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141.
Wen Ma Yu-Peng Tian Sheng-Yi Zhang Jie-Ying Wu Hoong-Kun Fun Suchada Chantrapromma 《Transition Metal Chemistry》2006,31(1):97-102
A new diferrocenyl-substituted macrocyclic ligand (H2L) and its complexes ML(M = CuII, NiII, ZnII, CdII) were prepared and characterized by IR, elemental analysis, absorption spectra and FAB mass spectra. The ferrocenyl-substituted
macrocyclic ligand was characterized by single crystal X-ray diffraction analysis. The superconjugative effect of the cyclopentadienyl
(CP) rings increase the activity of the hydrogen atoms in the tetra-azacyclotetradecane macrocyclic ligand. The imine nitrogen
atoms lose two protons and coordinate to the metal. The electrochemical properties of these compounds are discussed. 相似文献
142.
Mingjian Wen Samuel M. Blau Evan Walter Clark Spotte-Smith Shyam Dwaraknath Kristin A. Persson 《Chemical science》2021,12(5):1858
A broad collection of technologies, including e.g. drug metabolism, biofuel combustion, photochemical decontamination of water, and interfacial passivation in energy production/storage systems rely on chemical processes that involve bond-breaking molecular reactions. In this context, a fundamental thermodynamic property of interest is the bond dissociation energy (BDE) which measures the strength of a chemical bond. Fast and accurate prediction of BDEs for arbitrary molecules would lay the groundwork for data-driven projections of complex reaction cascades and hence a deeper understanding of these critical chemical processes and, ultimately, how to reverse design them. In this paper, we propose a chemically inspired graph neural network machine learning model, BonDNet, for the rapid and accurate prediction of BDEs. BonDNet maps the difference between the molecular representations of the reactants and products to the reaction BDE. Because of the use of this difference representation and the introduction of global features, including molecular charge, it is the first machine learning model capable of predicting both homolytic and heterolytic BDEs for molecules of any charge. To test the model, we have constructed a dataset of both homolytic and heterolytic BDEs for neutral and charged (−1 and +1) molecules. BonDNet achieves a mean absolute error (MAE) of 0.022 eV for unseen test data, significantly below chemical accuracy (0.043 eV). Besides the ability to handle complex bond dissociation reactions that no previous model could consider, BonDNet distinguishes itself even in only predicting homolytic BDEs for neutral molecules; it achieves an MAE of 0.020 eV on the PubChem BDE dataset, a 20% improvement over the previous best performing model. We gain additional insight into the model''s predictions by analyzing the patterns in the features representing the molecules and the bond dissociation reactions, which are qualitatively consistent with chemical rules and intuition. BonDNet is just one application of our general approach to representing and learning chemical reactivity, and it could be easily extended to the prediction of other reaction properties in the future.Prediction of bond dissociation energies for charged molecules with a graph neural network enabled by global molecular features and reaction difference features between products and reactants. 相似文献
143.
Shihui Si Fenglian Ren Wen Cheng Shouzhuo Yao 《Analytical and bioanalytical chemistry》1997,357(8):1101-1105
To obtain new coatings for the preparation of piezoelectric immunosensors, the anodic polymerization of o-aminophenol (oAP),
o-phenylenediamine (oPD) and m-phenylenediamine (mPD) onto a gold-plated crystal has been studied. The possibility of immobilizing
an antibody (anti-S. paratyphi A) onto the crystal via the electropolymerized films was investigated. The poly-mPD film gave
the best results for immobilizing the antibody. With antibodies crosslinked on the poly-mPD film, a piezoelectric immuno-assay
for the detection of S. paratyphi A was proposed. The shift (ΔF=F20s−F400s, Hz) between the frequency at 20 s after the addition of sample (F20s), and that of 400 s (F400s) was used to construct a calibration graph, and shortening of the assay time was achieved. The S. paratyphi A concentration
in the range of 105–109 cells/ml can be measured by this method.
