Synthesis, spectroscopic, and structural characterization of two malate zinc coordination polymers with imidazole or 2,2′-bipyridine

Abstract

Zinc(II) coordination polymers, [Zn(Hmal)(im)(H 2 O)] n Á 2nH 2 O (1) and [Zn(Hmal)(bpy)] n Á 3nH 2 O (2) (H 3 mal ¼ malic acid, im ¼ imidazole, bpy ¼ 2,2 0 -bipyridine), were synthesized from aqueous solution and characterized by elemental analyses, infrared and fluorescence spectra, thermogravimetric analyses, and single-crystal X-ray structural analyses. In 1, zinc is coordinated by imidazole, water, and tridentate malate in octahedral geometry. The -carboxy group of malate further bridges with the other zinc forming 1-D polymeric chains. A pair of 1-D chains self-assemble to generate a double chain by strong hydrogen bonds between imidazole and malate. Furthermore, neighboring pairs of double chains are extended to form the final 3-D framework through intermolecular hydrogen bonds. In 2, the malates link Zn in a bidentate-monodentate fashion to form spiral-shaped chains that extend into a 3-D supramolecular structure by -stacking interactions and intermolecular hydrogen bonds. Complex 1 exhibits strong fluorescence at room temperature.