摘要：
Nanometer titanium dioxide immobilized on silica gel (immobilized nanometer TiO(2)) was prepared by sol-gel method and characterized by using X-ray diffraction (XRD) and scanning electron microscope (SEM). The adsorptive potential of immobilized nanometer TiO(2) for the preconcentration of trace Cd, Cr, Cu and Mn was assessed in this work. The metal ions studied can be quantitative retained at a pH range of 8-9, and 0.5molL(-1) HNO(3) was sufficient for complete elution. The adsorption capacity of immobilized nanometer TiO(2) for Cd, Cr, Cu and Mn was found to be 2.93, 2.11, 6.69 and 2.47mgg(-1), respectively. A new method using a microcolumn packed with immobilized nanometer TiO(2) as sorbent has been developed for the preconcentration of trace amounts of Cd, Cr, Cu and Mn prior to their determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). The method has been successfully applied for the determination of trace elements in some environmental samples with satisfactory results.
期刊：
JOURNAL OF ORGANIC CHEMISTRY,2004年69(19):6157-6164 ISSN：0022-3263
通讯作者：
Isaacs, L
作者机构：
[Isaacs, L] Univ Maryland, Dept Chem & Biochem, College Pk, MD 20742 USA.;Cent China Normal Univ, Coll Chem, Hubei 430079, Peoples R China.
通讯机构：
[Isaacs, L] U;Univ Maryland, Dept Chem & Biochem, College Pk, MD 20742 USA.
摘要：
Self-sorting-the ability to efficiently distinguish between self and nonself-is common in nature but is still relatively rare in synthetic supramolecular systems. We report a 12-component mixture comprising 1-11 and KCl that undergoes thermodynamically controlled self-sorting in aqueous solution based on metal-ligand, ion-dipole, electrostatic, charge-transfer interactions, as well as the hydrophobic effect. We refer to this molecular ensemble-characterized by high-fidelity host-guest interactions between components-as a social self-sorting system to distinguish it from narcissistic self-sorting systems based on self-association processes. The influence of several key variables-temperature, pH, concentration, and host/guest stoichiometry-was explored by a combination of simulation and experiment. Variable temperature NMR experiments, for example, revealed a kinetically controlled irreversible process upon cycling from 298 to 338 K, which is an emergent property of this molecular ensemble. Variable pH and concentration experiments, in contrast, did not reveal any emergent properties of the molecular ensemble. Simulations of a four-component mixture establish that by proper control of the relative magnitude of the various equilibrium constants, it is possible to prepare socially self-sorted mixtures that are responsive (irresponsive) to host/guest stoichiometry over narrow (broad) ranges. The 12-component mixture is relatively irresponsive to host/guest stoichiometry. Such social self-sorting systems, like their natural counterparts, have potential applications as chemical sensors, as artificial regulatory elements, and in the preparation of biomimetic systems.
期刊：
Molecular Crystals and Liquid Crystals,2004年420(1):73-77 ISSN：1542-1406
通讯作者：
Liu, SH
作者机构：
[Liu, SH] Cent China Normal Univ, Coll Chem, Wuhan 430079, Peoples R China.
通讯机构：
[Liu, SH] C;Cent China Normal Univ, Coll Chem, Wuhan 430079, Peoples R China.
关键词：
spirobenzopyran;macrocyclic dioxopolyamine;selective coloration;transition metal cations
摘要：
Three new spirobenzopyrans bearing macrocyclic dioxopolyamine were synthesized. Sensitive and selective coloration of the spirobenzopyrans for transition metal cations were observed.
作者机构：
[Lu, GH] Cent China Normal Univ, Coll Chem, Wuhan 430079, Peoples R China.;Wenzhou Med Coll, Sch Pharm, Wenzhou 325027, Peoples R China.;Chaohu Coll, Chaohu 238000, Peoples R China.
通讯机构：
[Lu, GH] C;Cent China Normal Univ, Coll Chem, Wuhan 430079, Peoples R China.
