Properties of meso-tetrakis (4- n -alkanoyloxyphenyl) porphyrin liquid crystal Co and Ni complexes

Six series of meso-tetrakis (4-n-alkanoyloxyphenyl) porphyrin Co and Ni complexes (12 kinds) were reported. Nine of the compounds were found to exhibit liquid crystal properties and display a hexagonal columnar discotic columnar (Col_h) phase. Molecular structure of all synthesized compounds was confirmed by IR, UV, MS, ¹H NIVR, and elemental analysis. These liquid crystalline compounds have been studied by cyclic voltammetry, luminescence, and surface photovoltage spectroscopy. Supported by the National Natural Science Foundation of China (Grant No. 59783001), the Natural Science Foundation of Shandong Province (Grant No. Y2006B41), the Foundation of Shandong Provincial Education Department (Grant No. J06A53), the Natural Science Foundation of Shandong University of Technology (Grant No. 2004KJM15) and Doctor Foundation of Shandong University of Technology     

Sulfonate-based fluorescent probes for imaging hydrogen peroxide in living cells

Based on the mechanism of H₂O₂-mediated hydrolysis of sulfonates, two fluorescein disulfonates compounds (FS-1 and FS-2) were designed and synthesized as the highly selective and sensitive fluorescent probes for imaging H₂O₂ in living cells. The probes were detected with elemental analysis, IR, ¹H NMR and ¹³C NMR. Upon reaction with H₂O₂, the probes exhibit strong fluorescence responses and high selectivity for H₂O₂ over other reactive oxygen species and some biological compounds. Furthermore, the sulfonate-based probes, as novel fluorescent reagents, are cell-permeable and can detect micromolar changes in H₂O₂ concentrations in living cells by using confocal microscopy. Supported by the National Basic Research Program of China (Grant No. 2007CB936000), the National Natural Science Funds for Distinguished Young Scholar (Grant No. 20725518), Major Program of the National Natural Science Foundation of China (Grant No. 90713019), the National Natural Science Foundation of China (Grant No. 20875057), the Natural Science Foundation of Shandong Province, China (Grant No. Y2007B02), and the Science and Technology Development Programs of Shandong Province, China (Grant No. 2008GG30003012)     

Direct electrochemistry behavior of Cytochrome c on silicon dioxide nanoparticles-modified electrode

A newfangled direct electrochemistry behavior of Cytochrome c (Cyt c) was found on glassy carbon (GC) electrode modified with the silicon dioxide (SiO2) nanoparticles by physical adsorption. A pair of stable and well-defined redox peaks of Cyt c′ quasi-reversible electrochemical reaction were obtained with a heterogeneous electron transfer rate constant of 1.66×10-3 cm/s and a formal potential of 0.069 V (vs. Ag/AgCl) (0.263 V versus NHE) in 0.1 mol/L pH 6.8 PBS. Both the size and the amount of SiO2 nanoparticles could influence the electron transfer between Cyt c and the electrode. Electrostatic interaction which is between the negative nanoparticle surface and positively charged amino acid residues on the Cyt c surface is of importance for the stability and reproducibility toward the direct electron transfer of Cyt c. It is suggested that the modification of SiO2 nanoparticles proposes a novel approach to realize the direct electrochemistry of proteins.     

Quantum dynamics of dissociative adsorption of H2 and D2: The time-dependent wave packet method

