Synthesis, X-ray Structures, and Fluorescent Properties of Coordination Networks Constructed from 2-(2-Pyridinyl-benzimidazolyl) Acetic Anion

Four new metal coordination polymers, [Cd(pybma)(2)](n) (1), [Zn(pybma)(C2O4)(0.5)center dot 0.5H(2)O](n) (2), [Co(pybma)(C2O4)(0.5)](n) (3), and [Zn-3(pybma)(2)(HBTC)(2)(H2O)(4)](n) (4) [pybma = 2-(2-pyridinyl-benzimidazolyl) acetic anion; H3BTC = 1,3,5-benzenetricarboxylate], have been synthesized under hydrothermal conditions and structurally characterized by element analyses, IR spectroscopy, and single-crystal X-ray diffraction analyses. 1 has a one-dimensional (1D) chain structure, which contains two kinds of rings. Interestingly, 2 has a two-dimensional (2D) metal-organic framework and can be seen as the unity of two parallel double-stranded helices, in which the helices are bridged by oxalate ligands. 3 has a 2D framework built from 1 D chains and ox bridges. 4 has 2D layer framework which is assembled into a three-dimensional (3D) framework with two kinds of channels. Polymers 1, 2, and 4 exhibit obvious fluorescent emissions in the solid state at room temperature; no fluorescent emission is observed in polymer 3.