Three Cd(II) coordination polymers assembled by flexible 2,2′-azodibenzoic acid and N-donor auxiliary ligand: Structural diversities and luminescent properties

Hydrothermal reactions of Cd(OAc)2 · 2H2O with 2,2′-azodibenzoic acid (H2L) and three N-donor ancillary ligands in MeOH/H2O at 120 °C gave rise to three cadmium(II) coordination polymers [CdL(bpy)]n (1), {[Cd4L4(bpe)(H2O)2] · 2H2O}n (2) and [CdL(bpp)]n (3) [bpy = 4,4′-bipyridine, bpe = 1,2-bis(4-pyridyl)ethylene, bpp = 1,3-bis(4-pyridyl)propane]. Structural analysis reveals that compound 1 possesses a novel three-fold interpenetrating diamondoid framework constructed by linking Cd centers with L and pillared bpy ligands. Compound 2 comprises a 3D network with a rare Schläfli symbol of (446581)(4462), the 3D structure is built from 2D [CdL2]n nets and pillared bpe ligands. Compound 3 exhibits the same 66 topology with that of 1. Such a 3D architecture contains 1D helical [Cd(bpp)]n chains and [CdL]n chains along the a axis and b axis, respectively. The structural differences among 1–3 indicate that the N-donor ancillary ligands have significant effects on the formation of the final architectures. Photoluminescent properties of 1–3 in solid state were also investigated.