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Girado de ángulo mágico de triple cuántica (27) Al RMN de hidróxidos de aluminio
Krishnan Damodaran1, Pattuparambil R Rajamohanan, Debojit Chakrabarty
1National Chemical Laboratory, Pune 411008, India, Unilever Research India, Mumbai 400 099, India.
Journal of the American Chemical Society
|March 28, 2002
Resumen
Los experimentos de giro mágico de ángulo cuántico triple (3Q-MAS) revelan estructuras de octaedros de aluminio en hidróxidos de aluminio. Esta técnica ayuda a asignar resonancias de aluminio, avanzando en los estudios de materiales transformados.
Área de la Ciencia:
- Espectroscopia de Resonancia Magnética Nuclear (RMN) en estado sólido Espectroscopia de Resonancia Magnética Nuclear (RMN) en estado sólido
- Ciencia de los materiales Ciencia de los materiales.
- Química Inorgánica La química inorgánica es la química inorgánica.
Sus antecedentes:
- Los hidróxidos de aluminio como la gibbsite, la bayerita y la boehmite son materiales ampliamente estudiados.
- La ampliación cuádrupolar de segundo orden en los espectros de RMN (27)Al complica el análisis de los entornos de aluminio.
Objetivo del estudio:
- Para demostrar cómo la RMN con (27) Al triple giro de ángulo mágico cuántico (3Q-MAS) puede superar la ampliación espectral.
- Para dilucidar las unidades de construcción de estructuras de octaedros de aluminio no equivalentes en hidróxidos de aluminio clave.
- Para asignar resonancias isotrópicas (27) Al a posiciones específicas de aluminio dentro de las estructuras cristalinas.
Principales métodos:
- Utilizando la espectroscopia de RMN (27) Al de giro de ángulo mágico triple cuántico (3Q-MAS).
- Realización de experimentos de RMN estándar de giro de ángulo mágico (MAS).
- Realizar cálculos ab initio para determinar los tensores del gradiente del campo eléctrico (EFG).
Principales resultados:
- Los experimentos 3Q-MAS efectivamente suprimieron la ampliación cuadrupolar de segundo orden.
- Se resolvieron distintos entornos de octaedros de aluminio en gibbsite, bayerita y boehmite.
- Los resultados combinados de 3Q-MAS/MAS y los cálculos ab initio permitieron la asignación precisa de las resonancias (27) Al a los sitios estructurales determinados por rayos X.
Conclusiones:
- La RMN 3Q-MAS es una técnica poderosa para caracterizar entornos de coordinación de aluminio en hidróxidos.
- El estudio proporciona una base para analizar materiales más complejos que contienen aluminio.
- Este trabajo facilita futuras investigaciones sobre materiales estructuralmente transformados derivados de hidróxidos básicos de aluminio.
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