Dipyridylamide isomer influenced dimensionality in luminescent cadmium phthalate coordination polymers with similar tetranuclear clusters and ribbon motifs

Hydrothermal reaction of cadmium nitrate, potassium hydrogen phthalate (KHphth), and either 4-pyridylnicotinamide (4-pna) or 3-pyridylisonicotinamide (3-pina) afforded two new luminescent coordination polymers with similar structural components but different dimensionality. {[Cd2(phth)2(4-pna)(H2O)]·0.25H2O}n (1, phth = phthalate) manifests [Cd4(phth)4(H2O)2] ribbons based on tetranuclear clusters, connected to two others by pairs of tethering 4-pna ligands to afford 4-connected 2D (4,4) layers. [Cd2(phth)2(3-pina)(H2O)]n (2) has similar tetranuclear clusters and [Cd4(phth)4(H2O)2] ribbons, which are linked to four others by 3-pina tethers to construct a 6-connected 3D 41263 pcu network. Subtle differences in phth binding and bridging mode, along with changes in coordination environment, serve to influence the dimensionality of the resulting coordination polymer. Thermal decomposition behavior is also discussed.