A time-dependent quantum wave packet method was used to study the dynamics of dissociative adsorption of H₂ and D₂ on a flat and static surface. The molecule-surface interaction is described using a modified London-Eyring-Polanyi-Sato (LEPS) type potential for the H₂/Ni(100) system. The three-dimensional (3-D) dissociation probabilities were calculated for different initial rovibrational states as a function of initial incident energies. Our results show that the dissociation of the diatomic rotational states whose quantum numbers satisfyj+m = odd is forbidden at low energies for the homonuclear H_z and D₂ due to the selection rule. The effect of the rotational orientation of diatoms on adsorption predicts that the in-plane rotation (m = j) is more favorable for dissociation than the out-of-plane rotation (m = 0). Enhanced dissociation for vibrationally excited molecules and the significant enhancement of the dissociation probability of H2 when compared to D₂ were explained reasonably in terms of quantum mechanical zero-point energies, the tunneling effect and the reflection from an activation barrier. Project supported by the National Natural Science Foundation of China (Grant No. 19694033) and partially by the Science Foundation for Overseas Chinese Scholars and Students, administered by the State Education Commission of China (Grant No. 1992), by the State Key Laboratory of Theoretical and Computational Chemistry of Jilin University at Changchun (Grant No. 98011, and by the Natural Science Foundation of Shandong Province (Grant No. Y96B03022)     

Assembly, crystal structure, and luminescent properties of three-dimensional (10,3)-a netted rare earth coordination polymers

Solid complexes [REL(NO3)3]n with novel (10,3)-a type three-dimensional networks structure have been assembled using rare earth nitrates and an amide type semirigid tripodal bridging ligand, 1,3,5-tris {[(2′-benzylaminoformyl)phenoxyl]methyl}benzene (L), as building blocks. The complexes were crys- tallized in the orthorhombic system with chiral space group P212121. The whole structure consists of an infinite array of trigonal RE(III) ions bridged by tridentate ligands, and a novel (10,3)-a net is formed, which is very uncommon in the rare earth complexes. At room temperature, the Sm(III), Eu(III), Tb(III), Dy(III) complexes all exhibited characteristic luminescence emissions of central metal ions under UV light excitation.     

Resonance scattering spectral detection of ultratrace IgG using immunonanogold-HAuCl<Subscript>4</Subscript>-NH<Subscript>2</Subscript>OH catalytic reaction

Nanogold particles of 10 nm were used to label goat anti-human IgG (GIgG) to obtain nanogold-labeled GIgG (AuGIgG). In a citrate-HCI buffer solution of pH 2.27, AuGIgG showed a strong catalytic effect on the reaction between HAuCl₄ and NH₂OH to form big gold particles that exhibited a resonance scattering (RS) peak at 796 nm. Under the chosen conditions, AuGIgG combined with IgG to form immunocomplex AuGIgG-IgG that can be removed by centrifuging at 16000 r/min. AuGIgG in the centrifuging solution also showed catalytic effect on the reaction. On those grounds, an immunonanogold catalytic RS assay for IgG was designed. With addition of IgG, the amount of AuGIgG in the centrifuging solution decreased; the RS intensity at 796 nm (I _{796 nm}) decreased linearly. The decreased intensity ΔI _{796 nm} was linear with respect to the IgG concentration in the range of 0.08–16.0 ng · mL⁻¹ with a detection limit of 0.02 ng · mL⁻¹. This assay was applied to analysis of IgG in sera with satisfactory sensitivity, selectivity and rapidity. Supported by the National Natural Science Foundation of China (Grant No. 20667001), Natural Science Foundation of Guangxi Province (Grant No. 0728213), and the Foundation of New Century Ten-Hundred-Thousand Talents of Guangxi Province     

An accurate three-dimensional potential energy surface for the He-Na<Subscript>2</Subscript> complex

An accurate three-dimensional potential energy surface (PES) for the He-Na₂ van der Waals complex was calculated at the coupled cluster singles-and-doubles with noniterative inclusion of connected triple (CCSD(T)) level of theory. A mixed basis set, aug-cc-pVQZ for the He atom and cc-pCVQZ for the sodium atom, and an additional (3s3p2d1f) set of midbond functions were used. The computed interaction energies in 819 configurations were fitted to a 96-parameter analytic potential model by least squares fitting. The PES has two shallow wells corresponding to the T-shaped structure and the linear configuration, which are located at 12.5a ₀ and 14 a ₀ with depths of 1.769 and 1.684 cm⁻¹, respectively. The who potential energy surface exhibits weak anisotropy. Based on the fitted PES, state-to-state differential cross sections were calculated. Supported by the Natural Science Foundation of Anhui Educational Committee (Grant No. 2006kj072A) and the Natural Science Foundation of Anhui Province (Grant No. 070416236)     

