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131.
The Transition‐Metal‐Like Behavior of B2(NHC)2 in the Activation of CO: HOMO–LUMO Swap Without Photoinduction 下载免费PDF全文
Dr. Huaiyu Zhang Prof. Zexing Cao Prof. Wei Wu Prof. Yirong Mo 《Angewandte Chemie (International ed. in English)》2018,57(40):13076-13081
It is a current trend to explore multi‐bonded and unsaturated main group compounds that can interact with small molecules, in order to find non‐metal catalysts. Notably, Braunschweig et al. found that diboryne stabilized by N‐heterocyclic carbenes (NHCs) can bind and activate CO. Here we explore the bonding nature of B2(NHC)2 and its activation mechanism for CO from a novel theoretical perspective. While the ground state of B2 is of a single bond, the approach of NHCs excites B2 to its third excited state of a triple bond with two significant σ‐holes at the two ends. The subsequent electrostatic attraction drives the formation of B2(NHC)2. However, only one of the two π bonds (HOMOs) of B2(NHC)2 fits to one of the degenerate LUMOs of CO. Interestingly, the strong steric repulsion between CO and B2(NHC)2 leads to the HOMO–LUMO swap in the latter. Subsequently, both HOMO and HOMO?1 of B2(NHC)2 can effectively interact with the two π* anti‐bonding orbitals (LUMO and LUMO+1) of CO, resulting in substantial electron back‐donation and the ultimate activation of CO. 相似文献
132.
近年来亚硝酸甲酯分子(CHa0NO)的光解动力学研究十分活跃{‘5],主要集中在紫外激光的单光子解离的机理,光解过程的矢量相关性质和光解产物的态分布.CH30NO分子的解离能D。(CH30-NO)=174kJ·mol‘,若单从能量上看,人<689。的光就能使其解离,但人>400urn的光解离研究还未见报导.*H30*0分子在人>40onm的强激光场下是充电离还是先解离,是单光子解离还是多光子解离,以及通过哪个电子态解离都不清楚.时间飞行质谱不仅具有质量分辨率高、范围宽,而且响应快,因此适合做光解光电离过程初生态产物的探测.特别是时间飞… 相似文献
133.
本文提出平行催化体系的对位叠式循环方波伏安法,并对共作了系统的研究,推导了这一方法的催化电流理论方程,并用验验证这理论的正确性,得到其各脉冲电流皆为同方向,对位叠式循环催化电流相当于将电流叠加4次,而波形不受方波幅度大小的影响,因而灵敏度和分辨率有较大提高,优于其它方波伏安法。 相似文献
134.
Mo C Zhang W Liu L Wang L Xiao H 《Combinatorial chemistry & high throughput screening》2012,15(3):242-252
Aging and its related diseases are severe issues in modern society. Many efforts have been made to understand the mechanisms of aging and to find the ways to prevent age-related diseases. Identifying the compounds targeting aging-related signals is a challenging work because there are so many proteins and signals involved. Recently, alone with the progresses in high throughput screening (HTS) technology, increasing numbers of small molecules targeting aging-related pathologic processes have been identified. In this review, we introduce the basic workflow, classification and assay strategies of HTS technology, and sort out known small molecules identified via HTS technology by their roles in aging related diseases, such as neural degenerative diseases, diabetes and tumors. Given the fact that application of HTS on aging research is still at an early stage, we also summarize the cellular mechanisms about aging process, paralleled with the compounds which can modulate the functions of proteins important for aging signals. Finally, we briefly discuss some advanced HTS technologies for their potent applications on the discovery of anti-aging compounds. The main purpose of this review is to provide updated and useful information to those who are interested in pharmacology and HTS technology, but not familiar with aging biology, or vice versa. 相似文献
135.
Lanthanide doping not only works as sensitizer and activator, but also plays an important role to facilitate the growth of nanocrystal and to control the size, shape, and property of nanocrystals. Here, reported was the synthesis of monodisperse Ba(2)LaF(7) nanocrystals with the size of sub-10nm through a solvothermal method. We found the dopants of Ho(3+), Er(3+), or Yb(3+) facilitated the growth of Ba(2)LaF(7) nanocrystals obviously to a certain size within a shorter reaction time. Similar phenomenon can also be observed in the synthesis of LaF(3) nanocrystals. We find that Ln(3+) (e.g., Ho(3+), Er(3+), or Yb(3+)) with smaller radius can reduce the nucleation energy and lead to heterogeneous nucleation, which favors the growth of Ba(2)LaF(7) nanocrystals obviously. In addition, intense upconversion emission can be observed from Ln(3+)-doped Ba(2)LaF(7) nanocrystals under the 980 nm laser excitation, providing great potential application in biological imaging. Especially, Ba(2)LaF(7):Yb/Er (20/1 mol%) nanocrystals present more intense upconversion emission than α-NaYF(4):Yb/Er (20/1 mol%) nanocrystals under the same conditions. 相似文献
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138.
螯合型二甘醇钛酸酯的合成及其催化性能研究 总被引:3,自引:0,他引:3
报导了两种新的螯合型二甘醇钛酸酯的合成方法,进行了IR和UV鉴定,并作为酯化反应催化剂催化合成了邻苯二甲酸二辛酯。研究了酯化反应转化率与反应时间、反应温度及催化剂用量的关系,探讨了催化剂结构与催化性能的关系。 相似文献
139.
人工神经网络及其在分析化学中的应用 总被引:31,自引:1,他引:31
人工神经网络是一种新兴的计算方法,有着广阔的发展前途,目前在分析化学领域已经有了多方面的应用。本文简要介绍了人工神经网络的原理及其在分析化学中的应用。 相似文献
140.