Structural Transformations of Cobalt(II) Coordination Polymers Constructed from N,N′-Di-3-pyridyladipoamide and Tetracarboxylic Acids: Disentanglement upon Water Coordination

Hydrothermal reactions of N,N'-di-3-pyridyladipoamide (L) with 1,2,4,5-benzenetetracarboxylic acid (1,2,4,5-H(2)btec) in water without and with NaOH afforded [Co(L)(1,2,4,5-btec)(0.5)](n), 1, and [Co(L)(1,2,4,5-btec)(0.5)(H2O)(2)](n), 2, respectively, while immersion of 1 into water at room temperature gave {[Co(L)(0.5)(1,2,4,5-btec)(0.)(5)(H2O)(4)]center dot 2H(2)O)(n), 3, which have been structurally characterized. Complexes 1-3 display a 2-fold interpenetrated 3D framework, a unique 2D layer, and a 1D chain, respectively. While complexes 1 and 2 adopt the same point symbol of (4.6(4).8) 2 (4(2).6(2).8(2)) for nets, they differ in the vertex symbols that are [4.8(6).6.6.6.6][4.4.6(2).6(2).8(2).8(2)] and [4.8(10).6.6.6.6]-4.4.6(2).6(2).8(10).8(10)], respectively. Complexes 1-3 form a unique series of mixed-ligand coordination polymers that show 3-, 2-, and ID structures, respectively, and differ in the bonding mode of the anionic polycarboxylate as well as the conformations of the neutral L ligand. Irreversible and temperature-dependent structural changes from 1 to 2 and 3 are observed, demonstrating the disentanglement of 1 upon water coordination at various temperatures, which can be ascribed to the variable bonding mode of 1,2,4,5-btec(4-)( )and the flexible nature of L.