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131.
Ab Initio and DFT Studies on CO2 Interacting with Znq+–Imidazole (q=0, 1, 2) Complexes: Prediction of Charge Transfer through σ‐ or π‐Type Models 下载免费PDF全文
Reda Boulmene Karim Boussouf Dr. Muthuramalingam Prakash Prof. Najia Komiha Dr. Muneerah M. Al‐Mogren Prof. Majdi Hochlaf 《Chemphyschem》2016,17(7):994-1005
Using first‐principles methodologies, the equilibrium structures and the relative stability of CO2@[Znq+Im] (where q=0, 1, 2; Im=imidazole) complexes are studied to understand the nature of the interactions between the CO2 and Znq+–imidazole entities. These complexes are considered as prototype models mimicking the interactions of CO2 with these subunits of zeolitic imidazolate frameworks or Zn enzymes. These computations are performed using both ab initio calculations and density functional theory. Dispersion effects accounting for long‐range interactions are considered. Solvent (water) effects were also considered using a polarizable continuum model approach. Natural bond orbital, charge, frontier orbital and vibrational analyses clearly reveal the occurrence of charge transfer through covalent and noncovalent interactions. Moreover, it is found that CO2 can adsorb through more favorable π‐type stacking as well as σ‐type hydrogen‐bonding interactions. The inter‐monomer interaction potentials show a significant anisotropy that might induce CO2 orientation and site‐selectivity effects in porous materials and in active sites of Zn enzymes. Hence, this study provides valuable information about how CO2 adsorption takes place at the microscopic level within zeolitic imidazolate frameworks and biomolecules. These findings might help in understanding the role of such complexes in chemistry, biology and material science for further development of new materials and industrial applications. 相似文献
132.
María Abreu-Sepúlveda Dominique E. Williams Ashfia Huq Chetan Dhital Yunchao Li M. Parans Paranthaman Karim Zaghib A. Manivannan 《Ionics》2016,22(3):317-325
Titanium, tantalum-substituted Li7La3Zr2-xAxO12 (LLZO, A?=?Ta, Ti) garnets, and chromium-substituted La(2/3)-xLi3xTi1-yCryO3 (LLTO) perovskites were prepared by a conventional solid-state reaction and the Pechini processes. The desired crystal phases were obtained by varying the calcination temperature and time, as well as the substitution concentration. All samples indicated decomposition of the precursors when heated above 750 °C and formation of the desired phase after heat treatment at higher temperatures. Neutron diffraction data shows the formation of a predominant cubic phase in the case of Ta-LLZO, and monoclinic phase with minor impurity phases for Cr-LLTO. Ionic conductivity for Ti-LLZO (Li7La3Zr1.4Ti0.6O12), Ta-LLZO (Li6.03La3Zr1.533Ta0.46O12), and Cr-LLTO (La(2/3)-xLi3xTi0.9Cr0.1O3) at room temperature were found to be 5.21?×?10?6, 1.01?×?10?6, and 1.2?×?10?4 S cm?1, respectively. The activation energies of the compounds were determined from the Arrhenius plot and were 0.44 eV (Ti0.6-LLZO), 0.54 eV (Ta0.5-LLZO), and 0.20 eV (Cr0.1-LLTO). 相似文献
133.
Omar El-Fallah Emmanuel Fricain Karim Kellay Javad Mashreghi Thomas Ransford 《Constructive Approximation》2016,44(2):269-281
In most classical holomorphic function spaces on the unit disk in which the polynomials are dense, a function f can be approximated in norm by its dilates \(f_r(z):=f(rz)~(r<1)\). We show that this is not the case for the de Branges–Rovnyak spaces \(\mathcal{H}(b)\). More precisely, we exhibit a space \(\mathcal{H}(b)\) in which the polynomials are dense and a function \(f\in \mathcal{H}(b)\) such that \(\lim _{r\rightarrow 1^-}\Vert f_r\Vert _{\mathcal{H}(b)}=\infty \). On the positive side, we prove the following approximation theorem for Toeplitz operators on general de Branges–Rovnyak spaces \(\mathcal{H}(b)\). If \((h_n)\) is a sequence in \(H^\infty \) such that \(\Vert h_n\Vert _{H^\infty }\le 1\) and \(h_n(0)\rightarrow 1\), then \(\Vert T_{\overline{h}_n}f-f\Vert _{\mathcal{H}(b)}\rightarrow 0\) for all \(f\in \mathcal{H}(b)\). Using this result, we give the first constructive proof that, if b is a nonextreme point of the unit ball of \(H^\infty \), then the polynomials are dense in \(\mathcal{H}(b)\). 相似文献
134.
