxybutane diacid) and 4,4'-bipyridine ligands under hydro(solvo)thermal conditions has resulted in the formation of three novel coordination polymers {[M(C4H4O5)(bipy)(0.5)]center dot H2O}(n) (M = Co-II (1), Ni-II (2), 0.3Co(II) + 0.7Ni(II) (3); C4H4O52- = malate dianion, bipy = 4,4'-bipyridine). The metal ions were interconnected by alpha- and beta-carboxylates of malate to produce infinite [M(C4H4O5)](n) layers, which were further pillared by bridging bipy molecules to form a 3D network. The mu(3)-malate ligand exhibits a pentadentate coordination mode, with all of the five oxygen atoms participating in the coordination. The magnetic pathways of three compounds are through M-O-C-O-M with nonplanar skew-skew conformations; compound 1 shows anti ferromagnetic interactions, while 2 is ferromagnetic, due to different electronic configurations of the metal ions.