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El corannuleno como una base de Lewis: modelado computacional de la protonación y la unión de cationes de litio
M V Frash1, A C Hopkinson, D K Bohme
1Department of Chemistry, Centre for Research in Mass Spectrometry, York University, Toronto, Ontario, Canada.
Journal of the American Chemical Society
|July 6, 2001
Resumen
El modelado computacional revela el corannulene.
Área de la Ciencia:
- Química computacional es la química computacional.
- Química supramolecular de las moléculas.
- Ciencia de los materiales Ciencia de los materiales.
Sus antecedentes:
- El corannuleno, un hidrocarburo aromático policíclico curvo, sirve como un bloque de construcción fundamental para los materiales avanzados.
- Comprender su reactividad con protones y cationes es crucial para diseñar nuevas arquitecturas moleculares y materiales funcionales.
Objetivo del estudio:
- Para investigar computacionalmente los sitios de protonación y las energías en la molécula de corannuleno.
- Para determinar las ubicaciones de unión preferidas y las energías de los cationes de litio en el corannuleno.
- Para analizar los cambios de aromaticidad en el corannuleno tras la protonación utilizando desplazamientos químicos de RMN y NICS.
Principales métodos:
- Cálculos de la Teoría Funcional de Densidad (DFT) utilizando la funcional B3LYP con conjuntos de base 6-311G(d,p) y 6-31G(d,p).
- Análisis de la afinidad de los protones y las energías de unión para las interacciones de cationes de litio.
- Cálculo de los desplazamientos químicos (7) Li NMR y los desplazamientos químicos nucleares independientes (NICS) para sondear la aromaticidad.
Principales resultados:
- La protonación se produce preferentemente en el átomo de carbono más interno, formando un sigma-complejo estable con una afinidad de protones de 203 kcal mol ((-1).
- Los cationes de litio se unen preferentemente sobre el anillo de 6 en la cara convexa, con fácil movimiento a través de las caras pero una alta barrera alrededor del borde.
- La inversión de cuenco a cuenco tiene una energía de activación moderada (7-12 kcal mol(-1)), y la energía de unión Li(+) calculada es de 44 kcal mol(-1).
Conclusiones:
- El coranuleno exhibe distintas preferencias de protonación, siendo el carbono del eje el sitio más favorable.
- La unión de cationes de litio está influenciada por la curvatura y la estructura de anillo del corannuleno, con implicaciones para la química huésped-invitado.
- El análisis computacional de los cambios de RMN y NICS proporciona información sobre la estructura electrónica y la modulación de la aromaticidad en la unión del huésped.
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