Video Experimental Relacionado

Updated: Feb 27, 2026

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

Predicción de los tensores de blindaje químico de resonancia magnética nuclear 9Be utilizando la teoría funcional de

Paul G Plieger¹, Kevin D John, Timothy S Keizer

¹Chemistry Division, MS J582, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.

Journal of the American Chemical Society

|November 4, 2004

Resumen

Este estudio optimiza las estructuras complejas del berilio y calcula el escudo magnético (9) Be. El método GIAO predice con precisión los desplazamientos químicos de la RMN del berilio, lo que sugiere un nuevo estándar para los disolventes no acuosos.

Área de la Ciencia:

Química computacional es la química computacional.
Espectroscopia de Resonancia Magnética Nuclear (RMN) Espectroscopia de Resonancia Magnética Nuclear (RMN) Espectroscopia de Resonancia Magnética Nuclear (RMN) Espectroscopia de Resonancia Magnética Nuclear (RMN) Espectroscopia de Resonancia Magnética Nuclear (RMN) Espectroscopia de Resonancia Magnética Nuclear (RMN) Espectroscopia de Resonancia Magnética Nuclear (RMN) Espectroscopia de Resonancia Magnética Nuclear (RMN) Espectroscopia de Resonancia Magnética Nuclear (RMN) Espectroscopia de Resonancia Magnética Nuclear (RMN) Espectroscopia de Resonancia Magnética Nuclear (RMN) Espectroscopia de Resonancia Magnética Nuclear (RMN)
Química Inorgánica La Química Inorgánica es la química inorgánica.

Sus antecedentes:

La predicción precisa de los cambios químicos de la resonancia magnética nuclear (RMN) es crucial para caracterizar las estructuras moleculares.
La espectroscopia de RMN de berilio-9 ((9) Be proporciona información valiosa sobre el entorno electrónico de los átomos de berilio en los complejos.
Los métodos teóricos existentes para predecir (9) Be desplazamientos químicos de RMN requieren validación y refinamiento.

Objetivo del estudio:

Para optimizar las estructuras de los complejos que contienen berilio utilizando la teoría funcional de la densidad (DFT).
Para calcular (9) los valores de blindaje magnético de Be y los desplazamientos químicos de RMN utilizando el método GIAO (Orbital Atómico Inclusivo).
Evaluar el rendimiento de diferentes métodos computacionales de RMN y proponer un nuevo estándar para (9) Be RMN en disolventes no acuosos.

Principales métodos:

Cálculos químicos cuánticos que emplean el funcional B3LYP con conjuntos de bases 6-31G(d) y 6-311+G(2d,p).
Optimización de la geometría de los complejos de berilio.
Cálculo de las constantes de blindaje magnético (9) Be utilizando el método GIAO y comparación con otros métodos de RMN (SGO, IGAIM, CSGT).

Principales resultados:

Se obtuvieron estructuras optimizadas de varios complejos de berilio.
Los desplazamientos químicos calculados (9)Be utilizando el método GIAO mostraron una excelente concordancia con los datos experimentales.
El método GIAO superó a otros enfoques computacionales de RMN probados (SGO, IGAIM, CSGT) en el nivel teórico empleado.

Conclusiones:

El método GIAO, combinado con el nivel teórico B3LYP/6-311+G(2d,p), es una herramienta confiable para predecir los desplazamientos químicos de la RMN (9)Be.
El enfoque teórico validado se puede utilizar para predecir cambios químicos para complejos no caracterizados e investigar señales de RMN inusuales.
Se ha propuesto un nuevo estándar para la espectroscopia de RMN (9)Be en disolventes no acuosos basado en los hallazgos computacionales.

Más Videos Relacionados

Vibrational Spectra of a N719-Chromophore/Titania Interface from Empirical-Potential Molecular-Dynamics Simulation, Solvated by a Room Temperature Ionic Liquid

Vibrational Spectra of a N719-Chromophore/Titania Interface from Empirical-Potential Molecular-Dynamics Simulation, Solvated by a Room Temperature Ionic Liquid

Published on: January 25, 2020

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy

Published on: September 17, 2017

Videos de Conceptos Relacionados

Diamagnetic Shielding of Nuclei: Local Diamagnetic Current

Diamagnetic Shielding of Nuclei: Local Diamagnetic Current

An applied magnetic field causes the electrons present in the molecule to circulate, setting up a local diamagnetic current within the molecule. The local diamagnetic current arising from circulating sigma-bonding electrons induces a magnetic field, Blocal that opposes the applied magnetic field, B0. The effective magnetic field experienced by these nuclei is given by the difference between the applied and local magnetic fields in a phenomenon called local diamagnetic shielding. Essentially,...

π Electron Effects on Chemical Shift: Overview

π 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,...

π Electron Effects on Chemical Shift: Aromatic and Antiaromatic Compounds

π 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...

Crystal Field Theory - Octahedral Complexes

Crystal Field Theory - Octahedral Complexes

Crystal Field Theory
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...

NMR Spectroscopy: Chemical Shift Overview

NMR 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...

Inductive Effects on Chemical Shift: Overview

Inductive Effects on Chemical Shift: Overview

The protons in unsubstituted alkanes are strongly shielded with chemical shifts below 1.8 ppm. Methine, methylene, and methyl protons appear at approximately 1.7, 1.2 and 0.7 ppm, while the proton signal from methane appears at 0.23 ppm. An electronegative substituent, such as chlorine, withdraws the electron density from the protons, increasing their chemical shift. Progressive substitution of the hydrogens in methane by chlorine shifts the proton signals increasingly downfield, to 3.05 ppm in...