Four one-dimensional cadmium(II) polymers: one chairlike chain containing four azido bridging modes and three double end-on azido-bridged uniform chains

Four new azido-bridged cadmium(II) complexes have been synthesized and characterized by spectroscopy and crystallographic methods. Compounds [Cd-3(L-1)(2)(N-3)(6)(H2O)(CH3OH)(0.5)](n) (1), [Cd(L-2)(N-3)(2)](n) (2), [Cd-2(L-3)(DMF)(N-3)(4)](n) (3) and [Cd(L-4)(N-3)(2)](n) (4) (L-1=2-acetylpyridine,L-2=2-(pyrazol-1-ylmethyl) pyridine, L-3=2-(3-methylpyrazol-1-ylmethyl) pyridine and L-4=1-(2-pyridyl)-2-aza-1-amylene) show one-dimensional (1-D) polymeric structures in the lattice with the distorted octahedral coordination environment of the cadmium(II) ions in the four complexes. Compound 1 contains hexanuclear chairlike unit with defective dicubane-like core, which is further linked by azido bridges into a novel 1-D chain. It is interesting that four different azido bridging modes exist simultaneously in 1. Zigzag chains with double end-on (EO) azido bridged Cd(II) ions are formed in compound 2. Compounds 3 and 4 consist of uniform double EO azido bridged helical chains with screw-pitches of 18.91 and 26.04 Angstrom, respectively. It should be noted that the longer pitch in 4 is unusual in inorganic-organic hybrid complexes. Further comparison within the four chains shows that the rigidity of the chains increases with the steric effect of the co-ligands coordinated to the central Cd(II) ions.