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排序方式: 共有8188条查询结果,搜索用时 15 毫秒
91.
92.
Abstract With comparable molar quantities, chromotropic acid reacts with compounds containing aldehyde groups -CHO e.g. with formadehyde or glyoxylic acid to form cyclic compounds with rings containing four chromotropic acid fragments — cyclotetrachromotropylene derivatives. The cyclic compounds, due to the presence of a cavity in the molecule, can play the part of host and complex smaller molecules, which has been confirmed on the basis of triethylamine by the 1H-NMR measurements. Using spectrophotometric method the stability constant of 1:1 complex formed between Ti(IV) and cyclic compound chromotropic acid with formaldehyde has been determined - K = (9,0 ± 0,1) 104. 相似文献
93.
94.
Maria Gil Elena Bermejo Alfonso Castieiras Heloisa Beraldo Douglas X. West 《无机化学与普通化学杂志》2000,626(11):2353-2360
Pyridyl bis(N(4)‐substituted thiosemicarbazones), in which the substituents replacing the NH2 group on the thiosemicarbazone moieties are piperidyl, H2Plpip; hexamethyleneiminyl, H2Plhexim; diethylamino, H2Pl4DE; and dipropylamino, H2Pl4DP, have been synthesized. These bis(thiosemicarbazones) and their nickel(II) complexes have been characterized with IR, electronic, mass, and 1H and 13C NMR spectra. Crystal structures have been solved for H2Plpip and all four nickel(II) complexes. H2Plpip does not possess hydrogen bonding between the thiosemicarbazone moieties, but is in the Z isomeric form with intramolecular hydrogen bonding from both thiosemicarbazone moieties to pyridine nitrogen atoms. The nickel(II) complexes possess square‐planar N2S2 (i. e., imine nitrogen and thiolato sulfur atoms) centers and the two pyridine ring nitrogen atoms are not coordinated. 相似文献
95.
Effects of substituent and solvent on the structure and spectral properties of maleimide derivatives
Chin-Kuen Tai Yih-Jiun Lin Pao-Ling Yeh Yi-Ren Tzeng Yu-Ma Chou Bo-Cheng Wang 《Journal of Molecular Structure》2008,860(1-3):58-63
The maximum absorption wavelength , emission wavelength (λem) and the related oscillator strength (f) of the maleimides in the ground and first excited states were calculated by using the DFT, CIS and the time-dependent density functional theory (TD-DFT) methods, where the molecular structures were optimized by DFT/B3LYP/6-31G* calculation. Solvent effects on the maleimides were examined using the PCM simulation at DFT/B3LYP level with the 6-31G* basis set. For N-substituted maleimide, the substituent gives only a slight influence on the maleimide chromophore, while planar conformation of PhMLH leads to the improvement in π-delocalization from substituent to maleimide unit. For 3,4-substituted maleimide, the steric repulsion between substituent and maleimide chromophore influences the extent of π-delocalization and the molecular conformation. The calculated and λem of maleimides are in good agreement with the experimental data. In the gas phase, both absorption and emission peaks are red-shift as compared to the non-substituted maleimide. Under solvent environment, the more planar conformation of PhMLH shows a blue-shift in the calculated and λem as compared with other N-substituted maleimides. For 3,4-substituted maleimides, the effect of substitution produces the most significant spectral red-shift as compared to other maleimides. 相似文献
96.
