-
[show abstract]
[hide abstract]
ABSTRACT: The title compound is an "off-on" rhodamine probe. It exhibits strong pH dependence and responds to protons. The optimized geometries and energies calculation of the protonation were determined at the B3LYP level using DFT. The theoretical results are in good agreement with the single crystal analysis and the spectral results.
Organic & Biomolecular Chemistry 08/2012; 10(38):7677-80. · 3.70 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The highly efficient and selective production of 5-hydroxymethylfurfural (HMF) from sucrose has been achieved in the presence of metal chlorides and ammonium halides under mild conditions. Notably, an 87% yield of HMF from sucrose was obtained with a catalyst system composed of CrCl(3) and NH(4)Br at 100°C for 1.0 h in N,N-dimethylacetamide (DMAc) solvent. The effect of the reaction temperature and time was investigated in detail, and a possible mechanism for this catalytic process has been proposed. In addition, NH(4)Br is an effective promoter in the conversion of glucose and fructose to HMF.
Carbohydrate research 11/2011; 347(1):182-5. · 2.03 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Potential energy surfaces of the imine-ene reaction between methanimine and propene have been calculated using restricted and unrestricted density functional theory at the B3LYP level. The results show that a concerted mechanism with an exo configuration for lone pair electrons transition structure is more favourable for the intermolecular bare imine-ene reaction. In addition, the C-C bond formation and the migration of the propene α-hydrogen occur simultaneously. The promoting effect of seventeen Lewis acids was also studied. When a Lewis acid is used as a promoter, the corresponding activation and reaction energies decline greatly compared to those of the bare imine-ene reaction. A good correlation (R(2) > 0.9) was found between the activation barriers and the polar character of the transition states. Lewis acids and electron-withdrawing substituents on methanimine were proven to facilitate the imine-ene reaction, whereas electron-donating groups, conjugated groups or a bulky group hinders the reaction. The steric factor is the most unfavourable. The reactivity indices defined by the conceptual density functional theory were also studied and there is a good correlation between the activation barrier and electrophilicity. Frontier molecular orbital theory gives a good explanation for the above results.
Organic & Biomolecular Chemistry 07/2011; 9(18):6343-51. · 3.70 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A new wearable colorimetric fiber for heavy metal ion detection and adsorption has been synthesized by first aminating a commercially available polyacrylonitrile fiber with ethylenediamine and then covalently immobilizing 4-(2-pyridylazo)-1,3-benzenediol (PAR) on the modified fiber through a Mannich reaction. The fiber was characterized by X-ray powder diffraction spectra (XRD), scanning electron microscope (SEM), FTIR and UV-vis spectroscopy, and its acid exchange capacity, colorimetric properties, response speed, selectivity, reusability, photostability and adsorption capacity were investigated. In neutral aqueous solutions, the PAR immobilized fiber responds selectively to heavy metal ions, such as Hg(2+), Pb(2+), Cd(2+), Zn(2+), Ni(2+) and Cu(2+) with a color change from red-orange to dark-brown. Its visual detection limit for Pb(2+) is 1 x 10(-6)mol/L. Moreover, the selectivity increases with a decrease in pH, i.e. at pH 3.0, it shows a color change only for Hg(2+) and Cu(2+). This fiber also shows excellent reusability (>50 times), high photostability (>30 days under direct exposure to sunlight) and high adsorption capacity for Hg(2+) (0.74 mmol/g).
Journal of hazardous materials 05/2010; 177(1-3):983-9. · 4.14 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Theoretical studies of the stereodynamics for the chemical reaction H + LiH+(v = 0, j = 0) → Li++ H2 were conducted using the quasi-classical trajectory (QCT) method on the three-dimensional potential energy surface [J. Chem. Phys. 119, 11241 (2003)] at three collision energies (0.01, 0.05 and 0.1 eV). The calculated DCS results indicate that the products tend to both extreme forward and backward scattering. Because the potential well lying in the product valley is a weak van der Waals well, the forward–backward scattering is asymmetric. The calculated P(θr ) shows that the rotational angular momentum polarization of the product molecule is quite strong and insensitive to increasing collision energy. For the title reaction, it is not a deep well but a shallow Van der Waals well about 0.286 eV below the Li++ H2 asymptote on the PES. Hence, the reaction mainly behaves as an exoergic reaction rather than an insertion mechanism. The distributions of indicate that j′ is not only aligned, but also oriented preferentially along the positive direction of the y-axis. The distributions indicate that the product molecules are preferentially polarized perpendicular to the scattering plane and that the reaction is dominated by an in-plane mechanism.
Molecular Physics 12/2009; 107(Nos. 23-24):2579-2585. · 1.82 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Theoretical studies of the dynamics of the abstraction reaction, H' + HBr (v=0,j=0) --> H'H + Br, have been performed with quasiclassical trajectory method (QCT) on a new ab initio potential energy surface (Y. Kurosaki and T. Takayanagi, private communication). The calculated QCT cross sections are in good agreement with earlier quantum wave packet results over most of the collision energy range from 0.1 to 2.6 eV, and the state-resolved rotational distributions of the product H'H molecule are quantitatively consistent with the experimental results. Comparisons of the QCT-calculated rotational-state-resolved cross sections on different potential energy surfaces show that the characteristics of the potential energy surface in the region far away from the minimum energy path have a large influence on the title abstraction reaction dynamics, and the indirect reactions that do not follow the minimum energy path have little influence on the differential cross sections (DCS). The DCSs are mainly governed by the direct reactions that do follow the minimum energy path, at both low and high collision energies. The degree of the rotational alignment of the product H'H molecule is strong at high collision energies, which means that the influence of the indirect reactions on the product rotational alignment is negligible, whereas the distribution of P(varphi(r)) is sensitive to the indirect reactions at high collision energies. With increasing collision energy, the polarization of the product rotational angular momentum decreases and the molecular rotation of the product prefers an in-plane reaction mechanism rather than the out-of-plane mechanism.