摘要：
In the buffer solution of NH3-NH4Cl (pH = 8.5, 0.04 mol l-1), iron-Methylthymol Blue (MTB) can produce a sensitive polarographic wave at -1.10 V (vs. SCE) in the NaNO2. The peak current is linear with the concentration of the iron in the range of 3 × 10-8-5 × 10-6 mol l-1, and the detection limit is 1 × 10-8 mol l-1. By studying the characteristics of the wave and the electrode reaction mechanism, we can prove that the catalytic wave is an adsorption wave and that the peak current comes from the reduction of Fe(II). The molar ratio of iron to ligand was found to be 1:1. Adsorption particles are neutral molecules, the saturated adsorption quantity of the complex on the mercury electrode is 1.92 × 10-9 mol cm-2, according with the Frumkin isothermal formula. In the experiments, the adsorption coefficient (β) is 4.05 × 105; the adsorption factor (γ) is 0.70; the electron transfer number (n) is 2; the free energy (ΔG°) is 31.99 kJ mol-1; the transfer coefficient of the irreversible adsorption is 0.42-0.45; and the reaction velocity constant (Ks) is 1.35 s-1. This method, whose result is satisfying, can be applied to the detection of trace total iron contents in medicinal products.
期刊：
JOURNAL OF PHYSICAL CHEMISTRY A,2004年108(30):6407-6413 ISSN：1089-5639
通讯作者：
Zhan, CG
作者机构：
[Zhan, CG] Cent China Normal Univ, Coll Chem, Wuhan 430079, Peoples R China.;Univ Kentucky, Coll Pharm, Dept Pharmaceut Sci, Lexington, KY 40536 USA.
通讯机构：
[Zhan, CG] C;Cent China Normal Univ, Coll Chem, Wuhan 430079, Peoples R China.
摘要：
The activation free energies for alkaline hydrolysis of cyclic and acyclic phosphodiesters in aqueous solution were investigated using the first principles electronic structure calculations. For all the phosphodiesters followed a one-step bimolecular mechanism initiated by the attack of hydroxide ion at the phosphorus atom of the ester. It was observed that the hydroxide ion-catalyzed hydrolysis involved a pentacoordinated phosphorus intermediate for all examined compounds, except paraoxon. Results show that solvent effects decreases the activation free energies for the alkaline hydrolysis of phosphodiesters.
摘要：
The carbodiimides 4, obtained from aza-Wittig reactions of iminophosphorane 3 with aromatic isocyanates, reacted with secondary amines to give 2-dialkylamino-5,6,7,8-tetrahydro-benzothieno[2,3-d]pyrimidin-4(3H)-ones 6 in presence of catalytic EtO-Na+. Reactions of 4 with phenols or ROH in presence of catalytic K2CO3 or RO -Na+ gave 2-aryl(alkyl)oxy-5,6,7,8-tetrahydro- benzothieno[2,3-d]pyrimidin-4(3H)-ones 6 in satisfactory yields. The effects of the nucleophiles on cyclization have been investigated.
期刊：
Molecular Crystals and Liquid Crystals,2004年419(1):97-101 ISSN：1542-1406
通讯作者：
Liu, SH
作者机构：
[Liu, SH] Cent China Normal Univ, Coll Chem, Wuhan 430079, Peoples R China.
通讯机构：
[Liu, SH] C;Cent China Normal Univ, Coll Chem, Wuhan 430079, Peoples R China.
关键词：
macrocyclic dioxopolyamine;selective coloration;spirobenzopyran;transition metal cations
摘要：
Three new spirobenzopyrans bearing a macrocyclic dioxipolyamine were synthesized. Sensitive and selective coloration of the spirobenzopyrans for transition metal cations were observed.
作者机构：
[Lu, GH] Cent China Normal Univ, Coll Chem, Wuhan 430079, Peoples R China.;Caohu Coll, Dept Chem, Anhui 238000, Peoples R China.
通讯机构：
[Lu, GH] C;Cent China Normal Univ, Coll Chem, Wuhan 430079, Peoples R China.
