Related Experiment Video
Updated: Mar 26, 2026
11:44
Using Cyclic Voltammetry, UV-Vis-NIR, and EPR Spectroelectrochemistry to Analyze Organic Compounds
Published on: October 18, 2018
27.8K
Exchange Coupling Inversion in a High-Spin Organic Triradical Molecule.
R Gaudenzi1, E Burzurí1, D Reta2
1Kavli Institute of Nanoscience, Delft University of Technology , 2600 GA, Delft, The Netherlands.
Nano Letters
|February 11, 2016
Summary
We discovered that structural changes can flip the magnetic coupling in organic molecules, turning a robust high-spin state into a low-spin one. This allows for electrical control of magnetic states in molecular nanodevices.
Area of Science:
- Molecular magnetism
- Organic electronics
- Nanoscale science
Background:
- Magnetic properties of nanoscale systems depend heavily on their local environment.
- Exchange interactions in adatoms and layered structures are influenced by lattice positions and layer thickness.
Purpose of the Study:
- To investigate the magnetic exchange coupling in an organic triradical molecule within a three-terminal device.
- To explore the tunability of magnetic states in organic molecule-based nanodevices.
Main Methods:
- Fabrication of a three-terminal device embedding an organic triradical molecule.
- Characterization of sample-dependent magnetic exchange coupling.
- Investigation of in situ electric field effects on magnetic coupling.
Main Results:
- Observed a sample-dependent sign inversion of magnetic exchange coupling in the organic triradical.
- Demonstrated a ferro-to-antiferromagnetic transition leading to a high-to-low spin ground state change.
- Achieved in situ electric tunability of the exchange coupling via a gate electrode.
Conclusions:
- Structural distortions can alter magnetic coupling and spin states in organic molecules.
- Organic molecule-based nanodevices offer tunable magnetic states through electrical gating.
- This work provides a pathway for controlled magnetic state reversal in molecular nanodevices.
Related Concept Videos
01:33Radical Reactivity: Intramolecular vs Intermolecular
2.3K
Radical reactions can occur either intermolecularly or intramolecularly. In an intermolecular radical reaction, a nucleophilic radical adds to an electrophilic alkene or vice versa. In such reactions, the radical and generally the alkene, which is also called the radical trap, are two different molecules. Additionally, for such intermolecular reactions to occur, the radical trap must be active, present in an excess concentration, and the radical starting material must have a weak...
2.3K
01:17Electron Paramagnetic Resonance (EPR) Spectroscopy: Organic Radicals
3.7K
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...
3.7K
01:11Radical Reactivity: Overview
3.0K
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...
3.0K
01:22Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)
1.7K
Vicinal or three-bond coupling is commonly observed between protons attached to adjacent carbons. Here, nuclear spin information is primarily transferred via electron spin interactions between adjacent C‑H bond orbitals. This generally favors the antiparallel arrangement of spins, so 3J values are usually positive.
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the involved orbitals. The...
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the involved orbitals. The...
1.7K
01:20Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)
1.9K
Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
1.9K
01:26Photochemical Electrocyclic Reactions: Stereochemistry
2.4K
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation
2.4K