Novel cup-like helical coordination polymers: synthesis, crystal structures and thermal properties

By the design of ligand 1,1′-(1,5-pentamethylene)bis-1H-benzimidazole (pbbm), we have synthesized polymers {[Co(NO3)(pbbm)2]NO3 · 1/2H2O}n (1), {[CdCl(pbbm)2]Cl · CH3OH}n (2) and {[Cu(Ac)2(pbbm)] · CH3OH}n (3), and characterized their structures by single crystal X-ray diffraction as well as thermoanalysis. In polymers 1 and 2, one of the anions coordinates to the central ion, the other is located in the environment. Two pbbm ligands coordinate simultaneously to two metal centers generating one-dimensional cup-like helical chains. To our best knowledge, this cup-like structure has never been observed in the reported polymers. In polymer 3, each Cu atom is five-coordinate by two nitrogen atoms from two pbbm ligands, and three oxygen atoms from one monodentate acetate anion and one chelating acetate anion leading to one-dimensional wave-like linear chain. In addition, the DTA and TG results of the three polymers are in agreement with the crystal structures.