Received: 9 May 1996/Revised: 6 September 1996/Accepted: 19 September 1996 相似文献
144.
利用火焰原子吸收法直接测定羊睾丸,梅花鹿胎盘提取液中铅的含量,实验结果表明,两种提以液中均含有铅,梅花鹿胎盘提取液铅含量低于羊睾丸,透析液组高于超滤液组,这一结果为合理开发利用羊睾丸,梅花鹿胎盘提取液提供一定的数据。 相似文献
145.
Chiral quaternary ammonium salts derived from cinchonidine have been applied to catalyze the stereoselective iodolactonizations of trans-5-aryl-4-pentenoic acids leading to a mixture of two regioselectively iodolactonized products with fair to excellent yield (37-98%) and moderate enantioselectivity (exo = 42.0% ee, endo = 31.0% ee) under mild conditions. This work is the first example of asymmetric iodolactonization reaction in the presence of less than a stoichiometric amount of chiral reagent. 相似文献
146.
Redox reactions of Co(edta)? with Ru(NH3)5L2+ (L = 3- and 4-aminopyridine (AmPy)) were found to follow an outer-sphere electron transfer mechanism. The specific rate constants are (3.26 ± 0.03) × 102 and (3.07 ± 0.04) × 103 M?1S?1, for L = 3- and 4-AmPy, respectively, at μ, = 0.10 M LiClO4, pH = 8.0 (tris) and T = 25 °C. The rate constants of oxidations for a series of Ru(NH3)5L2+ complexes are higher than those of the corresponding Fe(CN)5L3- complexes by factors of 4 to 15 even after corrections for differences in reduction potentials and in charges of the complexes. Nonadiabaticity in the reactions of Fe(CN)5L3 complexes may account for the difference in the relative reactivities. 相似文献
147.
Jo‐Nan Chen Fang‐Ming Hsu Hui‐Chun Wang Chung‐Wen Wu Pao‐Swu Cheng Wen‐Liang Tsai 《中国化学会会志》2006,53(4):931-938
Four series of compounds 11?50 containing terminal alicyclic rings such as cyclohexylmethyl, cyclopentylmethyl, cyclobutylmethyl, and cyclopropylmethyl rings were synthesized and their liquid crystal behavior studied. The ring size and the length of flexible alkoxy chain influence the phase formation in different ways. While the smaller ring and the shorter alkoxy chain tend to favor the formation of the N phase, the larger ring and the longer alkoxy chain tend to favor the formation of the SmC phase. All the compounds except 11 and 21 exhibit SmA phases. The widest temperature range of the N, SmA, and SmC phases are found in the compounds 41 , 46 , and 20 , respectively, which are 75 °C for 41 , 115 °C for 46 , and 100 °C for 20 . 相似文献
148.
Y. H. Wen S. Lahiri Z. Qin X. L. Wu W. S. Liu 《Journal of Radioanalytical and Nuclear Chemistry》2002,253(2):263-265
An attempt has been made to develop a radiochemical methodology for the decontamination of a trace amount of radioactive cesium from a bulk amount of natural NaCl by liquid-liquid extraction (LLX). Open chain crown ethers, of amide type, namely, N,N,N",N"-tetraphenyl-3,6-dioxaoctanediamide (TDD), N,N,N",N"-tetraphenyl-3,6,9-trioxaundecanediamide and N,N"-dinaphthyl-N,N"-diphenyl-3,6-dioxaoctanediamide (DDD) have been chosen for this purpose. The separation factor between Cs and Na is the highest when 10-4M TDD dissolved in nitrobenzene is used as extractant and 0.4M picric acid at pH 5.0 is used as aqueous phase. About 60% Cs is extracted in this condition in a single run. 相似文献
149.
150.
A Novel Dihydroflavone from the Roots of Uvaria Macrophylla 总被引:1,自引:0,他引:1
A new dihydroflavone (1), named macrophyllol A, was isolated from the roots of Uvaria macrophylla. Its structure was elucidated on the basis of spectroscopic evidence. 相似文献