Planar or quasi-planar octa- and ennea-coordinate aluminum and gallium in boron rings

An ab initio theoretical investigation has been performed on planar or quasi-planar octa-and ennea-coordinate Al and Ga centered in X@B8- and X@B9 (X=Al, Ga). These high symmetry molecular wheels all turned out to be true minima of the systems and σ+π double aromatic in nature, similar to the previously characterized D8h B@B8- both electronically and geometrically. Adiabatic and vertical detachment energies of the anions and the ionization potentials of the neutrals have been calculated to aid their eventua...     

PdCl2-catalyzed heterocyclotrimerization in MeOH/scCO2: A versatile approach to dimethyl pyridine-3,5-dicarboxylate from methyl acrylate and urea

A novel and green method for the synthesis of dimethyl pyridine-3,5-dicarboxylate has been developed. It is PdCl₂-catalyzed heterocyclotrimerization of methyl acrylate with urea in methanol/supercritical carbon dioxide. The target compound was obtained with a 75% isolated yield under the optimized conditions. Supported by the National Natural Science Foundation of China (Grant Nos. 20332030, 20572027, 20625205 and 20772034) and Guangdong Natural Science Foundation (Grant No. 07118070)     

Study on the recovery of hydrogen from refinery (hydrogen + methane) gas mixtures using hydrate technology

A novel technique for separating hydrogen from (H2 CH4) gas mixtures through hydrate formation/dissociation was proposed. In this work, a systematic experimental study was performed on the separation of hydrogen from (H2 CH4) feed mixtures with various hydrogen contents (mole fraction x = 40%-90%). The experimental results showed that the hydrogen content could be enriched to as high as ~94% for various feed mixtures using the proposed hydrate technology under a temperature slightly above 0℃ and a pressure below 5.0 MPa. With the addition of a small amount of suitable additives, the rate of hydrate formation could be increased significantly. Anti-agglomeration was used to disperse hydrate particles into the condensate phase. Instead of preventing hydrate growth (as in the kinetic inhibitor tests), hydrates were allowed to form, but only as small dispersed particles. Anti-agglomeration could keep hydrate particles suspended in a range of condensate types at 1℃ and 5 MPa in the water-in-oil emulsion.     

Potential energy curves for the X1∑ g, B1△g and B''''1∑ g states of C2 using MRCI and approximate CI methods

The potential energy curves for the X1∑ g, B1△g and B′1∑ g states of C2 have been studied by using MRCI and approximate CI methods, and are benchmarked against the calculations of full configuration interaction (FCI). The results obtained by MRCI method agree with the FCI very well, and even are accurate enough to compare other approximate methods as benchmark, when the calculations of FCI are not feasible. The approximate CI methods mentioned in this paper are reliable for treating chemical problems.     

Synthesis and catalytic activity of novel heteronuclear Ln (III) -Cu(II) complexes with noncyclic polyether-amino acid Schiff base

A series of novel heteronuclear Ln(III)-CU(II) complexes with noncyclic polyether-amino acid Schiff base were synthesized. The general formula is (LnCu₂(H₂TALY) (NO₃)₅] (NO₃)₂·nH₂O (Ln= La, Nd, Sm, Gd,n = 4; Ln = Yb, Y,n = 3), where H₂TALY = tetraglycol aldehyde bis-lysine Schiff base. It is the first time to report the synthetic method for this new Cu(II) complexes and Ln(III)-Cu(II) heteronuclear complexes. The complexes were characterized by elemental analysis, IR spectra. TG-DTA, magnetic susceptibility, and especially by a 500 MHz NMR spectrometer for 2D-COSY NMR. Coordination mechanism and structures of complexes have been suggested as well. Of particular interest is the potential that the novel complexes obtained may be used as a catalyst. which prompted us to investigate them. It shows 100% conversion with the viscosity-average molecular weight 120 000 for the polymerization of methyl methacrylate (MMA) without addition of any cocatalyst. Furthermore, the complexes with such aliphatic Schiff bases can be used as a good catalyst, which has been confirmed and discussed here. They may be a new kind of catalyst system with the above speciality. Project supported by the National Natural Science Foundation of China (Grant No. 29671026) and Natural Science Foundation of Zhejiang Province (Grant No. 296062) and the Laboratory of MRAMP (Grant No. 971502).     

