Two 3D CdII and ZnII Complexes Based on Flexible Dicarboxylate Ligand and Nitrogen-containing Pillar: Synthesis, Structure, and Luminescent Properties

Two 3D isomorphous and isostructural complexes, namely, [Zn(BDOA)(bpy)(H2O)(2)](n) (1) and [Cd(BDOA)(bpy)(H2O)(2)](n) (2); (BDOA = Benzene-1,4-dioxyacetic acid, bpy = 4,4'-bipyridine) were synthesized under hydrothermal conditions and characterized by means of elemental analyses, thermogravimetric (TG), infrared spectrometry, and single crystal X-ray diffraction. Complexes 1 and 2 crystallize in the triclinic system, space group P-1 and each metal ion in the complexes are six-coordinated with the same coordination environment. In the as-synthesized complexes, BDOA(2-) anions link central metal ions to form a 1D zigzag chain [-BDOA(2-)-Zn(Cd)-BDOA(2-)-Zn(Cd)-](infinity), whereas bpy pillars connect metal ions to generate a 1D linear chain [-bpy-Zn(Cd)-bpy-Zn(Cd)-](infinity). Both infinite chains are interweaved into 2D grid-like layers which are further constructed into a 3D open framework, where hydrogen bonds play as the bridges between the adjacent 2D layers. Luminescent properties of complex 1 showed selectivity for Hg2+ ion.