An unusual polycatenating network self‐assembled by the 2D → 2D parallel → 3D parallel interpenetration of coordinative and hydrogen‐bonded (6,3) motifs

In the title coordination compound, catena‐polybisdiaquacadmium(II)]‐μ₂‐trans‐1,2‐bis(4‐pyridyl)ethene]bis{μ₂‐2,2′‐(5‐carboxymethoxy‐m‐phenylene)dioxy]diacetato}] trans‐1,2‐bis(4‐pyridyl)ethene solvate dihydrate], {Cd₂(C₁₂H₁₀O₉)₂(C₁₂H₁₀N₂)(H₂O)₄]·C₁₂H₁₀N₂·2H₂O}_n, (I), each Cd^II centre adopts a pentagonal–bipyramidal coordination geometry. The incompletely deprotonated 2,2′‐(5‐carboxymethoxy‐m‐phenylene)dioxy]diacetate (TCMB) ligands and trans‐1,2‐bis(4‐pyridyl)ethene (bpe) ligands both act as bidentate bridges, linking the Cd^II centres into one‐dimensional ladders, which are connected into an undulating two‐dimensional (6,3) layer through O—H...N hydrogen bonds between the carboxylate groups of the TCMB ligands and the N atoms of the uncoordinated bpe ligands. Each undulating layer polycatenates two other identical layers, exhibiting the unusual combination of both 2D → 2D parallel and 2D → 3D parallel interpenetration (2D and 3D are two‐ and three‐dimensional, respectively).