New bienzymatic strategy for glucose determination by immobilized-gold nanoparticle-enhanced chemiluminescence

Bienzymatic biosensor for the determination of glucose by flow injection chemiluminescence (CL) detection was proposed. Hybrids of gold nanoparticles (GNPs) and chitosan were chosen as the immobilization matrix of glucose oxidase (GOD) and horseradish peroxidase (HRP) to fabricate the biosensors with silane-pretreated glass microbeads. After the enzyme catalyzing oxidation of glucose in GOD biosensor, the produced H₂O₂ flowed into HRP biosensor to react with luminol. The doped GNPs in chitosan were found to enhance the classical CL reaction of luminol-H₂O₂-HRP. The CL enhancement was investigated in detail by CL and UV-visible spectrum. Under the optimized experimental conditions, glucose could be determined in a linear range from 0.01 to 6.0 mmol/L with a detection limit of 5.0 μmol/L at 3σ. The accuracy of the proposed method was examined by detecting the glucose level in four clinical serum samples from hospital. The proposed method provides a new alternative to determine glucose. Supported by the Natural Science Foundation of Shandong Province (Grant No. Q2007B03), the Doctoral Fund of Qingdao University of Science and Technology (Grant No. 0022141), and the National Natural Science Foundation of China (Grant No. 20775038)     

Preparation and characterization of CoFe2O4/TiO2 magnetic composite films

CoFe₂O₄/TiO₂ magnetic composite films were prepared using the sol-gel method with tetrabutyltitanate and metallic chlorates as starting materials. The effects of heat treatment temperatures on microstructures and on magnetic properties were studied. The microstructure and properties of the samples at different heat treatment temperatures were characterized by X-ray diffraction, Raman spectrum, scanning electron microscopy, polarized microscopy and vibrating sample magnetometry. The results show that crystals of different substances grow up independently. Cobalt ferrite is evenly embedded into the titanium dioxide matrix in the prepared composite films. The magnetism of the composite films is enhanced with an increase of the heat temperature. Supported by the National Natural Science Foundation of China (Grant Nos. 50632030 and 10474077), and the Natural Science Foundation of Shaanxi Province (Grant No. 2006E135)     

Crystal structures and electronic properties of BaC<Subscript>2</Subscript> isomers by theoretical study based on DFT

Band structures and electronic properties of two BaC₂ isomers were calculated by using density functional theory (DFT) properly. The ionic bond features are all typical between cation (Ba) and anion clusters (C₂) in both structures of the isomers. However, a much stronger covalent bond exists in anion clusters which can be seen by inspecting the electron distribution contour that has a dull bell like shape between two carbon atoms. The shortest distance between Ba²⁺ and C₂²⁻ and the bond length in anion clusters are different in these isomers of BaC₂, which are 0.2945 nm and 0.1185 nm for the structure with the I4/mmm space group and 0.2744 and 0.1136 nm with the C2/c type, respectively. Band structures were clarified by combining the DOS to indicate the ionic bonding features more clearly. Population analysis provided further evidence on these ideas. Thermodynamical calculation results reveal that the transition temperature of these two polymorphs of BaC₂ locates near 132 K, which is consistent with the recent experimental results. Supported by the National Natural Science Foundation of China (Grant No. 50361003) and the Natural Science Foundation of Yunnan Province (Grant No. 2006003Z) and Science Innovation Foundation of Kunming University of Science and Technology     

3D-QSAR and docking studies of estrogen compounds based on estrogen receptor β

Close attention has been paid to estrogen compounds because these chemicals may pose a serious threat to the health of humans and wildlife. Estrogen receptor (ER) exists as two subtypes, ERα and ERβ. The difference in amino acids sequence of the binding sites of ERα and ERβ might lead to a result that some synthetic estrogens and naturally occurring steroidal ligands have different relative affinities and binding modes for ERα and ERβ. In this investigation, comparative molecular similarity indices analysis...     