摘要：
A chemically modified electrode based on a chitosan-multiwall carbon nanotube (MWNT) coated glassy carbon electrode (GCE) is described, which exhibits an attractive ability to determine dopamine (DA) and ascorbic acid (AA) simultaneously. The modified electrode exhibited a high differential pulse voltammetry (DPV) current response to DA at 0.144 V and AA at -0.029 V (vs. SCE) in a 0.1 mol l-1 phosphate buffer solution (pH = 7.2). The properties and behaviors of the chitosan-multiwall carbon nanotube modified electrode (MC/GCE) were characterized using cyclic voltammetry (CV) and DPV methods. The mechanism for the discrimination of dopamine from ascorbic acid at MC/GCE is discussed. The linear calibration range for DA and AA were 5 × 10-7 mol l-1 to 1 × 10-4 mol l -1 (r = 0.997), and 5 × 10-6 mol l-1 to 1 × 10-3 mol l-1 (r = 0.996), respectively. The MC/GCE showed good sensitivity, selectivity and stability.
期刊：
JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY,2004年19(8):1006-1009 ISSN：0267-9477
通讯作者：
Liang, P
作者机构：
[Liu, Y; Liang, P; Guo, L] Cent China Normal Univ, Coll Chem, Wuhan 430079, Peoples R China.
通讯机构：
[Liang, P] C;Cent China Normal Univ, Coll Chem, Wuhan 430079, Peoples R China.
摘要：
A sensitive and selective method has been developed for the determination of Mo in steel samples using a nanometre-sized titanium dioxide micro-column (20 mm × 3.0 mm id) and inductively coupled plasma atomic emission spectrometry (ICP-AES). Under the optimized conditions (pH 1.0, flow rate 1.5 mL min−1), Mo was retained on the column and separated from the iron matrix, then eluted with 0.5 mol L−1 NaOH and determined by ICP-AES. The adsorption capacity of nanometre TiO2 for Mo was found to be 2.01 mg g−1. The detection limit for Mo was 0.14 μg L−1, with an enrichment factor of 100, and the relative standard deviation (RSD) was 1.8% (n = 11, C = 50 μg L−1). The proposed method has been applied to the determination of Mo in certified reference steel samples with satisfactory results.
期刊：
JOURNAL OF ORGANIC CHEMISTRY,2004年69(24):8366-8371 ISSN：0022-3263
通讯作者：
Ding, MW
作者机构：
[Zhao, JF; Xu, SZ; Ding, MW] Cent China Normal Univ, Coll Chem, Key Lab Pesticide & Chem Biol, Minist Educ, Wuhan 430079, Peoples R China.
通讯机构：
[Ding, MW] C;Cent China Normal Univ, Coll Chem, Key Lab Pesticide & Chem Biol, Minist Educ, Wuhan 430079, Peoples R China.
摘要：
The bis(carbodiimides) 4, obtained from bis-aza-Wittig reactions of bis(iminophosphorane) 3 with 2 equiv of aromatic isocyanates, were reacted with secondary amine to give symmetrically substituted 2,7-diaminothieno[2,3-d:5,4-d']dipyrimidine-4,5(3H,6H)-dione 6 in the presence of a catalytic amount of EtO(-)Na(+). Reactions of 4 with phenols or ROH in the presence of a catalytic amount of potassium carbonate or RO(-)Na(+) gave symmetrically substituted 2,7-diaryl(alkyl)oxythieno[2,3-d:5,4-d']dipyrimidine-4,5(3H,6H)-diones 6 in satisfactory yields. However, iminophosphoranes 9 were obtained via reaction of bis(iminophosphorane) 3 with 1 equiv of aromatic isocyanate and subsequent reaction with an amine in the presence of a catalytic amount of EtO(-)Na(+). Further reaction of iminophosphoranes 9 with aromatic isocyanates and various nucleophile generated unsymmetrically substituted thieno[2,3-d:5,4-d']dipyrimidine-4,5(3H,6H)-diones 12 in good yields.
作者机构：
[Liu, L] Cent China Normal Univ, Coll Chem, Wuhan 430079, Peoples R China.;Cent China Normal Univ, Nano Sci & Technol Res Ctr, Wuhan 430079, Peoples R China.
