μ-4,4′-Bipyridine-κ²N:N′-bis[triaqua(4,4′-bipyridine-κN)cadmium(II)] bis(3-aminobenzoate) bis(perchlorate) dihydrate: a novel supramolecular system constructed by π–π and hydrogen-bonding interactions

The title dicadmium compound, [Cd₂(C₁₀H₈N₂)₅(H₂O)₆](C₇H₆NO₂)₂(ClO₄)₂·2H₂O, is located around an inversion centre. Each Cd^II centre is coordinated by three N atoms from three different 4,4′-bipyridine ligands and three O atoms from three coordinating water molecules in a distorted octahedral coordination environment. In the dicadmium cation unit, one 4,4′-bipyridine (4,4′-bipy) molecule acts as a bidentate bridging ligand between two Cd metal ions, while the other four 4,4′-bipy molecules act only as monodentate terminal ligands, resulting in a rare `H-type' [Cd₂(C₁₀H₈N₂)₅(H₂O)₆] host unit. These host units are connected to each other viaπ–π stacking interactions, giving rise to a three-dimensional supramolecular grid network with large cavities. The 3-aminobenzoate anions, perchlorate anions and water molecules are encapsulated in the cavities by numerous hydrogen-bonding interactions. To the best of our knowledge, this is the first example of a coordination compound based on both 4,4′-bipyridine ligands together with discrete 3-aminobenzoate anions.