Related Experiment Video
Updated: Jun 12, 2026
10:16
Electroactive Polymer Nanoparticles Exhibiting Photothermal Properties
Published on: January 8, 2016
Low-energy electron collisions with pyrrole
Eliane M de Oliveira1, Marco A P Lima, Márcio H F Bettega
1Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, 13083-970 Campinas, Sao Paulo, Brazil.
The Journal of Chemical Physics
|June 3, 2010
Summary
Low-energy electron scattering reveals shape resonances in pyrrole, crucial for understanding its photostability and dissociative electron attachment (DEA) pathways. These findings link pyrrole
Area of Science:
- Theoretical Chemistry
- Physical Chemistry
- Quantum Mechanics
Background:
- Pyrrole is a fundamental heterocyclic aromatic compound with significant biological relevance.
- Understanding electron-molecule interactions in pyrrole is key to elucidating its photochemical properties and potential damage mechanisms in biological systems.
- Previous studies on isoelectronic molecules like furan provide a basis for comparison.
Purpose of the Study:
- To calculate cross sections for low-energy elastic electron scattering by pyrrole.
- To identify and characterize shape resonances in pyrrole.
- To investigate the relationship between electron attachment, molecular resonances, and dissociative electron attachment (DEA) pathways.
Main Methods:
- Schwinger multichannel method (SMC) implemented with pseudopotentials.
- Calculation of elastic electron scattering cross sections.
- Analysis of resonance symmetries (π* and σ*) and localization.
Main Results:
- Identified π* shape resonances in B(1) and A(2) symmetries and two σ* resonances in A(1) symmetry.
- The lowest-lying σ* anion is localized on the N-H bond, suggesting a dissociation coordinate.
- Observed overlap between σ*(NH) and π* resonances, indicating potential direct and indirect dissociation pathways.
Conclusions:
- Pyrrole exhibits distinct resonance structures influencing its electron interaction dynamics.
- The N-H σ* resonance is linked to dissociation pathways, similar to those in alcohols and acids.
- Pyrrole serves as a suitable model for studying DEA to DNA bases, connecting photostability mechanisms with electron attachment processes.
More Related Videos
![[(DPEPhos)(bcp)Cu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F59739.jpg&w=3840&q=50)
Related Concept Videos
01:14π Electron Effects on Chemical Shift: Aromatic and Antiaromatic Compounds
In aromatic compounds, such as benzene, the circulation of (4n + 2) π-electrons sets up a diamagnetic or diatropic ring current around the perimeter of the molecule. This current induces a magnetic field that opposes the external field inside the ring and reinforces it on the outside. The protons in benzene are deshielded and exhibit high chemical shifts in the range 6.5–8.5 ppm. The shielding effect at the center of the ring is evident in complex aromatic molecules, such as annulenes. In...
01:25Basicity of Heterocyclic Aromatic Amines
Heterocyclic amines, where the N atom is a part of an alicyclic system, are similar in basicity to alkylamines. Interestingly, the heterocyclic amine having a nitrogen atom as part of an aromatic ring has much less basicity than its corresponding alicyclic counterpart. For this reason, as presented in Figure 1, piperidine (pKb = 2.8) is significantly more basic than pyridine (pKb = 8.8).
01:27π Electron Effects on Chemical Shift: Overview
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, resulting in...
01:17Electron Paramagnetic Resonance (EPR) Spectroscopy: Organic Radicals
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...
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
01:26Photochemical Electrocyclic Reactions: Stereochemistry
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