Video Experimental Relacionado
Updated: Jul 18, 2026
07:44
Resonance Raman Spectroscopy of Extreme Nanowires and Other 1D Systems
Published on: April 28, 2016
Artefactos en los espectros de resonancia paramagnética de electrones de los iones fullereno C60: inevitable impureza
Parimal Paul1, Kee-Chan Kim, Dayong Sun
1Department of Chemistry, University of California, Riverside, California 92521-0403, USA.
Journal of the American Chemical Society
|April 19, 2002
Resumen
Se reinterpretan los estudios de resonancia paramagnética de electrones (EPR) de iones de fuleruro y C60 sólido. Las impurezas como C120O y la reducción incompleta comprometen los espectros anteriores, lo que lleva a nuevas asignaciones para las señales EPR en especies C60 y C120O.
Área de la Ciencia:
- Química del estado sólido y espectroscopia.
- Ciencia de materiales de los fullerenos y sus derivados.
Sus antecedentes:
- La espectroscopia de resonancia paramagnética de electrones (EPR) es crucial para caracterizar especies paramagnéticas como los iones fulleruro.
- Estudios previos de EPR de C60n- (n=2,3) y C60 sólido se han complicado por impurezas y reducción incompleta.
- C120O es una impureza común en el C60, que afecta significativamente los espectros EPR.
Objetivo del estudio:
- Reevaluar y reinterpretar los datos EPR existentes para los iones C60n-fulleruro y el sólido C60.
- Para identificar las fuentes de señales EPR previamente mal asignadas.
- Establecer espectros EPR auténticos para C60- y C60- bajo condiciones controladas.
Principales métodos:
- Reinterpretación de los datos espectrales EPR existentes de C60n- (n=2,3) y C60 sólido.
- Análisis de las señales EPR atribuidas a las especies C120On-, teniendo en cuenta los diferentes niveles de reducción y presencia de impurezas.
- Preparación de muestras de C60 altamente purificadas en condiciones estrictamente anaerobias para la adquisición espectral auténtica.
Principales resultados:
- Las señales centrales de anchura de línea estrecha en espectros de fulleruroides se atribuyen a C120On- (n = impar).
- Las señales tripletas axiales en los espectros C60(2-) se reasignan a C120On- (n=2 o 4), con valores D que apoyan a C120O.
- Se sugiere que la señal EPR en el C60 expuesto al aire se origina en diradicals con puentes de peróxido (*C60-O-O-C60*) o productos de descomposición, no en C60*+.
Conclusiones:
- La presencia de la impureza C120O tiene un impacto significativo en los espectros EPR de los fuleruros y C60.
- El ion C60(2-) es EPR-silencioso, y sus señales previamente asignadas pertenecen a la especie C120On-.
- Se pueden obtener espectros EPR auténticos de C60- y C60(3-) a partir de muestras altamente purificadas y preparadas anaeróbicamente.
Más Videos Relacionados
07:51Combining Raman Imaging and Multivariate Analysis to Visualize Lignin, Cellulose, and Hemicellulose in the Plant Cell Wall
Published on: June 10, 2017
08:44Measurements of Long-range Electronic Correlations During Femtosecond Diffraction Experiments Performed on Nanocrystals of Buckminsterfullerene
Published on: August 22, 2017
Videos de Conceptos Relacionados
01:13¹H NMR: Complex Splitting
A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
01:10Carbon-13 (¹³C) NMR: Overview
Carbon-13 is a naturally occurring NMR-active isotope of carbon with a low natural abundance of 1.1%. In contrast, carbon-12 is the most abundant isotope of carbon with zero nuclear spin. Therefore, it is NMR inactive. The gyromagnetic ratio of carbon-13 is smaller than that of protons. As a result, carbon-13 resonance is about 6000 times weaker than proton resonance. For a given magnetic field strength, the resonance frequency of carbon-13 is about one-fourth of the resonance frequency for...
01:15NMR Spectroscopy: Chemical Shift Overview
The position of the absorption signal of a sample is reported relative to the position of the signal of tetramethylsilane (TMS), which is added as an internal reference while recording spectra. The difference between the absorption frequencies of the sample and TMS (in Hz) is divided by the spectrometer operating frequency (in MHz) to obtain a dimensionless quantity called the chemical shift. It is reported on the δ (delta) scale and expressed in parts per million.
For instance, the proton...
For instance, the proton...
01:08NMR Spectroscopy: Spin–Spin Coupling
The spin state of an NMR-active nucleus can have a slight effect on its immediate electronic environment. This effect propagates through the intervening bonds and affects the electronic environments of NMR-active nuclei up to three bonds away; occasionally, even farther. This phenomenon is called spin–spin coupling or J-coupling. Coupling interactions are mutual and result in small changes in the absorption frequencies of both nuclei involved. While nuclei of the same element are involved in...
01:04¹³C NMR: ¹H–¹³C Decoupling
The probability of having two carbon-13 atoms next to each other is negligible because of the low natural abundance of carbon-13. Consequently, peak splitting due to carbon-carbon spin-spin coupling is not observed in spectra. However, protons up to three sigma bonds away split the carbon signal according to the n+1 rule, resulting in complicated spectra.
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
01:16UV–Vis Spectroscopy: Molecular Electronic Transitions
In Ultraviolet–Visible (UV–Vis) spectroscopy, the absorption of electromagnetic radiation is used to probe the electronic structure of molecules. This technique provides insights into molecular electronic transitions, particularly the movement of electrons between different molecular orbitals. Radiation is absorbed if the energy of the electromagnetic radiation passing through the molecule is precisely equal to the energy difference between the excited and ground states. During this process,...