Structure characterization of several oxalate-bridged transition-metal coordination polymers

Four oxalate-bridged transit ion-metal supramolecular compounds [Co-2(im)(4)(ox)(2)] 1, [Co(im)(2)(ox)] 2, [Mn(2,2'-bpy)(ox)] 3 and [Fe(H2O)(2)(ox)] 4 (im, imidazole.: ox, oxalate; bpy, bipyridine) were obtained from the simple hydrothermal reactions of Mn+-ox-L (M, transition metal; L, aromatic N-donor ligand) system. They all exhibit the 1-D chain structures, consisting of the ML22+ (or ML2+) units linked by oxalate bridges. Interestingly, the 1-D oxalate chains in the title compounds are further self-assembled into the 3-D supramolecular networks through the interchain various secondary bonding interactions. Because the ML22+ units adopt the different configuration, the oxalate chains show either zigzag type as in compounds 1-3 or linear type as in compound 4. Compounds I and 2 are isomeric, and only in packing modes of interchain im molecules there exists the difference. (c) 2006 Elsevier B.V. All rights reserved.