Related Experiment Video
Updated: Jul 11, 2025
06:53
Author Spotlight: Magnetometric Characterization of Intermediates in the Solid-State Electrochemistry of Redox-Active Metal-Organic Frameworks
Published on: June 9, 2023
2.0K
Carbon-based Biradicals: Structural and Magnetic Switching
Yusuke Ishigaki1, Takashi Harimoto1, Takuya Shimajiri1,2
1Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan.
Chemical Reviews
|November 10, 2023
Summary
Sterically hindered C=C bonds in strained π-electron systems can twist into multiple shapes. These conformations switch and enable stimuli-responsive magnetic behavior in novel materials.
Area of Science:
- Organic Chemistry
- Materials Science
- Supramolecular Chemistry
Background:
- Sterically hindered C=C double bonds exhibit conformational flexibility, adopting bent or twisted geometries.
- Overcrowded ethylenes and anthraquinodimethanes can exist in multiple conformations, such as folded or twisted forms.
- These conformations are interconvertible upon application of external stimuli.
Purpose of the Study:
- To review recent advances in strained π-electron systems.
- To explore the factors influencing conformational interconversion and stimuli-responsive switching behavior.
- To highlight the development of carbon-based radical units for magnetic switching.
Main Methods:
- Analysis of conformational isomerism in strained π-electron systems.
- Investigation of stimuli-responsive properties.
- Structure-property relationship studies.
Main Results:
- The energy barrier for conformational interconversion is influenced by tricyclic skeletons and bulky substituents.
- A perpendicular biradical form can be adopted by incorporating stable carbon-based radical units.
- The stability of the perpendicular biradical form is enhanced by inserting 9,10-anthrylene units.
Conclusions:
- Strained π-electron systems offer tunable conformational dynamics.
- Stimuli-responsive magnetic switching is achievable through structural design.
- Understanding conformational control is key to developing advanced functional materials.
Related Concept Videos
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
4.1K
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...
4.1K
03:02Colors and Magnetism
11.7K
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
11.7K
00:47Radical Formation: Addition
1.7K
Radicals can be formed by adding a radical to a spin-paired molecule. This is typically observed with unsaturated species, where the addition of a radical across the π bond leads to the production of a new radical by dissolving the π bond. For example, the addition of a Br radical to an alkene yields a carbon-centered radical.
Similar to charge conservation in chemical reactions, spin conservation is implicit for radical reactions. Accordingly, the product formed must possess an...
Similar to charge conservation in chemical reactions, spin conservation is implicit for radical reactions. Accordingly, the product formed must possess an...
1.7K
01:17Electron Paramagnetic Resonance (EPR) Spectroscopy: Organic Radicals
2.6K
Ideally, an unpaired electron shows a single peak in the EPR spectrum due to the transition between the two spin energy states. However, coupling interactions can occur between the spins of the unpaired electron and any neighboring spin-active nuclei. This hyperfine coupling results in hyperfine splitting, where the EPR signal is split into multiplets. The signals split into 2nI + 1 peaks, where n is the number of equivalent nuclei and I is the nuclear spin. These splitting patterns provide...
2.6K
01:27π Electron Effects on Chemical Shift: Overview
1.1K
An applied magnetic field causes loosely bound π-electrons in organic molecules to circulate, producing a local or induced diamagnetic field over a large spatial volume. As the molecules tumble in solution, the field generated by π-electrons in spherical substituents results in a zero net field. However, the net field generated by π-electrons in non-spherical substituents is not zero. The effect of this induced field depends on the orientation of the molecule with respect to B0,...
1.1K