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

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 = 1.7421（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 architeeture. 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）.