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Protones en movimiento con aminas colgantes: movilidad de protones en un catalizador de níquel para la oxidación del

Molly O'Hagan¹, Wendy J Shaw, Simone Raugei

¹Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, P.O. Box 999, K2-57, Richland, Washington 99352, USA.

Journal of the American Chemical Society

|May 21, 2011

Resumen

Este estudio revela una rápida transferencia intramolecular de protones en un electrocatalizador de oxidación de hidrógeno a base de níquel. Las aminas colgantes facilitan el movimiento rápido de protones, crucial para la eficiencia catalítica y la función enzimática.

Área de la Ciencia:

Química Inorgánica La química inorgánica es la química inorgánica.
La catálisis de la catálisis.
Química biofísica y bioquímica.

Sus antecedentes:

El transporte de protones es fundamental para muchos procesos químicos y biológicos.
Los electrocatalizadores de oxidación de hidrógeno son vitales para las tecnologías de conversión de energía.
Comprender los mecanismos de transferencia de protones es clave para diseñar catalizadores y enzimas eficientes.

Objetivo del estudio:

Para investigar la transferencia intramolecular de protones en un complejo de aminas colgante de níquel.
Para determinar la cinética y la energética del intercambio de protones.
Para aclarar el papel de las aminas colgantes en la facilitación de la transferencia de protones para la catálisis de oxidación de hidrógeno.

Principales métodos:

Espectroscopia de RMN 1D de temperatura variable y temperatura variable.
Los experimentos 2D EXSY son experimentos en 2D.
Cálculos de la Teoría Funcional de la Densidad (DFT, por sus siglas en inglés)
Simulaciones de Dinámica Molecular (DM) para las simulaciones.

Principales resultados:

Intercambio de protones intramolecular observado entre el Ni y las aminas colgantes en isómeros específicos de [Ni{}P{}Cy}{}2)N{}Bn{}2H{}2}{}2+).
Las constantes de la tasa de cambio de protones oscilan entre 10^4 y 10^5 s^-1 a 25 °C para las aminas endoposicionadas.
Se identificó una barrera de intercambio de protones de ΔG‡ = 11-12 kcal/mol, con una dependencia mínima del disolvente.
Los estudios computacionales apoyaron los hallazgos experimentales, indicando la transferencia de protones mediada por metales y las isomerizaciones de silla a barco como pasos limitadores de velocidad.

Conclusiones:

El catalizador de níquel exhibe una alta movilidad intramolecular de protones, con aminas colgantes que actúan como relés de protones.
Esta movilidad es directamente relevante para acelerar las transferencias de protones en la catálisis de oxidación de hidrógeno.
Los hallazgos ofrecen información sobre el movimiento de protones en catalizadores y enzimas homogéneas, incluida la Ni-Fe hidrogenasa.

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