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

The asymmetric unit of the title compound, catena -poly[[[aqua-bis-(pyridine-κ N )cadmium(II)]-μ 2 -4,4'-(1 H -1,2,4-triazole-3,5-di-yl)dibenzoato-κ 4 O , O ': O '', O '''] 4.5-hydrate], {[Cd(C 16 H 9 N 3 O 4 )(C 5 H 5 N) 2 (H 2 O)]·4.5H 2 O} n or {[Cd(bct)(py) 2 (H 2 O)]·4.5H 2 O} n ( I ), consists of a Cd 2+ cation coordinated to one bct 2- carboxyl-ate dianion, two mol-ecules of pyridine and a water mol-ecule as well as four and a half water mol-ecules of crystallization. The metal ion in I possesses a penta-gonal-bipyramidal environment with the four O atoms of the two bidentately coordinated carboxyl-ate groups and the N atom of a pyridine mol-ecule forming the O 4 N equatorial plane, while the N atom of another pyridine ligand and the O atom of the water mol-ecule occupy the axial positions. The bct 2- bridging ligand connects two metal ions via its carb-oxy-lic groups, resulting in the formation of a parallel linear polymeric chain running along the [11] direction. The coordinated water mol-ecule of one chain forms a strong O-H⋯O hydrogen bond with the carboxyl-ate 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 inter-actions between the benzene fragments of the anions as well as between the coordinated pyridine mol-ecules belonging to different chains results in the formation of sheets oriented parallel to the (01) plane. As a result of hydrogen-bonding inter-actions involving the water mol-ecules of crystallization, the sheets are joined together in a three-dimensional network.