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Hacer que las aminas sean bases fuertes: estabilización termodinámica de huéspedes protonados en un huésped
Michael D Pluth1, Robert G Bergman, Kenneth N Raymond
1Department of Chemistry, University of California, Berkeley, California 94720-1460, USA.
Journal of the American Chemical Society
|August 24, 2007
Resumen
Un huésped supramolecular altera dramáticamente la basicidad de las aminas y fosfinas encapsuladas. Este huésped selectivamente une a los huéspedes, estabilizando sus formas protonadas y creando bases sólidas.
Área de la Ciencia:
- Química supramolecular de las moléculas.
- Química entre anfitrión y huésped.
- Física Química orgánica Física Química orgánica
Sus antecedentes:
- Los ensamblajes supramoleculares pueden influir en las propiedades de las moléculas encapsuladas.
- La modulación de la basicidad de los huéspedes es crucial para diversas aplicaciones químicas.
Objetivo del estudio:
- Investigar el efecto de un ensamblaje supramolecular cargado y con cavidad sobre la basicidad de los huéspedes protonados de aminas y fosfinas.
- Para determinar los factores que influyen en la encapsulación de invitados y el intercambio dentro del anfitrión.
Principales métodos:
- Interacciones metal-ligando para formar el huésped supramolecular.
- Espectroscopia de Resonancia Magnética Nuclear (RMN) (específicamente RMN 31P) para estudios de protonación.
- Espectrometría de masas y estudios dependientes del pH para la confirmación de la encapsulación del huésped.
- Método de recuperación de inversión selectiva para medir las tasas de autocambio de huéspedes.
Principales resultados:
- El huésped supramolecular encapsula selectivamente a los huéspedes protonados de aminas y fosfinas en función de su tamaño.
- La protonación de los huéspedes encapsulados se confirmó a través de estudios espectroscópicos y de pH.
- Las tasas de autointercambio de huéspedes se correlacionan con el tamaño del huésped, no con la basicidad.
- Las basicidades efectivas de las aminas encapsuladas se desplazaron hasta en 4,5 unidades pKa, estabilizando la forma protonada.
Conclusiones:
- El huésped supramolecular mejora significativamente la basicidad de los huéspedes encapsulados.
- Este efecto estabilizador transforma las aminas y las fosfinas en bases fuertes.
- El estudio demuestra un control preciso sobre las propiedades de los huéspedes a través de las interacciones huésped-anfitrión.
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