pH Influence on the Structural Variations of 4,4′-Oxydiphthalate Coordination Polymers

Five new Zn(II)/ODPT/bpe compounds, namely, {[Zn(bpe)(H2O)(2)](H2ODPT)center dot 3H(2)O}(n) (1), {[Zn-4(ODPT)(2)(bpe)(3)(H2O)(2)](2)(bpe)center dot 7H(2)O}(n) (2), {[Zn-2(ODPT)(bpe)(2)](2)center dot 7H(2)O}(n) (3), {Zn-4(ODPT)(2)(bpe)}(n) (4), and {Zn-2(ODPT)(bpe)(H2O)(2)}(n) (5) (ODPT = 4,4'-oxidiphthalate, bpe = 1,2-bis(4-pyridyl)ethane), have been synthesized through a hydrothermal method under different pH conditions, and characterized by single-crystal X-ray diffraction, element analysis, infrared spectra (IR), and thermogravimetric (TG) analyses. Compound 1 shows a 3D network framework constructed by the ID linear [Zn(bpe)(H2O)(4)](n)(2+) cationic chains through extensive hydrogen-bonding. Compound 2 displays an unusual three-dimensional (3D) meso-racemic self-penetrating coordination network with distinct chiral information in the interpenetrating networks. Compound 3 features a novel 4-connected (4 center dot 6(2)center dot 8(3))(4(2)center dot 6(2)center dot 8(2)) topology, also exhibiting an intriguing 3D self-penetrating structure formed by triple- and double-stranded helical chain motifs. Compounds 4 and 5 are based upon 3D pillared-layer frameworks constructed from Zn2+ and ODPT4-, and further consolidated by the bpe Ligands as molecular pillars. The most striking feature of 5 is that achiral ODPT4- ligands link the Zn cations into right-handed 2(1) helical chains, and the chiral information is transferred to the 3D framework with a chiral space group C222(1). The diversity of the product structures illustrates the marked sensitivity of the coordination chemistry of the V-shaped multicarboxylate ligand (H4ODPT) to the pH value of the solution. Moreover, the thermal dynamic properties and fluorescent properties of all compounds are also investigated.