Related Experiment Video
Updated: May 19, 2026
08:44
Measurements of Long-range Electronic Correlations During Femtosecond Diffraction Experiments Performed on Nanocrystals of Buckminsterfullerene
Published on: August 22, 2017
Electronic excitations of C60 aggregates
A L Montero-Alejo1, E Menéndez-Proupin, M E Fuentes
1Laboratorio de Química Computacional y Teórica, Facultad de Química, Universidad de la Habana, 10400 Havana, Cuba. analilian.montero@fq.uh.cu
Physical Chemistry Chemical Physics : PCCP
|August 15, 2012
Summary
This study explores fullerene C(60) clusters, revealing how aggregation affects their excitation properties. Clustering introduces new spectral peaks and alters UV absorption, with electron transitions depending on cluster size.
Area of Science:
- * Computational chemistry and condensed matter physics.
- * Investigating the electronic and optical properties of fullerene materials.
Background:
- * Fullerenes, particularly C(60), are carbon allotropes with unique electronic properties.
- * Understanding how C(60) molecules interact and aggregate is crucial for their application in materials science.
- * Previous studies have explored C(60) properties, but the impact of controlled aggregation on excitation spectra requires further investigation.
Purpose of the Study:
- * To investigate the excitation properties of isolated C(60) and aggregated (C(60))(N) clusters.
- * To model the effects of fullerene aggregation on electronic and absorption spectra.
- * To analyze the influence of cluster size and inter-fullerene distance on excitation characteristics.
Main Methods:
- * Utilized the Complete Neglect of Differential Overlap ( a priori parameterized and self-consistent Hamiltonian) method.
- * Employed the configuration interaction of singles (CIS) procedure for electron excitation calculations.
- * Modeled (C(60))(N) clusters using geometry derived from the fullerene face-centered cubic crystal structure.
Main Results:
- * The chosen computational method accurately reproduces experimental excitation data for isolated C(60).
- * Aggregation effects were observed as new peaks at the low-energy edge of the absorption spectrum.
- * Small increases in bandwidths were noted in the strong ultraviolet absorption bands for clusters.
- * Analysis of dimer models showed dependence of spectral features on inter-fullerene distance.
- * Calculated density of states indicated size-dependent electron transitions in fullerene clusters.
Conclusions:
- * Fullerene aggregation significantly influences excitation properties, introducing new spectral features.
- * The size of C(60) clusters plays a key role in determining electron transition possibilities.
- * The computational approach provides valuable insights into the electronic behavior of aggregated fullerenes.
Related Concept Videos
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...
01:26Photochemical 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
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.
01:14π 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...
01:17Electron 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...
02:10Carbocations
Carbocations are one of the reaction intermediates formed during several nucleophilic substitutions or elimination reactions. A carbocation is an electron-deficient species with the central carbon atom having six electrons and three bonded atoms. The central carbon in a carbocation is sp2 hybridized with trigonal planar geometry. It has an empty p orbital perpendicular to the plane of the structure that can accept electrons. Thus, carbocations act as strong electrophiles and may react with any...