In this paper we settle two long-standing questions regarding the combinatorial complexity of Minkowski sums of polytopes: We give a tight upper bound for the number of faces of a Minkowski sum, including a characterization of the case of equality. We similarly give a (tight) upper bound theorem for mixed facets of Minkowski sums. This has a wide range of applications and generalizes the classical Upper Bound Theorems of McMullen and Stanley.Our main observation is that within (relative) Stanley–Reisner theory, it is possible to encode topological as well as combinatorial/geometric restrictions in an algebraic setup. We illustrate the technology by providing several simplicial isoperimetric and reverse isoperimetric inequalities in addition to our treatment of Minkowski sums. 相似文献
135.
Lee CJ Lee SY Karim MR Lee MS 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,68(5):1313-1319
In this study, the adsorption orientation for 2-mercaptobenzothiazole (MBT) and 2-mercaptobenzoxazole (MBO) on to silver mirror and silver sol substrates have been studied by surface enhanced Raman scattering (SERS). The MBT and MBO were chemisorbed on both silver mirror and silver sol after deprotonation with a tilted orientation to the silver surfaces. The surface enhanced properties of MBT and MBO showed that the substrate of silver mirror was superior to the sliver sol. The SERS spectra of MBT and MBO revealed that both of the MBT and MBO were adsorbed on silver surfaces strongly by a common sulfur molecule and a sulfur atom from MBT and an oxygen atom from MBO. Therefore, the adsorption orientation of MBT and MBO was little tilted perpendicularly to the silver surfaces. The adsorption geometry did not undergo any significant changes in acidic and basic solutions. It showed that the adsorption orientation for MBT and MBO were stable in the both solutions. 相似文献
136.
Chen W McCormack PJ Mohammed K Mbafor W Roberts SM Whittall J 《Angewandte Chemie (International ed. in English)》2007,46(22):4141-4144
137.
Karim K Klasson KT Drescher SR Ridenour W Borole AP Al-Dahhan MH 《Applied biochemistry and biotechnology》2007,142(3):231-242
Anaerobic digestion kinetics study of cow manure was performed at 35°C in bench-scale gas-lift digesters (3.78 l working volume)
at eight different volatile solids (VS) loading rates in the range of 1.11–5.87 g l−1 day−1. The digesters produced methane at the rates of 0.44–1.18 l l−1 day−1, and the methane content of the biogas was found to increase with longer hydraulic retention time (HRT). Based on the experimental
observations, the ultimate methane yield and the specific methane productivity were estimated to be 0.42 l CH4 (g VS loaded)–1 and 0.45 l CH4 (g VS consumed)–1, respectively. Total and dissolved chemical oxygen demand (COD) consumptions were calculated to be 59–17% and 78–43% at 24.4–4.6 days
HRTs, respectively. Maximum concentration of volatile fatty acids in the effluent was observed as 0.7 g l–1 at 4.6 days HRT, while it was below detection limit at HRTs longer than 11 days. The observed methane production rate did
not compare well with the predictions of Chen and Hashimoto’s [1] and Hill’s [2] models using their recommended kinetic parameters. However, under the studied experimental conditions, the predictions of
Chen and Hashimoto’s [1] model compared better to the observed data than that of Hill’s [2] model. The nonlinear regression analysis of the experimental data was performed using a derived methane production rate
model, for a completely mixed anaerobic digester, involving Contois kinetics [3] with endogenous decay. The best fit values for the maximum specific growth rate (μ
m) and dimensionless kinetic parameter (K) were estimated as 0.43 day–1 and 0.89, respectively. The experimental data were found to be within 95% confidence interval of the prediction of the derived
methane production rate model with the sum of residual squared error as 0.02. 相似文献
138.
