Hydrothermal Synthesis, Structures, and Photoluminescent Properties of Benzenepentacarboxylate Bridged Networks Incorporating Zinc(II)−Hydroxide Clusters or Zinc(II)−Carboxylate Layers

The first coordination compounds of partially or wholly deprotonated benzenepentacarboxylic acid (H₅L) were synthesized in the presence or absence of auxiliary 2,2‘-bipyridyl (2,2‘-bpy) and 1,10-phenanthroline (phen) ligands, and their crystal structures and photoluminescent properties were characterized. Their formulas are [Zn₆(μ₃-OH)₂(L)₂(H₂O)₆]_n (1), [Zn₅(μ₃-OH)₂(HL)₂(2,2‘-bpy)₂]_n (2), [Zn₂(HL)(phen)₂(H₂O)₂]_n (3), and [Zn₅(L)₂(phen)₄(H₂O)₃]_n·2nH₂O (4). Both 1 and 2 are three-dimensional (3D) zinc(II)−hydroxide cluster based coordination frameworks. 1 contains distorted chairlike hexanuclear Zn₆(μ₃-OH)₂ cluster units as secondary building blocks. Each Zn₆(μ₃-OH)₂ unit connects six others through the three-connected nodes of L^5- ligands into a 3D rigid and condensed coordination network, whereas in 2, each pentanuclear Zn₅(μ₃-OH)₂ unit connects the other six ones through the three-connected [HL]^4- nodes into a 3D network in the simple cubic packing mode. 3 has two-dimensional (2D) Zn(II)−carboxylate supramolecular layers constructed from a one-dimensional (1D) coordination chain structure by hydrogen bonds of the water and μ₅-[HL]^4- bridges, whereas 4 has 2D coordination layers composed of Zn(II) and μ₈-L^5- bridges. The adjacent coordination assemblies in 3 and 4 are further extended by hydrogen bonds and π···π interactions into 3D supramolecular architectures. 1−4 are photoluminescent active materials, and their photofluorescent properties are closely related to their intrinsic structure arrangements.