Asensio González Xavier Solans Elies Molins 《Journal of organometallic chemistry》2008,693(12):2119-2131
The synthesis and characterization of pyrazole derivatives of general formula [C6H4-4-R-1-{(3,5-Me2-C3N2)-CH2-(η5-C5H4)Fe(η5-C5H5)}] [R = OMe (1a) or H (1b)] with a ferrocenylmethyl substituent are described.The study of the reactivity of compounds 1 with palladium(II) acetate has allowed the isolation of complexes (μ-AcO)2[Pd{κ2-C,N-C6H3-4-R-1-[(3,5-Me2-C3N2)-CH2-(η5-C5H4)Fe(η5-C5H5)]}]2 (2) [R = OMe (2a) or H (2b)] that contain a bidentate [C(sp2, phenyl), N]− ligand and a central “Pd(μ-AcO)2Pd” unit.Furthermore, treatment of 2 with LiCl produced complexes (μ-Cl)2[Pd{κ2-C,N-C6H3-4-R-1-[(3,5-Me2-C3N2)-CH2-(η5-C5H4)Fe(η5-C5H5)]}]2 (3) [R = OMe (3a) or H (3b)] that arise from the replacement of the acetato ligands by the Cl−.Compounds 2 and 3 also react with PPh3 giving the monomeric complexes [Pd{κ2-C,N-C6H3-4-R-1-[(3,5-Me2-C3N2)-CH2-(η5-C5H4)Fe(η5-C5H5)]}X(PPh3)] {X− = AcO− and R = OMe (5a) or H (5b) or X− = Cl− and R = OMe (6a) or H (6b)}, where the phosphine is in a cis-arrangement to the metallated carbon atom. Treatment of 3 with thallium(I) acetylacetonate produced [Pd{κ2-C,N-C6H3-4-R-1-[(3,5-Me2-C3N2)-CH2-(η5-C5H4)Fe(η5-C5H5)]}(acac)] (7) [R = OMe (7a) or H (7b)]. Electrochemical studies of the free ligands and the cyclopalladated complexes are also reported. The dimeric complexes 3 also react with MeO2C-CC-CO2Me (in a 1:4 molar ratio) giving [Pd{(MeO2C-CC-CO2Me)2C6H3-4-R-1-[(3,5-Me2-C3N2)-CH2-(η5-C5H4)Fe(η5-C5H5)]}Cl] (8) [R = OMe (8a) or H (8b)], which arise from the bis(insertion) of the alkyne into the σ{Pd-C(sp2, phenyl)} bond of 3. 相似文献
97.
Erich Kleinpeter Andreas Koch Bagrat A. Shainyan 《Journal of Molecular Structure》2008,863(1-3):117-122
The spatial magnetic properties (Through Space NMR Shieldings – TSNMRS) of two cyclobutadiene derivatives (2 and 5) and of a number of cyclobutadiene dianion derivatives (3, 4 and 6–8) have been calculated by the GIAO perturbation method employing the Nucleus-Independent Chemical Shift (NICS) concept of P. v. Ragué Schleyer, and visualized as Iso-Chemical-Shielding Surfaces (ICSS) of various size and direction. TSNMRS values can be successfully employed to quantify and visualize the (anti)aromaticity of the compounds studied and to discuss the influence of Li+ complexation to cyclobutadiene dianion (4a, 7 and 8) on planar 4c,6e or three-dimensional 6c,6e aromaticity. 相似文献
98.
A synthesis of chiral optically active 3-hydroxyoxindoles with 1,3-disubstituted 2,2-dimethyl-cyclobutane structural fragment
by the Et2NH-catalyzed aldol reaction of indoline-2,3-diones with (−)-(1S,3S)-pinonic acid derivatives is described.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1540–1543, July, 2008. 相似文献
99.
Weiyu Li Sen Li Dr. Claire Empel Prof. Dr. Rene M. Koenigs Prof. Dr. Lei Zhou 《Angewandte Chemie (International ed. in English)》2023,62(42):e202309947
A photocatalytic self-(3+2) cycloaddition of vinyldiazo compounds is described, which provides cyclopentene derivatives with conservation of one diazo functional group. Experimental insights and density functional theory indicate that the reaction is triggered by an unusual single electron oxidation of vinyldiazo compounds, while the photolysis for the generation of free carbene species is not involved. The synthetic applications of the resulting cyclopentenyl α-diazo compounds were demonstrated based on the rich chemistry of the diazo functional group. 相似文献
100.
Wenbo Huang Liqiao Shi Manli Liu Zhigang Zhang Fang Liu Tong Long Shaohua Wen Daye Huang Kaimei Wang Ronghua Zhou Wei Fang Hongtao Hu Shaoyong Ke 《Molecules (Basel, Switzerland)》2022,27(5)
Primary arylsulfonamide functional groups feature prominently in diverse pharmaceuticals. However, natural arylsulfonamides are relatively infrequent. In this work, two novel arylsulfonamide natural products were first synthesized, and then a series of novel molecules derived from natural arylsulfonamides were designed and synthesized, and their in vitro cytotoxic activities against A875, HepG2, and MARC145 cell lines were systematically evaluated. The results indicate that some of these arylsulfonamide derivatives exhibit significantly good cytotoxic activity against the tested cell lines compared with the control 5-fluorouracil (5-FU), such as compounds 10l, 10p, 10q, and 10r. In particular, the potential molecule 10q, containing a carbazole moiety, exhibited the highest inhibitory activity against all tested cell lines, with IC50 values of 4.19 ± 0.78, 3.55 ± 0.63, and 2.95 ± 0.78 μg/mL, respectively. This will offer the potential to discover novel drug-like compounds from the sparsely populated area of natural products that can lead to effective anticancer agents. 相似文献