The Journal of Physical Chemistry A 03/2009; 113(16):4192-7. · 2.95 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Molybdenum clusters consisting of 2-55 atoms were investigated using density functional theory calculations with a plane-wave basis set. The results show that the linear and planar molybdenum clusters have a strong tendency to form dimers. This tendency results in the formation of alternate short and long bonds within a linear cluster, in which the strength of these short bonds is covalent. Therefore, the linear and planar Mo clusters exhibit significant nonmetallic characteristics. Furthermore, the linear and planar Mo clusters show a strong even-odd effect in binding energy with the even-numbered clusters being more stable than their neighboring odd-numbered clusters. On the other hand, the even-odd effect in the energy gap between the highest occupied and the lowest unoccupied molecular orbitals, i.e., the HOMO-LUMO energy gap, for the linear and the planar clusters is different. The odd-numbered linear clusters and even-numbered planar clusters have larger HOMO-LUMO energy gaps than their corresponding neighboring clusters.
The Journal of Chemical Physics 11/2004; 121(16):7717-24. · 3.33 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Ruthenium clusters of up to 64 atoms were studied using density-functional theory with a plane wave basis set. The simple cubic structure was found to be the most stable structure in the formation of small ruthenium clusters. A strong trend of trimer formation was also observed in the linear ruthenium clusters. All the ruthenium clusters investigated in this work are ferromagnetic with large magnetic moments and have small energy gaps between the highest occupied and the lowest unoccupied molecular orbitals. A quantitative correlation was established between the energetic, electronic, and magnetic properties of ruthenium clusters and the cluster size and structure. Our analysis showed that the atoms in similar bonding environments have similar binding energies. On the basis of this analysis, estimations were made on the binding energy for certain planar and simple cubic ruthenium clusters. The estimated binding energies are in good agreement with those from the density-functional theory calculations.
01/2004;
-
[show abstract]
[hide abstract]
ABSTRACT: Two novel tweezer-like 25,27-dihydroxy-26,28-bis(phenylthiaethoxy)calix[4]arenes 6 and 7 were synthesized by the reaction of 25,27-dihydroxy-26,28-bis(bromoethoxy)calix[4]arenes 3 and 4 for the evaluation of their ion-selectivity in ion-selective electrodes (ISEs). X-ray structural analysis indicated that calix[4]arene 7 is in an interesting infinite linear aggregate via self-inclusion. For investigation of the influences of substitutes on the behavior of the ISEs, the halogen substituted aryl analogues of 25,27-dihydroxy-26,28-bis(arylthiaethoxy)calix[4]arenes 8-12 were also synthesized and their ISE performances were evaluated under the same conditions. ISEs based on 6-12 as neutral ionophores were prepared, and their selectivity coefficients for Ag+ (log KAg,M(pot)) were investigated against other alkali metal, alkaline-earth metal, lead, ammonium ions and some transition metal ions using the fixed interference method (FIM). These ISEs showed excellent Ag+ selectivity over most of the interfering cations examined, except for Hg2+ having relative smaller interference (log KAg,Hg(pot) < or = 2.1). The 19F NMR spectra of 9 and 9.AgClO4 were recorded for investigation the fluorine environments in the complex. The 19F NMR spectra strongly suggested that the fluorine atoms on ionophore 9 participated in ligation with silver cation.
Organic & Biomolecular Chemistry 03/2003; 1(6):1073-9. · 3.70 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A reusable chelating fiber containing polyamino–polycarboxylic acid ligands was prepared via the stepwise modification of polyacrylonitrile fiber with diethylenetriamine and chloroacetic acid. The amination and carboxylmethylation conditions were optimized, and the modified fiber was characterized by elemental analysis, XRD, SEM and FTIR. For Cd2+ in water, this chelating fiber has prominent adsorption abilities such as low adsorption limitation (0.001 mg/L), high adsorption capacity (1.34 mmol/g) and fast response speed (half-saturation adsorption time less than 0.5 min based on 1 mg/mL Cd2+). The effectiveness of this chelating fiber has been proved by using it to treat actual sewage water, where the concentration of Cd2+ was reduced from 0.540 to below 0.001 mg/L. This level easily meets drinking water standards (0.003 mg/L) issued by the World Health Organization. Moreover, this chelating fiber is also very effective at treating other metal ions such as Cu2+, Ca2+, Zn2+, Mg2+, Pb2+, Ni2+, Ag+ and Hg2+.
Reactive and Functional Polymers 69(1):48-54. · 2.48 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A series of N-heteroaryl-1,8-naphthalimides with good sensitivity to solvent polarity were prepared. Empirical and quantum calculations showed that the electron withdrawing effect of the heteroaryl group increases the change in dipole moment on excitation which results in the fluorescence quantum yield dramatically falling as the solvent polarity increases. A typical compound 4-(1-piperidyl)-N-(2-pyrimidinyl)-1,8-naphthalimide was chosen to determine the water content in six common solvents (p-dioxane, tetrahydrofuran, acetone, dimethylformamide, acetonitrile and methanol). Fluorescence intensity changes as a function of water content correlated well with a modified Stern–Volmer equation over a wide range, with detection limits being 0.016% and 0.020% for acetone and tetrahydrofuran, respectively.
Dyes and Pigments 88(3):307-314. · 3.13 Impact Factor
-
Journal of Molecular Structure. 1026:133-139.
