Video Experimental Relacionado

Updated: Jul 23, 2026

In situ FTIR Spectroscopy as a Tool for Investigation of Gas/Solid Interaction: Water-Enhanced CO2 Adsorption in UiO-66 Metal-Organic Framework

In situ FTIR Spectroscopy as a Tool for Investigation of Gas/Solid Interaction: Water-Enhanced CO₂ Adsorption in UiO-66 Metal-Organic Framework

Published on: February 1, 2020

Efecto del oxígeno molecular en los espectros de RMN 29Si MAS de temperatura variable de los complejos de

Colin A Fyfe¹, Darren H Brouwer

¹Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia, Canada V6T 1Z1. fyfe@chem.ubc.ca

Journal of the American Chemical Society

|February 5, 2004

Resumen

El oxígeno molecular paramagnético amplía los espectros de RMN 29Si MAS en complejos de zeolita-sorbato. La eliminación de oxígeno con gas de nitrógeno mejora significativamente la resolución espectral, ayudando a la determinación de la estructura.

Área de la Ciencia:

Ciencia de los materiales Ciencia de los materiales.
Química del estado sólido.
Espectroscopia de resonancia magnética nuclear Espectroscopia de resonancia magnética nuclear Espectroscopia de resonancia magnética nuclear Espectroscopia de resonancia magnética nuclear

Sus antecedentes:

La RMN en estado sólido es crucial para determinar la estructura de los complejos anfitrión-invitado de zeolita-sorbato.
Las bajas temperaturas a menudo conducen a un espectro de RMN 29Si MAS ampliado, lo que dificulta el análisis estructural detallado.

Objetivo del estudio:

Para investigar la causa de la ampliación de la línea en los espectros de RMN 29Si MAS de complejos de zeolita-sorbato a bajas temperaturas.
Identificar métodos para mejorar la resolución espectral para una determinación precisa de la estructura.

Principales métodos:

Espectroscopia de resonancia magnética nuclear (RMN) de estado sólido 29Si girando ángulo mágico (MAS).Espectroscopia de resonancia magnética nuclear (RMN).
Estudios de RMN de temperatura variable para analizar los tiempos de relajación de 29Si T1 y T2.
Tratamiento de la muestra que implica purgar con gas nitrógeno para eliminar el oxígeno.

Principales resultados:

La ampliación del pico 29Si está directamente relacionada con los tiempos de relajación 29Si T2.
El oxígeno molecular paramagnético dentro de los canales de zeolita se identifica como la principal fuente de relajación y ampliación de la línea.
La purga de gas de nitrógeno mejoró dramáticamente la resolución espectral para el complejo p-dibromobenzeno/ZSM-5.
El análisis de los tiempos de relajación de 29Si T1 indicó la localización de oxígeno en los canales en zigzag de ZSM-5.

Conclusiones:

El oxígeno molecular tiene un impacto significativo en la calidad de los espectros de RMN en estado sólido para complejos de zeolita-sorbato.
La eliminación de oxígeno es una estrategia efectiva para mejorar la resolución espectral y permitir una determinación precisa de la estructura.
La localización de oxígeno observada sugiere que el p-dibromobenzeno reside en las intersecciones de los canales ZSM-5.

Más Videos Relacionados

High-Temperature and High-Pressure In situ Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy

High-Temperature and High-Pressure In situ Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy

Published on: October 9, 2020

Line Shape Analysis of Dynamic NMR Spectra for Characterizing Coordination Sphere Rearrangements at a Chiral Rhenium Polyhydride Complex

Line Shape Analysis of Dynamic NMR Spectra for Characterizing Coordination Sphere Rearrangements at a Chiral Rhenium Polyhydride Complex

Published on: July 27, 2022

Videos de Conceptos Relacionados

¹H NMR: Complex Splitting

¹H 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.

¹H NMR of Conformationally Flexible Molecules: Temporal Resolution

¹H NMR of Conformationally Flexible Molecules: Temporal Resolution

At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...

IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations

IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations

Identical bonds within a polyatomic group can stretch symmetrically (in-phase) or asymmetrically (out-of-phase). Similar to hydrogen bonding, these vibrations also influence the shape of the IR peak. Generally, asymmetric stretching frequencies are higher than symmetric stretching frequencies. For example, primary amines exhibit two distinct IR peaks between 3300–3500 cm−1 corresponding to the symmetric and asymmetric N-H stretching, while secondary amines exhibit a single stretching vibration...

NMR Spectroscopy of Aromatic Compounds

NMR Spectroscopy of Aromatic Compounds

Aromatic compounds can be identified or analyzed using proton NMR and carbon‐13 NMR. Typically, aromatic hydrogens or hydrogens directly bonded to the aromatic rings are strongly deshielded by the aromatic ring current. Therefore, they absorb in the range of 6.5–8.0 ppm in proton NMR spectra. For instance, aromatic hydrogens directly bonded to the benzene ring absorb at 7.3 ppm. However, aromatic hydrogens of larger rings absorb farther upfield or downfield than the ideal range. Consider...

¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR

¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR

The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.

Atomic Spectroscopy: Effects of Temperature

Atomic Spectroscopy: Effects of Temperature

Atomization, converting samples into gas-phase atoms and ions, is essential for atomic spectroscopy. The flame temperature required for atomization affects the efficiency of the atomic spectroscopic methods by increasing the atomization efficiency and the relative population of the excited and ground states.
At thermal equilibrium, the relative populations of excited and ground state atoms can be estimated using the Maxwell–Boltzmann distribution. For example, an increase in temperature from...