Synthesis and characterization of expected and unexpected topologies of homochiral porous metal(II) malate frameworks

Three new homochiral metal–organic frameworks (MOFs) based on malate anions and N-donor linkers of different length have been prepared. [Co2(mal)2(bpy)]·2H2O (1), [Ni2(mal)2(bpy)]·2H2O (2), [Ni2(mal)2(bpe)]·3H2O (3) (mal = S-malate, bpy = 4,4′-bipyridyl, bpe = trans-1,2-bis(4-pyridyl)ethylene) were characterized by a number of analytical methods including single crystal X-ray analysis. Optical purity of compounds 2 and 3 was confirmed by polarimetry experiments. Compounds 1 and 2 contribute to the family of isoreticular M(II) malates and aspartates ([M2(asp)2L] and [M2(mal)2L], M = Cu, Co, Ni; L = ditopic rigid organic ligand) where all structural units (metal cations, chiral ligands and bridging ligands) could be changed with retention of the topology in the resulting framework. Compound 3 has a different structure and contributes to a different family of isoreticular homochiral MOFs.