通讯机构：
[Liu, L] C;Cent China Normal Univ, Coll Chem, Wuhan 430079, Peoples R China.
关键词：
Diffuse reflectance UV-Vis spectroscopy;Electrochemical method;High resolution transmission electron microscopy;Nano-size TiO 2 -Cu 2 O particle composites;X-ray photoelectron spectroscopy
期刊：
JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY,2004年19(11):1489-1492 ISSN：0267-9477
通讯作者：
Liang, P
作者机构：
[Liu, Y; Lu, HB; Liang, P; Zeng, J; Guo, L] Cent China Normal Univ, Coll Chem, Wuhan 430079, Peoples R China.
通讯机构：
[Liang, P] C;Cent China Normal Univ, Coll Chem, Wuhan 430079, Peoples R China.
摘要：
The potential of multiwalled carbon nanotubes (MWNTs) as a solid-phase extraction adsorbent for the preconcentration of trace Cd, Mn and Ni has been investigated. The studied metal ions can be adsorbed quantitatively on MWNTs at pH 8.0, then eluted completely with 0.5 mol L<sup>-1</sup> HNO<inf>3</inf>. The adsorption capacity of MWNTs was found to be 7.42, 4.86 and 6.89 mg g <sup>-1</sup> for Cd, Mn and Ni, respectively. A new method using a microcolumn packed with MWNTs as sorbent has been developed for the preconcentration of trace amounts of Cd, Mn and Ni prior to their determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). Parameters influencing the preconcentration of the analytes, such as pH of the sample, sample flow rate and volume, elution solution and interfering ions, have been examined. The method has been successfully applied to the determination of trace elements in some environmental samples with satisfactory results.
期刊：
Solid State Communications,2004年132(2):79-82 ISSN：0038-1098
通讯作者：
Zhu, LP
作者机构：
[Zhu, LP] Cent China Normal Univ, Dept Phys, Ctr Nanosci & Technol, Wuhan 430079, Peoples R China.;Cent China Normal Univ, Coll Chem, Wuhan 430079, Peoples R China.
通讯机构：
[Zhu, LP] C;Cent China Normal Univ, Dept Phys, Ctr Nanosci & Technol, Wuhan 430079, Peoples R China.
关键词：
A. Nanostructures;A. Semiconductors;B. Chemical synthesis
期刊：
JOURNAL OF PHYSICAL CHEMISTRY A,2004年108(17):3789-3797 ISSN：1089-5639
通讯作者：
Zhan, CG
作者机构：
[Zhan, CG] Cent China Normal Univ, Coll Chem, Wuhan 430079, Peoples R China.;Univ Kentucky, Coll Pharm, Dept Pharmaceut Sci, Lexington, KY 40536 USA.
通讯机构：
[Zhan, CG] C;Cent China Normal Univ, Coll Chem, Wuhan 430079, Peoples R China.
摘要：
We have performed a series of first-principles electronic structure calculations to study competing reaction pathways and the corresponding free-energy barriers for the ester hydrolysis of intracellular second-messenger adenosine 3′,5′-cyclic monophosphate (cAMP) and related phosphodiesters including trimethylene phosphate (TMP). Reaction coordinate calculations show three fundamental reaction pathways for the ester hydrolysis, including (A) attack of a hydroxide ion at the P atom of the phosphate anion (an S<inf>N</inf>2 process without a pentacoordinated phosphorus intermediate), (B) direct attack of a water molecule at the P atom of the anion (a three-step process), and (C) direct attack of a water molecule at the P atom of the neutral ester molecule (a two-step process). The calculated energy results show that for the reactions in the gas phase the free-energy barrier for pathway A is the highest and the barrier for the rate-controlling step of pathway C is the lowest. However, for the reactions in aqueous solution, the free-energy barrier calculated for pathway A becomes the lowest, and the two main hydrolysis pathways are A and B. We also have demonstrated how the pK<inf>a</inf> of the ester and the pH of the reaction solution affect the relative contributions of different hydrolysis pathways to the total hydrolysis rate. Reaction pathway A should be dominant for the cAMP hydrolysis in neutral aqueous solution. However, the relative contribution of pathway A to the total hydrolysis rate should decrease with decreasing pH of the solution. For pH <∼3.7, the contribution of pathway B is larger. For pH >∼3.7, the contribution of pathway A is larger. The reliability of our theoretical predictions is supported by the excellent agreement of the calculated free-energy barrier with available experimental data for the hydrolysis of TMP in solution.
