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]·H2O}n (M =
CoII (1), NiII (2), 0.3CoII + 0.7NiII (3); C4H4O52- = malate dianion, bipy = 4,4‘-bipyridine). The metal ions were interconnected
by α- and β-carboxylates of malate to produce infinite [M(C4H4O5)]n layers, which were further pillared by bridging bipy molecules
to form a 3D network. The μ3-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 antiferromagnetic interactions, while 2 is ferromagnetic, due to different electronic configurations
of the metal ions.