The enzyme-amplified amperometric DNA sensor using an electrodeposited polymer redox mediator

A highly sensitive method for the detection of a breast cancer-associated BRCA-1 gene is reported. The detection is based on a classical sandwich-type assay using horseradish peroxidase (HRP) as a catalytic label and electrodeposited Os^2+/3+ conducting polymer (PAA-PVI-Os) as a redox mediator. Target DNA could be detected by the HRP-catalyzed reduction of H₂O₂, leading to a limit of detection as low as 10 fM. Supported by the National Natural Science Foundation of China (Grant Nos. 20725516, 20704043, 20873175 & 20805055), Shanghai Municipal Commission for Science and Technology (Grant Nos. 0752nm021 & 07ZR14136), Ministry of Science and Technology (Grant Nos. 2006CB933000, 2007CB936000 & 2007AA06A406), Ministry of Health (Grant No. 2009ZX10603), and China Postdoctoral Science Foundation and Shanghai Postdoctoral Scientific Program (Grant No. 07R214160).     

Resonance-enhanced photon excitation spectroscopy of the even-parity autoionizing Rydberg states of Kr

Kr atoms were produced in their metastable states 4p⁵5s [3/2]₂ and 4p⁵5s’ [1/2]₀ in a pulsed DC discharge in a beam, and subsequently excited to the even-parity autoionizing Rydberg states 4p⁵ np′ [3/2]_1,2, [1/2]₁ and 4p⁵ nf′ [5/2]₃ using single photon excitation. The excitation spectra of the even-parity autoionizing resonance series from the metastable Kr were obtained by recording the autoionized Kr⁺ ions with time-of-flight ion detection in the photon energy range of 29000–40000 cm⁻¹. A wealth of autoionizing resonances were newly observed, from which more precise and more systematic spectroscopic data of the level energy and quantum defects were derived. Supported by the National Natural Science Foundation of China (Grant No. 20673107), the National Key Basic Research Special Foundation of China (Grant No. 2007CB815203), and Chinese Academy of Sciences (Grant No. KJCX2-SW-H08)     

In-situ UV-Raman study on soot combustion over TiO2 or ZrO2-supported vanadium oxide catalysts

UV-Raman spectroscopy was used to study the molecular structures of TiO₂ or ZrO₂-supported vanadium oxide catalysts. The real time reaction status of soot combustion over these catalysts was detected by in-situ UV-Raman spectroscopy. The results indicate that TiO₂ undergoes a crystalline phase transformation from anatase to rutile phase with the increasing of reaction temperature. However, no obvious phase transformation process is observed for ZrO₂ support. The structures of supported vanadium oxides also depend on the V loading. The vanadium oxide species supported on TiO₂ or ZrO₂ attain monolayer saturation when V loading is equal to 4 (4 is the number of V atoms per 100 support metal ions). Interestingly, this loading ratio (V₄/TiO₂ and V₄/ZrO₂) gave the best catalytic activities for soot combustion reaction on both supports (TiO₂ and ZrO₂). The formation of surface oxygen complexes (SOC) is verified by in-situ UV Raman spectroscopy and the SOC mainly exist as carboxyl groups during soot combustion. The presence of NO in the reaction gas stream can promote the production of SOC. Supported by the National Natural Science Foundation of China (Grant Nos. 20473053, 20773163 and 20525621), the Beijing Natural Science Foundation (Grant No. 2062020), and the 863 Program of China (Grant No. 2006AA06Z346)