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991.
用紧束缚EHT晶体轨道方法对一维〔M(tmp)〕_2ReO_4(M=Ni、Cu、Pd)聚合物进行了能带计算,利用键向量近似方法对能带的结构及组成进行了讨论。结果表明,该类型聚合物具有不同的导电机理,并进一步研究了环平面间的成键性质及转角改变对聚合物导电性能的影响。  相似文献   
992.
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   
993.
A star network polymer with a pentaerythritol core linking four PEG-block polymeric arms was synthesized, and its corresponding gel polymer electrolyte based on lithium perchlorate and plasticizers EC/PC with the character being colorless and highly transparent has been also prepared. The polymer host was characterized and confirmed to be of a star network and an amorphous structure by FTIR, ^1H NMR and XRD studies. The polymer host hold good mechanical properties for pentaerythritol cross-linking. Maximum ionic conductivity of the prepared polymer electrolyte has reached 8.83 × 10 ^-4 S·cm^-1 at room temperature. Thermogravimetry (TG) of the polymer electrolyte showed that the thermal stability was up to at least 150 ℃. The gel polymer electrolyte was further evaluated in electrochromic devices fabricated by transparent PET-ITO and electrochromically active viologen derivative films, and its excellent performance promised the usage of the gel polymer electrolyte as ionic conductor material in electrochrornic devices.  相似文献   
994.
(R)-2-羟基-4-苯基丁酸乙酯的合成   总被引:4,自引:0,他引:4  
林文清  张晓梅  宓爱巧 《合成化学》2002,10(5):385-390,456
综述了血管紧张素转化酶抑制剂类治疗高血压和充血性心力衰竭药物的关键中间体(R)-2-羟基-4-苯基丁酸乙酯的合成方法。参考文献25篇。  相似文献   
995.
为研究老年人彩色视觉频率响应特性,获取彩度对比敏感度与空间频率之间的函数关系,本文在LCH均匀颜色空间基础上,固定明度和色调角值,以彩度作为变量,设计人眼彩度对比敏感度实验,进行人眼视觉观察实验。获得彩度对比敏感度与空间频率的关系,并构建指数型对比敏感度函数模型。经分析表明老年人眼彩度对比敏感度随着空间频率的增加,产生先升高再缓慢降低的变化,各色调角下彩度对比度存在差异。经分析人眼对比敏感度差异与人眼视觉辨色特性有很大的相关性。并且,将构建的对比敏感度函数模型用于实现基于人眼视觉系统的滤波处理。  相似文献   
996.
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   
997.
镧系与二甘醇-二-(邻羟基苯基)醚配合物的合成与表征   总被引:4,自引:0,他引:4  
本文合成14种镧系高氯酸盐及硝酸盐分别与二甘醇-二-(邻羟基苯基)醚(记为EO_2(HOP)_2,EO=ethylene oxide,HOP为邻羟基苯基)形成的新配合物,确证组成为Ln(ClO_4)_3·EO_2(HOP)_2·nH_2O(Ln:La-Eu,n=10,Ln:Gd,Dy-Tm,Y,n=7),La_3(NO_3)_9·(EO_2(HOP)_2)_2·3H_2O及La(ClO_4)_2·EO_2H(OP)_25H_2O。文中研究了配合物红外,紫外、~1HNMR谱及~(13)C纵向弛豫时间T_1等,并讨论了共存阴离子、溶剂及配体不同端基对成配的影响。  相似文献   
998.
In this paper, the nanosecond transient absorption spectra and the fluorescence spectraof Hypocrellin A(HA) are examined in solvents of varying polarity. There are three absorp-tion bands in dilute HA solutions: Ⅰa, Ⅱa are defined as the triplet-triplet absorption ofHA, the band Ⅲa is supposed to be the absorption of the solvent--sepatated ion pair (SSIP).In more concentrated solutions, only the absorption of SSIP was observed. The effects ofsolvent polarity on transient absorption spectra and fluorescence spectra of HA and the effectof oxygen on the intensities of the fluorescence of HA are discussed. Then a reasonablemechanism for the photolysis of HA is proposed.  相似文献   
999.
前报中已证明用三氟化硼-环氧氯丙烷(ECH)引发四氢呋喃(THF)聚合具有较高的引发效率,并对在Ac_2O、水和无水存在下的聚合反应进行了研究。本文报道1,4-丁二醇(BG)对BF_3引发THF聚合反应的影响。通常认为在BG存在下,BF_3是不能引发THF聚合的,但本工作证明BG是有效的分子量调节剂,制备分子量在  相似文献   
1000.
本文讨论了甲基丙烯酸羟乙酯和甲基丙烯酸在乙醇中进行溶液聚合时,借助酯交换反应,在该亲水体系中引入第三疏水组分,从而制备三元共聚物的可行性.  相似文献   
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