Two 2D cadmium coordination polymers with 3,4-pyridinedicarboxylic acid

Two 2D cadmium coordination polymers {[Cd(pda)(2,2′-bpy)(H2O)] · H2O}n (1) and {[Cd(pda)(4,4′-bpy)(H2O)] · 2H2O}n (2) (H2pda = 3,4-pyridinedicarboxylic acid; 2,2′-bpy = 2,2′-bipyridine; 4,4′-bpy = 4,4′-bipyridine) have been synthesized and characterized by elemental analysis, infrared spectroscopy and X-ray single crystal diffraction. The 3D supramolecular structures of both 1 and 2 are constructed by hydrogen bonds between the 2D layers. Importantly, there are intramolecular π ⋯ π stacking interactions in both of the compounds. Crystallographic data for 1: Orthorhombic, Pbca, a = 15.5977(12) Å, b = 12.6063(10) Å, c = 16.9891(13) Å, Z = 8, R1 = 0.0202, wR2 = 0.0504; for 2: Monoclinic, C2/c, a = 27.345(4) Å, b = 11.2530(16) Å, c = 12.1068(16) Å, β = 104.197(2)°, Z = 8, R1 = 0.0269, wR2 = 0.0625.