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相关概念视频

Stereoisomerism02:52

Stereoisomerism

11.7K
Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
11.7K
meta-Directing Deactivators: –NO2, –CN, –CHO, –⁠CO2R, –COR, –CO2H01:13

meta-Directing Deactivators: –NO2, –CN, –CHO, –⁠CO2R, –COR, –CO2H

5.3K
All meta-directing substituents are deactivating groups. These substituents withdraw electrons from the aromatic ring, making the ring less reactive toward electrophilic substitution. For example, the nitration of nitrobenzene is 100,000 times slower than that of benzene because of the deactivating effect of the nitro group. The first step in an electrophilic aromatic substitution is the addition of an electrophile to form a resonance-stabilized carbocation. The energy diagrams for...
5.3K
ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH301:11

ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH3

5.7K
All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...
5.7K
Structural Isomerism02:34

Structural Isomerism

19.1K
Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can...
19.1K
Nucleophilic Substitution Reactions02:34

Nucleophilic Substitution Reactions

15.9K
Historical perspective
In 1896, the German chemist Paul Walden discovered that he could interconvert pure enantiomeric (+) and (-) malic acids through a series of reactions. This conversion suggested the involvement of optical inversion during the substitution reaction. Further, in 1930, Sir Christopher Ingold described for the first time two different forms of nucleophilic substitution reactions, which are known as SN1 (nucleophilic substitution unimolecular) and SN2 (nucleophilic substitution...
15.9K
Diazonium Group Substitution: –OH and –H01:19

Diazonium Group Substitution: –OH and –H

2.7K
Nitrous acid, a weak acid, is prepared in situ via the reaction of sodium nitrite with a strong acid under cold conditions. This nitrous acid prepared in situ reacts with primary arylamines to form arenediazonium salts. Such reactions are known as diazotization reactions. As shown in Figure 1, the formation of arenediazonium salts begins with the decomposition of nitrous acid in an acidic solution to give nitrosonium ions.
2.7K

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相关实验视频

Updated: May 24, 2025

High-Contrast and Fast Photorheological Switching of a Twist-Bend Nematic Liquid Crystal
06:24

High-Contrast and Fast Photorheological Switching of a Twist-Bend Nematic Liquid Crystal

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在基于酸盐的非线性光学活性超分子多态之间切换.

Qiao Xia1, Xingxing Jiang2, Chunbo Jiang1

  • 1China-Australia Joint Research Center for Functional Molecular Materials, School of Chemical Science and Engineering, Tongji University, Shanghai, 200092, China.

Angewandte Chemie (International ed. in English)
|March 1, 2025
PubMed
概括
此摘要是机器生成的。

研究人员开发了一种新的pH调节策略,以合成三种非中心对称 (NCS) 酸盐超分子多态. 这种方法控制了二次键,使得这些先进材料具有量身定制的非线性光学 (NLO) 特性.

关键词:
亚酸盐是一种酸盐.非线性光学是一种非线性光学.阶段过渡 阶段过渡多态的多态体.结构与财产之间的关系.

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A 'Plug and Play' Method to Create Water-dispersible Nanoassemblies Containing an Amphiphilic Polymer, Organic Dyes and Upconverting Nanoparticles

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Patterning via Optical Saturable Transitions - Fabrication and Characterization
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Last Updated: May 24, 2025

High-Contrast and Fast Photorheological Switching of a Twist-Bend Nematic Liquid Crystal
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A 'Plug and Play' Method to Create Water-dispersible Nanoassemblies Containing an Amphiphilic Polymer, Organic Dyes and Upconverting Nanoparticles
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科学领域:

  • 材料科学 材料科学 材料科学
  • 晶体学 晶体学是指结晶学.
  • 非线性光学是非线性光学.

背景情况:

  • 合成非中心对称 (NCS) 二阶非线性光学 (NLO) 晶体,特别是转移稳定的多态晶体,由于复杂的相互作用,很难.
  • 控制晶体结构是实现所需NLO特性的关键.

研究的目的:

  • 报告使用pH调节二次键策略的三种酸盐超分子多态 (α,β,和γ相) 的首次合成.
  • 研究pH对二次键方向的影响及其对晶体包装和NLO特性的影响.

主要方法:

  • 使用pH调制策略组装 π 结合平面原始体 ([C2H5N4]和[NO3]).
  • 改变溶液的pH值,以控制二次键的方向,并影响晶格的包装.
  • 研究的多态转换 (例如,2Dα相转化为2Dβ相) 以及它们对NLO反应的影响.

主要成果:

  • 成功合成了具有不同NCS特征的三种酸盐超分子多态 (α-, β-, 和 γ-阶段).
  • 证明pH诱导的二次键变化决定了晶体包装,并可能导致不同的NLO特性.
  • 观察到与键层堆叠相关的α和β阶段明显的第二波生成 (SHG) 响应和双折.

结论:

  • 二次键相互作用对于形成罕见的酸盐超分子多态和控制它们的结构至关重要.
  • pH调节策略为开发具有定制光学特性的高性能NCS材料提供了一个新的范式.
  • 解的超分子多态过渡机制和NLO材料的结构-性质相关性.