排序方式: 共有77条查询结果,搜索用时 31 毫秒
71.
Prof. Dr. Andreas Gansäuer Karsten Knebel Christian Kube Dr. Maurice van Gastel Asli Cangönül Prof. Dr. Kim Daasbjerg Tim Hangele Michael Hülsen Prof. Dr. Michael Dolg Dr. Joachim Friedrich 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(9):2591-2599
The mechanism of catalytic 4‐exo cyclizations without gem‐dialkyl substitution was investigated by a comparison of cyclic voltammetry, EPR, and computational studies with previously published synthetic results. The most active catalyst is a super‐unsaturated 13‐electron titanocene(III) complex that is formed by supramolecular activation through hydrogen bonding. The template catalyst binds radicals via a two‐point binding that is mandatory for the success of the 4‐exo cyclization. The computational investigations revealed that formation of the observed trans‐cyclobutane product is not possible from the most stable substrate radical. Instead, the most stable product is formed with the lowest energy of activation from a disfavored substrate in a Curtin–Hammett related scenario. 相似文献
72.
Asli Karakas Hüseyin Ünver 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2010,75(5):1492-1496
(E)-N-(4-Nitrobenzylidene)-2,6-dimethylaniline (1) and (E)-N-(4-nitrobenzylidene)-2,3-dimethylaniline (2) have been synthesized. The crystal structures of both compounds have been defined by X-ray diffraction analysis. The maximum one-photon absorption (OPA) wavelengths recorded by quantum mechanical computations using a configuration interaction (CI) method are estimated in the UV region to be shorter than 450 nm, showing good optical transparency to the visible light. To provide an insight into the microscopic third-order nonlinear optical (NLO) properties of the investigated molecules, both dispersion-free (static) and also frequency-dependent (dynamic) linear polarizabilities (α) and second hyperpolarizabilities (γ) at λ = 825–1125 nm and 1050–1600 nm wavelength areas have been computed using time-dependent Hartree–Fock (TDHF) method. According to the ab initio calculation results, the title molecules exhibit second hyperpolarizabilities with non-zero values, implying microscopic third-order NLO behavior. 相似文献
73.
A series of novel calix[4]arene-based Mannich (5 and 6) and Schiff base (9–11) receptors have been synthesized and characterized by various analytical techniques. Competitive two-phase extraction experiments of these novel calix[4]arene amine- and imine-containing derivatives revealed a strong affinity for dichromate anions . The protonated alkylinium form of 5, 6 and 9–11 proved to be effective extractants for transferring the dichromate anions from an aqueous into an organic phase. Moreover, the extraction of dichromate anions by 5 and 9 in the presence of competitive anions such as F?, Cl?, Br?, , , and showed that 5 and 9 could be selective anion receptors for dichromate anions in the presence of those anions. 相似文献
74.
Asli Celikyilmaz I. Burhan Turksen 《International Journal of Approximate Reasoning》2010,51(8):869-882
We analyze the impact of imprecise parameters on performance of an uncertainty-modeling tool presented in this paper. In particular, we present a reliable and efficient uncertainty-modeling tool, which enables dynamic capturing of interval-valued clusters representations sets and functions using well-known pattern recognition and machine learning algorithms. We mainly deal with imprecise learning parameters in identifying uncertainty intervals of membership value distributions and imprecise functions. In the experiments, we use the proposed system as a decision support tool for a production line process. Simulation results indicate that in comparison to benchmark methods such as well-known type-1 and type-2 system modeling tools, and statistical machine-learning algorithms, proposed interval-valued imprecise system modeling tool is more robust with less error. 相似文献
75.
Karakaş A Elmali A Unver H Svoboda I 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(13-14):2979-2987
N-(4-nitrobenzylidene)-o-fluoroamine (1) and N-(3-nitrobenzylidene)-p-fluoroamine (2) have been synthesized. The crystal structures of both compounds have been defined by X-ray diffraction analysis, and characterized by FT-IR and UV-visible instrumental methods. The recorded spectrum by UV-visible spectroscopy for the investigated compounds show good transparency in the visible region, and have solvatochromic behavior in the UV region, implying nonzero microscopic first hyperpolarizability. We also report ab initio quantum chemical calculations of the electric dipole moments (mu) and the first hyperpolarizabilities (beta) of the studied compounds. Our results suggest that the investigated ligands might have microscopic nonlinear optical (NLO) behavior with nonzero values. 相似文献
76.
Mehmet Hakan Morcali Asli Baysal 《International journal of environmental analytical chemistry》2013,93(14):1397-1414
ABSTRACTIn the present study, novel bioconjugated sorbents (peptide and oligo-nucleotide on the cobalt aluminate nanomaterials) were used to remove lead through miniaturised process and the concentration of lead was measured by inductively coupled plasma mass spectrometry. For this aim, lead was collected on sorbent in mini tube, and the influences of experimental conditions (e.g. pH of sample, amount of sorbent, concentration of eluent, foreign ions) and retention parameters on the recovery of the lead element were examined. After the optimisation of experimental parameters, a successful separation was obtained at pH 7.5 with high (>95%) quantitative recovery and high precision (<10% relative standard deviation). Using the proposed bioconjugated sorbents, the lead in sea water and tap water samples could be practically and easily removed with 95% confidence level. The detection limits of this method for lead using oligonucleotide and peptide on the cobalt aluminate nanomaterials were 0.14 and 0.12 µg/L (3σ, N = 10) with sample-matched blanks. This method can be widely used as promising and cost-effective nanomaterials to remove lead from water systems. 相似文献
77.
Ahsen Sare Yalın Buse Sündü Melek Sermin Özer Ayoub Abdelkader Mekkaoui Soufiane El Houssame Önder Metin 《应用有机金属化学》2023,37(1):e6943
A facile wet-chemical protocol for the synthesis of bimetallic CuPd alloy nanoparticles (NPs) anchored on mesoporous graphitic carbon nitride (m-gCN), serving as both stabilizer and support material, was presented herein. The presented protocol allowed to synthesize nearly monodisperse CuPd alloy NPs with an average particle size of 3.9 ± 0.9 nm without use of any additional surfactants and to prepare CuPd/m-gCN nanocatalysts with different Cu/Pd compositions (Cu25Pd75/m-gCN, Cu35Pd65/m-gCN, Cu16Pd74/m-gCN, Cu32Pd68/m-gCN, Cu10Pd90/m-gCN, and Cu50Pd50/m-gCN). After the detailed characterization of CuPd/m-gCN nanocatalysts, they were utilized as catalysts in the dehydrogenation of terpenes. Among all tested nanocatalysts, Cu50Pd50/m-gCN showed the highest activity in terms of the product yields within the same reaction time. Various parameters influencing the catalytic activity of Cu50Pd50/m-gCN were studied using himachalene as a model substrate and the optimum conditions were determined. Under the optimized reaction conditions, the catalytic application of Cu50Pd50/m-gCN nanocatalysts was extended to nine different terpenes and the corresponding products were obtained in high conversion yields (>90%) under mild conditions. A reusability test showed that Cu50Pd50/m-gCN nanocatalysts can be re-used up to four cycles without significant loss in their initial activity. 相似文献