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

Abstract

Four new azido-bridged cadmium(II) complexes have been synthesized and characterized by spectroscopy and crystallographic methods. Compounds [Cd₃(L¹)₂(N₃)₆(H₂O)(CH₃OH)_0.5]_n (1), [Cd(L²)(N₃)₂]_n (2), [Cd₂(L³)(DMF)(N₃)₄]_n (3) and [Cd(L⁴)(N₃)₂]_n (4) (L¹ = 2-acetylpyridine, L² = 2-(pyrazol-1-ylmethyl)pyridine, L³ = 2-(3-methylpyrazol-1-ylmethyl)pyridine and L⁴ = 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 Å, 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.