Novel topological supramolecular architectures based on partially protonated butane-1,2,3,4-tetracarboxylato complexes: Synthesis, structures and magnetic properties

• 1 represents a rare topological example of 2D → 3D interlocking systems.
• 2 and 3 all exhibit a (3,4)-connected novel network topology.
• The magnetic characterizations suggest π–π stacking interactions to be effective pathways.

This work presents three supramolecular complexes with partially protonated butane-1,2,3,4-tetracarboxylato ligand [Ni2(phen)4(H2BUTC)]·2H3BUTC·6H2O 1, [Cu(phen)2(H2BUTC)]·5H2O 2 and [Cu(bpy)2(H(HBUTC)2/2)]·H2O 3 (H4BUTC = butane-1,2,3,4-tetracarboxylic acid, phen = 1,10-phenanthroline and bpy = 2,2′-bipydine). Compound 1 represents a first example of coordination compounds with the tri-protonated butane-1,2,3,4-tetracarboxylate anion. The 2D cation supramolecular layer could be described as a 2D 3-connected honeycomb network, and the 3D anion supramolecular architecture can be considered to be a planar and tetrahedral binodal Mog network. The 2D cation layer inserts into the 3D anionic supramolecular architecture to form the rare interpenetrating network. In 2, the Cu(phen)2(H2BUTC) units are linked by hydrogen bonding interactions to a 1D double-chain, which are engaged in π–π stacking interactions leading to (3,4)-connected 3D supramolecular architecture with the Schläfli symbol of (42·6·82·10)(82·10). The compound 3 exhibits a rare 1D symmetric-hydrogen-bond-chain, the resulting chains are via hydrogen bonding and π–π stacking interactions to 3D (3,4)-connected network with the Schläfli symbol of (63)(65⋅8). The magnetic susceptibility data of 1–3 all obey the Curie–Weiss law, and the variable temperature magnetic characterizations on 1–3 suggest weak antiferromagnetic coupling exchange.

Graphic abstractThe characteristic building blocks of the new complexes [Ni2(phen)4(H2BUTC)]·2H3BUTC·6H2O 1, [Cu(phen)2(H2BUTC)]·5H2O 2 and [Cu(bpy)2(H(HBUTC)2/2)]·H2O 3 are the [HnBUTC](4−n)-bridged [M(NN)2] moieties into novel 3D supramolecular architecture with multi-nodal topological net. The magnetic behaviors of 1–3 suggest weak antiferromagnetic couplings.Figure optionsDownload as PowerPoint slide