Hydrothermal Syntheses and Characterizations of Three ZnII Coordination Polymers Tuned by pH Value and Base

Three new Zn-II coordination polymers, [Zn(bpe)(HL)(2)(H2O)](n) (1), {[Zn(bpe)(L)]center dot H2O}(n) (2), and [Zn2Ca(bpe)(HL)(2)(L)(2)](n) (3) [H2L, = 5-methoxyisophthalic acid and bpe = 1,2-dis(4-pyridyl) ethylene], were hydrothermally synthesized under different pH values and bases. Their structures were determined by single-crystal X-ray diffraction and further characterized by elemental analyses and IR spectroscopy. Polymer 1 is formed at pH = 4 and has a 1 D chain structure. These 1 D chains are linked by hydrogen bonds to afford a ID double chain and further to form a threefold interpenetrating network. At pH = 7, a 2D layer structure of 2 with sql topology is formed. By using calcium hydroxide as base for the synthesis of 3, a 3D network with pcu topology is obtained. These structural differences among 1-3 indicate that pH value and the identity of the base play important role in defining the overall structures of metalorganic frameworks. In addition, the fluorescent properties of 1-3 are discussed.