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-poly[[[bis[diaquacadmium(II)]-mu(2)-trans-1,2-bis(4-pyridyl)ethene]bis{mu(2)-2,2'-[(5-carboxymethoxy-m-phenylene)dioxy]diacetato}] trans-1,2-bis(4-pyridyl)ethene solvate dihydrate], {[Cd(2)(C(12)H(10)O(9))(2)(C(12)H(10)N(2))(H(2)O)(4)].C(12)H(10)N(2).2H(2)O}(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).