Helicity-induced two-layered Cd(II) coordination polymers built with different kinked dicarboxylates and an organodiimidazole

A new ligand bis-(4-imidazol-1-yl-phenyl)-diazene (azim), incorporating an azo moiety at the center and two imidazole groups at the terminals has been designed and synthesized. Under solvothermal conditions, this ligand reacts with Cd(NO₃)₂·6H₂O and different angular aromatic dicarboxylates to form layered coordination polymers: Cd(azim)(bcp)]_n (1) and {Cd(azim)(oba)](H₂O)}_n (2) bcpH₂ = 1,3-bis-(4′-carboxy phenoxy)benzene; oba = 4,4′-oxybis(benzoate)]. Both 1 and 2 have been characterized by single-crystal X-ray diffraction technique, elemental analysis, PXRD and IR spectroscopy. The structure of each polymer looks like 2D grid where two layers are interpenetrated in a “cloth-like” topology. Both the structures contain single- and double-stranded helical coils where the pitches as well as the width are controlled by the carboxylate co-ligands. The hydrogen-bonding interactions between adjacent layers extend these structures to overall 3D supramolecular architectures.