Synthesis and Properties of a One-Dimensional Mixed-Ligand Cd(Ⅱ) Complex with Helical Structure

摘要

The title complex, [[Cd(Him)(OH-BDC)(H2O)2]·3H2O]n (1) (Him is imidazole, OH-H2BDC is 5-hydroxyisophthalic acid), was synthesized by liquid/liquid diffusion method at room temperature. The complex crystallizes in orthorhombic, space group P212121, with a=0.671 6(7), b=1.380 6(2), c=1.742 1(2) nm, V=1.615 2(3) nm3, C11H18CdN2O10, Mr=450.67, Dc=1.853 g/cm3, μ=1.407 mm-1, F(000)=904, Z=4, the final R1=0.020 9 and wR2=0.045 3 for 3 211 observed reflections (I>2σ(I)). In the structure of 1, the OH-BDC ligands exhibiting bis-bidentate coordination mode bridge the adjacent Cd centers to form a one-dimensional helical chain and the second ligand Him acting as terminal ligands are attached to the helical chain. It is notable that a series of complicated hydrogen bonds (e.g., N—H…O, O—H…O) exist in the structure, which link neighboring helices into a three-dimensional supramolecular architecture. An observed intense blue luminescence with an emission band peaking at 390 nm for 1 may be resulted from ligand-to-metal charge transfer (LMCT).