Polythreading of Infinite 1D Chains into Different Structural Motifs:  Two Poly(pseudo-rotaxane) Architectures Constructed by Concomitant Coordinative and Hydrogen Bonds

Two new compounds, [Co(4,4‘-bipy)(H₂O)₄]·(H₂bptc)·2H₂O (1) and [Ni(4,4‘-bipy)(H₂O)₄]·0.5(btc)·H₂O (2) (4,4‘-bipy = 4,4‘-bipyridine, H₄bptc = 3,3‘,4,4‘-biphenyltetracarboxylate acid, H₄btc = 1,2,4,5-benzenetetracarboxylate acid), have been synthesized under hydrothermal conditions and characterized by elemental analysis, IR, TG analysis, and single-crystal X-ray diffraction. X-ray structural analysis revealed that two different structural motifs (1D covalent zigzag chain and 1D hydrogen-bonded ladder for 1 and 1D linear chain and 2D hydrogen-bonded sheet for 2) can be found within their crystal structures, and most intriguingly, they coexist in such a way that 1D covalently bonded chains of composition [M(4,4‘-bipy)(H₂O)₄]²⁺ (M = Co or Ni) thread into the hydrogen-bonded 1D ladders or 2D sheets formed by uncoordinated carboxylate anions and lattice water molecules, giving rise to overall entangled architectures with unusual poly(pseudo-rotaxane)-type arrangements. Thermal stability of the two compounds was also studied in this paper.