摘要：
A new method using nanoparticle TiO<inf>2</inf> as solid-phase extractant coupled with FAAS was proposed for preconcentration and determination of trace Zn and Cd. The effects of pH, contact time, elution solution and interfering ions on the adsorption behavior of nanometer TiO<inf>2</inf> towards Zn and Cd were investigated. Under optimum conditions, nanometer TiO<inf>2</inf> possesses a significant capacity for the sorption of the metal ions studied. The limits of detection (3δ) of this method were 1.8 ng mL<sup>-1</sup> of Zn and 3.0 ng mL<sup>-1</sup> of Cd with an enrichment factor of 12.5, and relative standard deviations were 3.8% and 4.3% for Zn and Cd, respectively (c = 0.5 μg mL<sup>-1</sup>, n = 9). The proposed method was validated by the analysis of water certified reference material.
期刊：
JOURNAL OF PHYSICAL CHEMISTRY A,2004年108(43):9453-9460 ISSN：1089-5639
通讯作者：
Wan, J
作者机构：
[Wan, J] Cent China Normal Univ, Coll Chem, Key Lab Pesticide & Chem Biol, Wuhan 430079, Peoples R China.;Xiamen Univ, Ctr Theoret Chem, Dept Chem, State Key Lab Phys Chem Solid Surfaces, Xiamen 361005, Peoples R China.
通讯机构：
[Wan, J] C;Cent China Normal Univ, Coll Chem, Key Lab Pesticide & Chem Biol, Wuhan 430079, Peoples R China.
摘要：
The electronic ground state and the singlet vertical excited states of tetraoxaporphyrin dication (TOPDC) and porphycene have been investigated by using time-dependent density functional theory (TDDFT) for the first time. The solvation effects on the excitation energies for TOPDC in 96% H2SO4 and porphycene in 2-methyltetrahydrofuran are taken into account by using the polarized continuum model (PCM). The TDDFT-PCM computed results show an obvious red shift of the excitation energies of the B (Soret) bands, leading to a much better agreement with the UV/vis absorption spectra in solutions than the previous semiempirical calculations in vacuo.
期刊：
Journal of Computational Chemistry,2004年25(15):1827-1832 ISSN：0192-8651
通讯作者：
Wan, J
作者机构：
[Zhang, L; Wan, J; Yang, GF] Cent China Normal Univ, Coll Chem, Minist Educ, CCNU, Wuhan 430079, Peoples R China.
通讯机构：
[Wan, J] C;Cent China Normal Univ, Coll Chem, Minist Educ, CCNU, Wuhan 430079, Peoples R China.
关键词：
density functional theory;quantitative structure-activity relationships;inhibitors
摘要：
The equilibrium geometries, electronic structures, and electrostatic potentials of a series of substituted phenyl triazolinones of protoporphyrinogen oxidase (PPO) inhibitors have been investigated by using the density functional theory (DFT) method. The quantum chemical descriptors, highest occupied molecular orbital and lowest unoccupied molecular orbital energy gap (DeltaE), weighted electrophilic, and nucleophilic atomic frontier electron density (FAE and FAN), and net atomic charge (QA), were computed at the same DFT level. Based on these precise quantum chemical descriptors, a quantitative structure-activity relationships study has been carried out and shown that QC11, FN5E, FC10N, and DeltaE of individual molecules are most likely to be responsible for the in vitro biological activity and greenhouse preemergence activity of phenyl triazolinones. The ability to quite accurately predict the biological activity of phenyl triazolinones by using DFT-based QSAR can be expected to help facilitate the design of additional substituted phenyl triazolinones as PPO inhibitors with good biological activity.