Benkoski JJ Bowles SE Korth BD Jones RL Douglas JF Karim A Pyun J 《Journal of the American Chemical Society》2007,129(19):6291-6297
The assembly and direct imaging of ferromagnetic nanoparticles into one-dimensional mesostructures (1-D) are reported. Polymer-coated ferromagnetic colloids (19 nm, 24 nm) were assembled at a crosslinkable oil-water interface under both magnetic field induced and zero-field conditions and permanently fixed into 1-D mesoscopic polymer chains (1-9 mum) in a process referred to as Fossilized Liquid Assembly (FLA). In the FLA process, nanoparticle chains were fixed at the oil interface through photopolymerization, enabling direct visualization of organized mesostructures using atomic force microscopy. Using the FLA methodology, we systematically investigated different conditions and demonstrated that dispersed ferromagnetic colloids possess sufficient dipolar interactions to organize into mesoscopic assemblies. Application of an external magnetic field during assembly enabled the formation of micron-sized chains which were aligned in the direction of the applied field. This universal methodology is an attractive alternative technique to cryogenic transmission electron microscopy (cryo-TEM) for the visualization of nanoparticle assembly in dispersed organic media. 相似文献
139.
Bistri O Mazeau K Auzély-Velty R Sollogoub M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(31):8847-8857
New beta-cyclodextrin (beta-CD) dimeric species have been synthesised in which the two CD moieties are connected by one or two hydrophilic oligo(ethylene oxide) spacers. Their complexation with sodium adamantylacetate (free adamantane) and adamantane-grafted chitosan (AD-chitosan) was then studied by different complementary techniques and compared with their hydrophobic counterparts that contain an octamethylene spacer. Isothermal titration calorimetry experiments have demonstrated that the use of hydrophilic spacers between the two CDs instead of aliphatic chains makes almost all of the CD cavities available for the inclusion of free adamantane. Investigation of the interaction of the CDs with AD-chitosan by viscosity measurements strongly suggests that the molecular conformation of the CD dimeric species plays a crucial role in their cross-linking with the biopolymer. The derivative doubly linked with hydrophilic arms, also called a duplex, has been shown to be a more efficient cross-linking agent than its singly bridged counterpart, referred to as a dimer. Hence, only 0.5 molar equivalents of the hydrophilic duplex with respect to adamantane was required to obtain the maximum viscosity, whereas in the case of the duplex with aliphatic spacers, the maximum viscosity was achieved with a [duplex]/[AD] ratio of about 1.7 (corresponding to a [CD]/[AD] ratio of 2.5), but with a higher value. To clarify the relationships between the molecular architecture and complexation properties, computational studies were also performed that clearly confirmed the importance of double bridging. 相似文献
140.
Bouchmella K Boury B Dutremez SG van der Lee A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(21):6130-6138
The structural characterization of molecular assemblies constructed from imidazolyl-containing haloalkenes and haloalkynes is reported. 1-(3-Iodopropargyl)imidazole (2) and 1-(2,3,3-triiodoallyl)imidazole (5) were synthesized from 1-propargylimidazole (1). In the solid state, these wholly organic modules self-assemble through N...I halogen-bonding interactions, thus giving rise to polymeric chains. The N...I interaction observed in 2 (d(N...I)=2.717 A, angle-spherical C(sp)-I...N=175.8 degrees) is quite strong relative to previously reported data. The N...I interaction in 5 (d(N...I)=2.901 A, angle-spherical C(sp2)-I...N=173.6 degrees) is weaker, in accordance with the order C(sp)-X<--base>C(sp2)-X<--base. Compound 5 was found to give a 1:1 cocrystal 4 with morpholinium iodide (6). In the X-ray crystal studies of 4, N...I halogen-bonding interactions similar to those observed in 5 were shown not to be present, as the arrangement of the molecules is governed by two interwoven hydrogen-bonding networks. The first network involves N-H...O interactions between nearby morpholinium cations, and the second network is based on N-H...N hydrogen bonding between morpholinium cations and imidazolyl groups. Both hydrogen-bonding schemes are charge-assisted. Halogen bonding is not completely wiped out, however, as the triiodoalkene fragment forms a halogen bond with an iodide anion in its vicinity (d(I...I)=3.470 A, angle-spherical C(sp2)-I...I=170.7 degrees). X-ray crystal studies of 6 show a completely different arrangement from that observed in 4, namely, N-H...O interactions are not present. In crystalline 6, morpholinium cations are interconnected through C-H...O bridges (d(H...O)=2.521 and 2.676 A), and the NH2+ groups interact with nearby iodide anions (d(H...I)=2.633 and 2.698 A). 相似文献