3D Coordination Polymers with Nitrilotriacetic and 4,4‘-Bipyridyl Mixed Ligands:  Structural Variation Based on Dinuclear or Tetranuclear Subunits Assisted by Na−O and/or O−H···O Interactions

The reactions of Cu(II) with the mixed nitrilotriacetic acid (H3NTA) and 4,4‘-bipyridyl (4,4‘-bpy) ligands in different metal-to-ligand ratios in the presence of NaOH and NaClO4 afforded two complexes, Na3[Cu2(NTA)2(4,4‘-bpy)]ClO4·5H2O (1) and [Cu2(NTA) (4,4‘-bpy)2]ClO4·4H2O (2). The two complexes have been characterized by elemental analysis, IR, XRD, and single-crystal X-ray diffraction. 1 contains a basic doubly negatively charged [Cu2(NTA)2(4,4‘-bpy)]2- dinuclear unit which was further assembled via multiple Na−O and O−H···O interactions into a three-dimensional (3D) pillared-layer structure. 2 features a two-dimensional (2D) undulated brick-wall architecture containing a basic doubly positively charged [Cu4(NTA)2(4,4‘-bpy)2]2+ tetranuclear unit. The 2D network possesses large cavities hosting guest molecules and was further assembled via O−H···O hydrogen bonds into a 3D structure with several channels running in different directions.