Ai-Hong Yang

Syntheses, structures, and photoluminescence of lanthanide coordination polymers with pyridine-2,3,5,6-tetracarboxylic acid

Six lanthanide(III) coordination polymers with the formulae {[Ln(Hpdtc)(H2O)3]·H2O}n [Ln = La (1), Ce (2), Pr (3)], {[Ln(Hpdtc)(H2O)2]·2H2O}n [Ln = Eu (4), Tb (5)] and {SmK(pdtc)(H2O)4}n (6) (H4pdtc = pyridine-2,3,5,6-tetracarboxylic acid) have been synthesized by reacting the corresponding rare earth salts or oxides with H4pdtc under hydrothermal conditions. In the three kinds of structure, H4pdtc displays three different coordination modes. H4pdtc is an elegant ligand with rich coordination sites and low symmetry, but has seldom been used to synthesize complexes. 1–6 are the first examples from lanthanide ions and H4pdtc. Furthermore, the novel wave-like T3(2)4(2)6(2) water tape with (H2O)4 as the substructure is present in complex 6. The two complexes of Eu(III) and Tb(III) exhibit the corresponding characteristic luminescence.

Novel lanthanide coordination polymers based on bis-tridentate chelator pyrazine-2,3,5,6-tetracarboxylate with nano-channels and water clusters

Three novel lanthanide coordination polymers with large channels and water clusters, [Yb2(pztc)1.5(H2O)6]·7H2O (1), [Lu2(pztc)1.5(H2O)6]·7.5H2O (2) and [Er2(pztc)1.5(H2O)6]·7H2O (3), have been synthesized by the reactions of pyrazine-2,3,5,6-tetracarboxylic acid (H4pztc) and Ln(III) salts in aqueous solution at room temperature or under hydrothermal conditions, and characterized by X-ray crystallography, elemental analysis, IR, UV-vis and thermal gravimetric analysis (TGA). Single crystal X-ray diffraction determination indicates that the Ln(III) ions were coordinated by three tridentate cheated pztc4− ligands and bis-tridentate cheated pztc4− ligands bridged Ln(III) ions to form hexanuclear metal ring structures with nano-channels which were filled with (H2O)14clusters.

ds-Block metal ions catalyzed decarboxylation of pyrazine-2,3,5,6-tetracarboxylic acid and the complexes obtained from hydrothermal reactions and novel water clusters

The factors that influence the decarboxylation of pyrazine-2,3,5,6-tetracarboxylic acid (H4pztc) under hydrothermal conditions were investigated. Higher temperature and lower pH are very effective promoters for the decarboxylation of H4pztc in the presence of ds-block metal ions. Four novel complexes of H4pztc and four complexes from the decarboxylation of H4pztc, [Zn2(pz25dc)(phen)4](NO3)2·10H2O (1), [Zn2(pztc)(phen)4]·12H2O (2), {[Zn2(pztc)(bpy)2(H2O)2]·2H2O}n (3), [Cu2(pz25dc)(phen)4](NO3)2·10H2O (4), {[Cu2(pztc)(bpy)2 H2O]·4H2O}n (5), [Cu2(H2pztc)(bpy)2(H2O)2](NO3)2·2H2O (6), [Cd(pz26dc)(phen)(H2O)2] (7) and [Cd(pz26dc)(bpy)(H2O)2] (8) (pz25dc = pyrazine-2,5-dicarboxylate, pz26dc = pyrazine-2,6-dicarboxylate, phen = 1,10-phenanthroline, bpy = 2,2′-bipyridyl) have been synthesized and characterized by X-ray single crystal diffraction, elemental analysis, IR, thermal gravimetric analysis (TGA) and fluorescence measurement. 1, 2, 4 and 6 are dinuclear complexes bridged by pztc or pz25dc, 3 and 5 are 1D coordination polymers. In 6, the Cu(II) ions are bridged by bis-tridentate H2pztc2−. 7 and 8 are mononuclear Cd(II) complexes. The 2D or 3D supramolecular structures of 1–8 were built up by hydrogen bonds and π⋯π interactions. Notably, a novel T5(0)A0 water tape and a S-shaped (H2O)10cluster are observed in 2 and 5, respectively.

Syntheses and crystal structures of two new nickel(II) complexes with pyrazine-2,3,5,6-tetracarboxylate

Pyrazine-2,3,5,6-tetracarboxylic acid (H4pztc) reacted with Ni(ClO4)2·6H2O and 1,10-phenanthroline (phen) in aqueous solutions to form two different complexes, [Ni(H2pztc)(phen)H2O]·H2O (1), [Ni(phen)3](H2pztc)·10.5H2O (2), under hydrothermal conditions and at room temperature respectively. In 1, Ni(II) ion is coordinated by tridentate chelated H2pztc2−. The carboxyl and carboxylate groups of H2pztc2− are roughly coplanar with the pyrazine ring and form intramolecular hydrogen bonds. While in 2, H2pztc2− remains uncoordinated, the carboxyl and carboxylate groups of H2pztc2− are out of plane of the pyrazine ring and do not form intramolecular hydrogen bonds. H2pztc2− and water molecules form negatively-charged channels and the channels are filled with [Ni(phen)3]2+ in the 3D supramolecular structure of 2. In addition, a novel water tape is present in 2.

1-D zigzag copper(II) complex with pyrazine-2,3,5,6-tetracarboxylate and oxalate

A 1-D zigzag coordination polymer, {[Cu2(H2pztc)(ox)(bpy)2] · 8H2O} n (1) (H4pztc = pyrazine-2,3,5,6-tetracarboxylic acid, ox = oxalate, bpy = 2,2′-bipyridine), has been synthesized under hydrothermal conditions. X-ray single crystal diffraction analysis indicates that the structure of the complex belongs to triclinic system, P 1 space group with a = 9.6085(19) Å, b = 10.111(2) Å, c = 11.009(2) Å, α = 99.41(3)°, β = 102.87(3)°, γ = 114.55(3)°, V = 907.9(3) Å3, Z = 1. Cu(II) is six coordinate by H2pztc2−, bpy, and ox2−, the oxalate produced from decarboxylation of H4pztc. [Cu2(ox)(bpy)2(H2O)2(NO3)2] (2) was also obtained from filtrate after 1 separated.

1-D zigzag double-chain coordination polymers of transition metals derived from pyridine-2,3,5,6-tetracarboxylic acid

Three new 1-D zigzag coordination polymers {[M2(pdtc)(bpy)2(H2O)3] · 4H2O} n [M = Zn (1), Ni (2), Co (3)] (H4pdtc = pyridine-2,3,5,6-tetracarboxylic acid, bpy = 2,2′-bipyridine) have been synthesized by the reactions of H4pdtc and corresponding metal salts in the presence of bpy at room temperature and characterized by elemental analyses, IR, TGA, fluorescence, and X-ray diffraction. The main structural feature of 1–3 is the presence of octahedrally coordinated M1(II) and M2(II) centers sequentially bridged by pdtc ligands; bpy acts as a blocking ligand to avoid further polymerization. These coordination modes lead to 1-D double-chain structures. The 2-D or 3-D supramolecular structures of 1–3 are built up by π ··· π and hydrogen-bond interactions. Two (H2O)3 clusters are observed in 1–3. The zinc complex shows strong fluorescent emission at 325 nm.