Self-Catenated and Interdigitated Layered Coordination Polymers Constructed from Kinked Dicarboxylate and Organodiimine Ligands

Hydrothermal combination of divalent nickel or cobalt nitrates with the kinked carboxylic acid 4,4'-oxybis(benzoic acid) (H2oba) and the kinked and hydrogen-bonding capable organodiimine 4,4'-dipyridylamine (dpa) under basic conditions has afforded a pair of coordination polymers with a formulation of {[M(oba)(dpa)] x H2O} (M = Ni, 1; M = Co, 2). Both materials were characterized by single-crystal X-ray diffraction, infrared spectroscopy, and thermogravimetric analysis. The structures of 1 and 2 are isomorphous and manifest intriguing self-catenated two-dimensional layered motifs with very rare non-diamond 66 topology constructed from the direct covalent linkage of [M(oba)]n double helices through [M(dpa)]n undulating chains. Adjacent self-catenated layers engage in mutual interdigitation to form double-layer patterns that further aggregate via supramolecular hydrogen-bonding patterns imparted by the central amine of the dpa ligand. These coordination polymers are very thermally robust, with decomposition occurring only above 400 degrees C.