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

Five new Zn(II)/ODPT/bpe compounds, namely, {[Zn(bpe)(H 2 O) 2 ](H 2 ODPT)·3H 2 O} n ( 1 ), {[Zn 4 (ODPT) 2 (bpe) 3 (H 2 O) 2 ] 2 (bpe)·7H 2 O} n ( 2 ), {[Zn 2 (ODPT)(bpe) 2 ] 2 ·7H 2 O} n ( 3 ), {Zn 4 (ODPT) 2 (bpe)} n ( 4 ), and {Zn 2 (ODPT)(bpe)(H 2 O) 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 1D linear [Zn(bpe)(H 2 O) 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 (4·6 2 ·8 3 )(4 2 ·6 2 ·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 Zn 2+ and ODPT 4-, and further consolidated by the bpe ligands as molecular pillars. The most striking feature of 5 is that achiral ODPT 4– 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 C 222 1 . The diversity of the product structures illustrates the marked sensitivity of the coordination chemistry of the V-shaped multicarboxylate ligand (H 4 ODPT) to the pH value of the solution. Moreover, the thermal dynamic properties and fluorescent properties of all compounds are also investigated.