Ligand and pH-Controlled Zn^II Bilayer Coordination Polymers Based on Biphenyl-3,3‘,4,4‘-tetracarboxylate

Abstract

Four novel Zn II coordination polymers, [Zn(btc) 0.5 (H 2 O)] n ( 1 ), {[Zn(btc) 0.5 (4,4‘-bpy) 0.5 (H 2 O)]·1.5H 2 O} n ( 2 ), {[Zn 2 (H 2 btc) 2 (4,4‘-bpy) 4 ]·H 2 O} n ( 3 ), [Zn(H 2 btc)(bpe)] n ( 4 ) [H 4 btc = biphenyl-3,3‘,4,4‘-tetracarboxylic acid, 4,4‘-bpy = 4,4‘-bipyridine, and bpe = 1,2-bis(4-pyridyl)ethane], have been synthesized by hydrothermal reactions. Single-crystal X-ray structural analysis reveals that the four polymers exhibit different novel bilayer architectures. Complex 1 possesses a bilayer structure in which two helical layers are further pillared by (btc) 4- ligands into a two-dimensional (2D) bilayer network. Complex 2 is an unusual 2D double-layered supramolecular motif generated by hydrogen bonding interactions of two single-layered networks. Complex 3 displays a 2D supramolecular bilayer network formed by the one-dimensional {[Zn 2 (H 2 btc) 2 (4,4‘-bpy) 4 ]·H 2 O} n polymer. Complex 4 features a 2D double-layered framework in which two puckering single layers are linked by μ 2 -carboxylato groups of (H 2 btc) 2- anions. The diverse structures illustrate rational adjustment of the second ligand, and the pH value is a good method to further design bilayer metal−organic compounds with novel structures and properties. In addition, the thermal stabilities and photoluminescence properties of 1 − 4 were also studied.