Related Experiment Video
Updated: Sep 4, 2025
10:44
Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
Published on: April 19, 2019
11.0K
Persistent Radicals Derived from N-Heterocyclic Carbenes for Material Applications
Hayoung Song1, Ewa Pietrasiak1, Eunsung Lee1
1Department of Chemistry, Pohang University of Science and Technology. Pohang, 37673, Republic of Korea.
Accounts of Chemical Research
|July 18, 2022
Summary
N-Heterocyclic carbene (NHC)-derived radicals offer versatile applications, from targeted drug delivery and organic batteries to MRI contrast agents. These stable organic radicals demonstrate significant potential in advanced material science and medicine.
Area of Science:
- Materials Science
- Organic Chemistry
- Nanotechnology
- Biomedical Engineering
Background:
- Persistent radicals are key components for novel materials.
- N-Heterocyclic carbenes (NHCs) are effective in stabilizing radicals through spin delocalization and steric protection.
- NHC-stabilized radicals have shown promise in various applications over the past two decades.
Purpose of the Study:
- To describe recent advancements in developing NHC-derived persistent radicals.
- To explore prospective applications of these radicals in medicine and energy storage.
- To highlight the development of air- and physiologically stable organic radicals for flexible devices and MRI contrast agents.
Main Methods:
- Synthesis of NHC-nitric oxide (NHC-NO) radicals by trapping nitric oxide (NO) gas in NHCs.
- Loading NHC-NO radicals into biocompatible poly(ethylene glycol)-block-poly(caprolactone) (PEG-b-PCL) micelles for in vivo studies.
- Utilizing NHC-derived substituents to stabilize triazenyl and ferrocene derivatives for energy storage applications.
- Developing air- and physiologically stable organic radicals through coordination with tris(pentafluorophenyl)borane and reactions with oxalyl chloride.
Main Results:
- NHC-NO radicals were successfully delivered to tumors via micelles and released NO upon ultrasound irradiation.
- NHC-NO radicals served as precursors for generating other organic radicals like oxime ether and iminyl radicals.
- NHC-stabilized triazenyl radicals demonstrated potential as cathode active materials in batteries.
- NHC-supported ferrocene derivatives functioned as stable anolytes in nonaqueous all-organic redox flow batteries with high energy efficiency.
- Novel NHC-derived radical cations exhibited remarkable stability in air and aqueous/physiological conditions, suitable for MRI contrast agents.
Conclusions:
- NHC-derived persistent radicals are highly versatile, enabling applications in targeted drug delivery, energy storage, and medical imaging.
- The developed radicals exhibit excellent stability under various conditions, including air and physiological environments.
- This work provides a foundation for future development of stable NHC-derived organic radicals for advanced material science applications.
More Related Videos
12:19Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization
Published on: November 29, 2018
8.6K
19:58Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions
Published on: July 30, 2017
9.7K
Related Concept Videos
01:10Radical Reactivity: Steric Effects
2.0K
The presence of electron-donating, electron-withdrawing, or conjugating groups adjacent to a radical center, imparts electronic stabilization to the radicals. Examples of such electronically-stabilized radicals are triphenylmethyl, tetramethylpiperidine‐N‐oxide, and 2,2‐diphenyl‐1‐picrylhydrazyl. These radicals are remarkably stable and are known as persistent radicals. Some of the persistent radicals can even be isolated and purified.
Along with electronic...
Along with electronic...
2.0K
01:16Radical Reactivity: Nucleophilic Radicals
2.2K
Radicals adjacent to electron-donating groups are called nucleophilic radicals. These radicals readily react with electrophilic alkenes. The SOMO–LUMO interactions are the driving force for the reaction, where the high-energy SOMO of the electron-rich, nucleophilic radicals interacts with the low-energy LUMO of the electron-deficient, electrophilic alkenes. Such SOMO–LUMO interactions are the basis of reactive radical traps, affecting the selectivity in radical reactions. For...
2.2K
01:11Radical Reactivity: Overview
2.1K
Radicals, the highly reactive species, gain stability by undergoing three different reactions. The first reaction involves a radical-radical coupling, in which a radical combines with another radical, forming a spin‐paired molecule. The second reaction is between a radical and a spin‐paired molecule, generating a new radical and a new spin‐paired molecule. The third reaction is radical decomposition in a unimolecular reaction, forming a new radical and a spin‐paired...
2.1K
01:07Radicals: Electronic Structure and Geometry
4.2K
This lesson delves into the geometry of a radical, which is influenced by the electronic structure of the molecule. The principle is similar to that of a lone pair, where the unpaired electron influences the geometry at the radical center.
Accordingly, the structure of a trivalent radical lies between the geometries of carbocations and carbanions. An sp2-hybridized carbocation is trigonal planar, while an sp3-hybridized carbanion is trigonal pyramidal. Here, the difference in geometry is...
Accordingly, the structure of a trivalent radical lies between the geometries of carbocations and carbanions. An sp2-hybridized carbocation is trigonal planar, while an sp3-hybridized carbanion is trigonal pyramidal. Here, the difference in geometry is...
4.2K
01:18Aromatic Hydrocarbon Cations: Structural Overview
2.9K
Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon that consists of an odd number of carbon atoms and an intervening sp3 carbon in the ring. The three double bonds in the ring correspond to 6 π electrons, which is a Huckel number, and therefore satisfies the criteria of 4n + 2 π electrons. However, the intervening sp3 carbon disrupts the continuous overlap of p orbitals. As a result, cycloheptatriene is not aromatic.
Removing one hydrogen from the intervening CH2 group...
Removing one hydrogen from the intervening CH2 group...
2.9K
01:02Radical Reactivity: Electrophilic Radicals
2.0K
Radicals adjacent to electron‐withdrawing groups are called electrophilic radicals. These radicals readily react with nucleophilic alkenes. For example, the malonate radical, in which the radical center is flanked by two electron‐withdrawing groups, reacts readily with butyl vinyl ether, which consists of an electron‐donating oxygen substituent. The reaction between electrophilic malonate radical and nucleophilic vinyl ether is favored because the radical has a...
2.0K