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Related Concept Videos

Structural Isomerism02:34

Structural Isomerism

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 be...
Stereoisomerism02:52

Stereoisomerism

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...
Structure of Amines01:19

Structure of Amines

The hybridized nitrogen atom in amines possesses a lone pair of electrons and is bound to three substituents with a bond angle of around 108°, which is less than the tetrahedral angle of 109.5°. However, the C–N–H bond angle is slightly larger at 112°, with a carbon–nitrogen bond length of 147 pm. This carbon–nitrogen bond length of of amines is longer than the carbon–oxygen bond of alcohols (143 pm) but shorter than alkanes’ carbon–carbon bond (154 pm). These aspects are illustrated in Figure...
Variables Affecting Phosphorescence and Fluorescence01:26

Variables Affecting Phosphorescence and Fluorescence

Fluorescence and phosphorescence are essential phenomena in fields like analytical chemistry, biological imaging, and materials science, where they detect molecular properties and visualize cellular structures. Understanding the variables that influence these luminescent behaviors is crucial for maximizing accuracy and efficiency in their applications. These variables can broadly be grouped into chemical structure, solvent properties, and external conditions, each playing a distinct role in...
Valence Bond Theory02:42

Valence Bond Theory

Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
Cycloaddition Reactions: MO Requirements for Photochemical Activation01:12

Cycloaddition Reactions: MO Requirements for Photochemical Activation

Some cycloaddition reactions are activated by heat, while others are initiated by light. For example, a [2 + 2] cycloaddition between two ethylene molecules occurs only in the presence of light. It is photochemically allowed but thermally forbidden.

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Related Experiment Video

Updated: Jun 10, 2026

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach
14:11

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach

Published on: June 10, 2021

Imine Linkage Isomerism in Layer-Entangled Three-Dimensional Covalent Organic Frameworks Modulates Fluorescent

Yuanpeng Cheng1, Yongyong Wang1, Lin Li1,2

  • 1College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, China.

Angewandte Chemie (International Ed. in English)
|June 8, 2026
PubMed
Summary

Investigating linkage isomerism in 3D covalent organic frameworks (COFs) revealed significant differences in optoelectronic properties. One isomer demonstrated highly sensitive fluorescent detection of 2,4,6-trinitrophenol (TNP) in water.

Keywords:
covalent organic frameworksfluorescent sensingimine linkage isomerismlayer‐entangled

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Hyperspectral Imaging as a Tool to Study Optical Anisotropy in Lanthanide-Based Molecular Single Crystals
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Hyperspectral Imaging as a Tool to Study Optical Anisotropy in Lanthanide-Based Molecular Single Crystals

Published on: April 14, 2020

Related Experiment Videos

Last Updated: Jun 10, 2026

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach
14:11

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach

Published on: June 10, 2021

Hyperspectral Imaging as a Tool to Study Optical Anisotropy in Lanthanide-Based Molecular Single Crystals
07:24

Hyperspectral Imaging as a Tool to Study Optical Anisotropy in Lanthanide-Based Molecular Single Crystals

Published on: April 14, 2020

Area of Science:

  • Materials Science
  • Chemistry
  • Nanotechnology

Background:

  • Three-dimensional covalent organic frameworks (3D COFs) with entangled layers are rare.
  • The impact of linkage structure variations in these 3D COFs is not well understood.

Purpose of the Study:

  • To explore the effect of imine bond orientation on the properties of layer-entangled 3D COFs.
  • To investigate how subtle structural changes influence optoelectronic properties and fluorescent sensing capabilities.

Main Methods:

  • Synthesized and characterized a pair of linkage-isomeric 3D COFs with opposite imine bond orientations.
  • Evaluated the optoelectronic properties and fluorescent sensing performance of both COFs.

Main Results:

  • Despite similar composition and porosity, the two COFs exhibited distinct optoelectronic properties and sensing behaviors.
  • 3D-An-CN-COF showed superior sensitivity for 2,4,6-trinitrophenol (TNP) detection (limit of detection: 9.5 nmol L⁻¹).

Conclusions:

  • Imine linkage isomerism is a key factor in tuning the properties of layer-entangled 3D COFs.
  • This finding provides insights for designing advanced fluorescent sensing materials.