Synthesis and crystal structure of a cadmium(II) coordination polymer based on 4,4′-(1H-1,2,4-triazole-3,5-di­yl)dibenzoate

The asymmetric unit of the title compound, catena-poly[[[aqua­bis­(pyridine-κN)cadmium(II)]-μ₂-4,4′-(1H-1,2,4-triazole-3,5-di­yl)dibenzoato-κ⁴O,O′:O′′,O′′′] 4.5-hydrate], {[Cd(C₁₆H₉N₃O₄)(C₅H₅N)₂(H₂O)]·4.5H₂O}n or {[Cd(bct)(py)₂(H₂O)]·4.5H₂O}_n (I), consists of a Cd²⁺ cation coordinated to one bct^2– carboxyl­ate dianion, two mol­ecules of pyridine and a water mol­ecule as well as four and a half water mol­ecules of crystallization. The metal ion in I possesses a penta­gonal–bipyramidal environment with the four O atoms of the two bidentately coordinated carboxyl­ate groups and the N atom of a pyridine mol­ecule forming the O₄N equatorial plane, while the N atom of another pyridine ligand and the O atom of the water mol­ecule occupy the axial positions. The bct^2– bridging ligand connects two metal ions via its carb­oxy­lic groups, resulting in the formation of a parallel linear polymeric chain running along the [1 | 1] direction. The coordinated water mol­ecule of one chain forms a strong O—H⋯O hydrogen bond with the carboxyl­ate O atom of a neighboring chain, leading to the formation of double chains with a closest distance of 5.425 (7) Å between the cadmium ions belonging to different chains. Aromatic π–π stacking inter­actions between the benzene fragments of the anions as well as between the coordinated pyridine mol­ecules belonging to different chains results in the formation of sheets oriented parallel to the ( | 01) plane. As a result of hydrogen-bonding inter­actions involving the water mol­ecules of crystallization, the sheets are joined together in a three-dimensional network.