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

Five new Zn­(II)/ODPT/bpe compounds, namely, {[Zn­(bpe)­(H<sub>2</sub>O)<sub>2</sub>]­(H<sub>2</sub>ODPT)·3H<sub>2</sub>O}<sub><i>n</i></sub> (<b>1</b>), {[Zn<sub>4</sub>(ODPT)<sub>2</sub>(bpe)<sub>3</sub>(H<sub>2</sub>O)<sub>2</sub>]<sub>2</sub>(bpe)·7H<sub>2</sub>O}<sub><i>n</i></sub> (<b>2</b>), {[Zn<sub>2</sub>(ODPT)­(bpe)<sub>2</sub>]<sub>2</sub>·7H<sub>2</sub>O}<sub><i>n</i></sub> (<b>3</b>), {Zn<sub>4</sub>(ODPT)<sub>2</sub>(bpe)}<sub><i>n</i></sub> (<b>4</b>), and {Zn<sub>2</sub>(ODPT)­(bpe)­(H<sub>2</sub>O)<sub>2</sub>}<sub><i>n</i></sub> (<b>5</b>) (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 <b>1</b> shows a 3D network framework constructed by the 1D linear [Zn­(bpe)­(H<sub>2</sub>O)<sub>4</sub>]<sub><i>n</i></sub><sup>2+</sup> cationic chains through extensive hydrogen-bonding. Compound <b>2</b> displays an unusual three-dimensional (3D) meso-racemic self-penetrating coordination network with distinct chiral information in the interpenetrating networks. Compound <b>3</b> features a novel 4-connected (4·6<sup>2</sup>·8<sup>3</sup>)­(4<sup>2</sup>·6<sup>2</sup>·8<sup>2</sup>) topology, also exhibiting an intriguing 3D self-penetrating structure formed by triple- and double-stranded helical chain motifs. Compounds <b>4</b> and <b>5</b> are based upon 3D pillared-layer frameworks constructed from Zn<sup>2+</sup> and ODPT<sup>4‑</sup>, and further consolidated by the bpe ligands as molecular pillars. The most striking feature of <b>5</b> is that achiral ODPT<sup>4–</sup> ligands link the Zn cations into right-handed 2<sub>1</sub> helical chains, and the chiral information is transferred to the 3D framework with a chiral space group <i>C</i>222<sub>1</sub>. The diversity of the product structures illustrates the marked sensitivity of the coordination chemistry of the V-shaped multicarboxylate ligand (H<sub>4</sub>ODPT) to the pH value of the solution. Moreover, the thermal dynamic properties and fluorescent properties of all compounds are also investigated.