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相关概念视频

Complexation Equilibria: The Chelate Effect01:19

Complexation Equilibria: The Chelate Effect

1.6K
In complexation reactions, metal atoms or cations interact with ligands to form donor-acceptor adducts called metal complexes. Ligands that bind through one donor site are monodentate, ligands with two donor sites are bidentate, and those with more than two donor sites are polydentate ligands. For example, ethylene diamine is a bidentate ligand that binds through two nitrogen donor atoms, forming a five-membered ring. EDTA is a polydentate ligand that binds through four oxygen and two nitrogen...
1.6K
Complexometric Titration: Ligands00:43

Complexometric Titration: Ligands

2.7K
Different monodentate and polydentate ligands are used as complexing agents in complexometric titration reactions. The formation of complexes by mono- and bidentate ligands involves two or more intermediate steps, limiting their use as complexing agents. In comparison, polydentate ligands can form complexes with metal ions in a single-step process, facilitating sharper end points. This means polydentate ligands, such as amino carboxylic acid derivatives, are most commonly employed in...
2.7K
Extraction: Advanced Methods00:56

Extraction: Advanced Methods

1.3K
Metal ions can be separated from one another by complexation with organic ligands–the chelating agent– to form uncharged chelates. Here, the chelating agent must contain hydrophobic groups and behave as a weak acid, losing a proton to bind with the metal. Since most organic ligands used in this process are insoluble or undergo oxidation in the aqueous phase, the chelating agent is initially added to the organic phase and extracted into the aqueous phase. The metal-ligand complex is...
1.3K
Metal-Ligand Bonds02:51

Metal-Ligand Bonds

25.9K
The hemoglobin in the blood, the chlorophyll in green plants, vitamin B-12, and the catalyst used in the manufacture of polyethylene all contain coordination compounds. Ions of the metals, especially the transition metals, are likely to form complexes.
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
25.9K
Complexation Equilibria: Factors Influencing Stability of Complexes01:09

Complexation Equilibria: Factors Influencing Stability of Complexes

994
In complexation reactions, metal cations are the electron pair acceptors, and the ligands are the electron pair donors. The stability of the metal complexes depends primarily on the complexing ability of the central metal ion and the nature of the ligands. Generally, the complexing ability of the metal ion depends on the size and charge of the ion. As the metal ion size increases, the stability of the metal complexes decreases, provided that the valency of the metal ion and the ligands remain...
994
EDTA: Chemistry and Properties01:22

EDTA: Chemistry and Properties

4.1K
Polydentate ligands are most widely used in complexometric titrations because they form more stable complexes with the metal ions than mono- or bidentate ligands due to the chelate effect. Examples of polydentate ligands are ethylenediaminetetraacetic acid (EDTA), crown ethers, and cryptands. The most important feature of optimal polydentate ligands is the ability to form 1:1 complexes in a single-step process. Amino carboxylic acid derivatives are frequently used as complexing agents. EDTA is...
4.1K

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相关实验视频

Updated: Apr 16, 2026

Preparation of Polyoxometalate-based Photo-responsive Membranes for the Photo-activation of Manganese Oxide Catalysts
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聚氧甲酸盐与环极素的复合.

Yilei Wu1, Rufei Shi1,2, Yi-Lin Wu1

  • 1†Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States.

Journal of the American Chemical Society
|March 11, 2015
PubMed
概括

这项研究表明,多氧甲酸盐 (POMs) 在循环脱素 (CDs) 中出现了意想不到的复杂化,形成了稳定的有机-无机混合材料. 这些POM-CD复合体在溶液中表现出独特的结构和保存的氧化还原特性,为POM功能化开辟了道路.

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Heterogeneous Removal of Water-Soluble Ruthenium Olefin Metathesis Catalyst from Aqueous Media Via Host-Guest Interaction
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科学领域:

  • 超分子化学 超分子化学
  • 材料科学 材料科学 材料科学
  • 无机化学 无机化学

背景情况:

  • 在疏水性宿主中复合水友性宿主通常具有挑战性.
  • 聚氧甲酸盐 (POMs) 是多功能无机集群,具有多样化的应用.
  • 环极素 (CDs) 是超分子化学中成熟的宿主分子.

研究的目的:

  • 为了研究一个多氧甲酸盐 ([PMo12O40](3-)) 与玛-和β-环极素 (CDs) 的复杂化.
  • 描述由此产生的有机-无机杂交复合物的结构和特性.
  • 探索宿主-客人化学对POMs功能化的潜力.

主要方法:

  • 合成2:1的环极-POM复合物 ([La(H2O) 9{[PMo12O40][γ-CD]2}和[La(H2O) 9{[PMo12O40][β-CD]2}). 这两种复合物中,一种是环极,另一种是环极.
  • 使用单晶X射线衍射进行结构分析.
  • 通过NMR光谱学,X射线散射和质谱学进行溶液行为调查.
  • 电化学研究以评估氧化还原特性.

主要成果:

  • 在固态中形成两个稳定的2:1有机-无机混合复合物.
  • 单晶X射线衍射揭示了一个类似三明治的结构,通过C-H··OMo相互作用,POM被两个CD封装在一起.
  • 复合体通过O-H··O相互作用在固体状态中形成1D柱状超结构.
  • 在水溶液中,有纳米封闭效应和缓慢的颜色变化的证据.
  • 封装POM在很大程度上保留了它们在溶液中的氧化还原特性.

结论:

  • 在疏水性CD中证明了水友性POM在水友性CD中成功复合,挑战了以前的假设.
  • 超分子互补性使得形成具有功能化潜力的精确定义的混合材料成为可能.
  • 主客化学为修改POM属性和应用提供了一种温和的方法.