Li-Hua Zhao

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.

Synthesis and characterization of biocompatible ZnO nanoparticles

ZnO nanoparticles are among the most promising emerging fluorescent labels for cellular imaging. However, there are only a few reports on the successful application of ZnO nanoparticles in biolabeling so far. The major problem of ZnO nanoparticles arises from their poor stability in water. In this work, two new facile synthesis methods were developed for fabricating water-stable ZnO nanoparticles, which have blue and yellow fluorescence and are expected to be of use for labeling different cellular structures simultaneously. Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectrometry (FT-IR), UV-vis, and fluorescence spectrophotometry (PL) were employed to investigate the structures and properties of ZnO nanoparticles. The mechanisms for the formation of the ZnO nanoparticles of both samples are analyzed. Furthermore, hemolysis assay was performed to evaluate the biocompatibility of these ZnO nanoparticlesin vitro. The biocompatibility of the ZnO nanoparticles, even at very high doses, ensures their potential in biomedical applications.

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.

Synthesis of water-soluble ZnO nanocrystals with strong blue emission via a polyol hydrolysis route

ZnO nanocrystals with strong blue emission have been synthesized via a facile polyol hydrolysis route. The as-synthesized ZnO nanocrystals were stable in water, even at basic or acidic aqueous conditions. The water stability of such ZnO nanocrystals was provided by the hydroxyl groups of triethylene glycol (TREG) and also the carboxyl group of oleic acid (OA) on their surfaces. We found that heat temperatures, heat times and concentrations of OA were all important factors that influence the particle size and the crystallinity of the ZnO nanocrystals. Interestingly, the photoluminescence properties of ZnO nanocrystals were not dependent on the particle size, but were attributed to the surface defects on ZnO which were closely related to the process of ZnO nanocrystals coated by TREG. Such ZnO water-disperse nanocrystals with intense blue fluorescence are expected to be of use for further practical applications, such as for the applications in biological fluorescence labelling.

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.

Synthesis of water-soluble γ-aminopropyl triethoxysilane-capped ZnO:MgO nanocrystals with biocompatibility

ZnO:MgO nanocrystals have been synthesized by a sequential preparative procedure and capped with γ-Aminopropyl triethoxysilane (APTES), thereby rendering the surface of the nanocrystals hydrophilic and the particles water-soluble. Orthogonal experiment was employed to optimize the correlated parameters of the reaction of capping ZnO:MgO nanocrystals with APTES. The effects of the quantity of APTES, reaction time, and reaction temperature on the aqueous stability of APTES-capped ZnO:MgO nanocrystals were investigated by orthogonal experiment and their optimal values were determined to be: 0.25 mmol, 60 min, and 25 °C, respectively. The water-soluble APTES-capped ZnO:MgO nanocrystals emit strongly in the visible region on excitation by UV radiation and are stable over extended periods. The aqueous-stability of the nanocrystals is attributed to the exposed hydrophilic groups (–NH2, –OH). Furthermore, hemolysis was performed to evaluate the biocompatibility of the nanocrystals. Hemolytic results indicate that APTES-capped ZnO:MgO nanocrystals have good biocompatibility, which is especially important for ensuring their potential in biomedical applications.

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.

Modulating the magnetization dynamics of four phenoxo-O bridged Dy2 complexes based on a Schiff base derived from 8-hydroxyquinoline

Four novel μ-O bridged dinuclear Dy2 clusters have been synthesized successfully by utilizing an 8-hydroxyquinoline (8-HQ) Schiff base ligand and four different co-ligands: [Dy2(bfa)2(L)2(H2O)2]·4CH3OH (1), [Dy2(TTA)2(L)2(H2O)2]·4CH3OH (2), [Dy2(acac)2(L)2(H2O)2]·2H2O (3) and [Dy2(PhCOO)2(L)2(H2O)2] (4) (Hbfa = benzoyl trifluoroacetylacetone, HTTA = thiophene trifluoroacetylacetone, Hacac = acetylacetone, PhCOOH = benzoic acid, H2L = 2-[(4-pyridinebenzoylhydrazone)methyl]-8-hydroxyquinoline). Magnetic studies show that only complex 1 exhibits SMM behavior under a zero dc field with a magnetic relaxation barrier of 68.89 K. When a dc field of 1500 Oe is applied, the value of ΔE/kB increases to 72.63 K. The different dynamic magnetic behaviors of the four Dy2 complexes mainly originate from the tiny changes of the coordination environment and magnetic coupling interaction of the central ions caused by the different co-ligands. Meanwhile, it proves that the co-ligands play an important role in modulating the magnetic properties of Dy-SMMs based on 8-HQ derivatives.