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Implicaciones mecánicas de la transferencia de protones acoplada a la transferencia de electrones
E L Lebeau1, R A Binstead, T J Meyer
1Los Alamos National Laboratory, MS A127, Los Alamos, New Mexico 87545, USA.
Journal of the American Chemical Society
|October 25, 2001
Resumen
Este estudio investiga la cinética de transferencia de electrones entre los complejos de rutenio y osmio, revelando vías dependientes del pH influenciadas por la transferencia de protones. Se aclararon mecanismos complejos de reacción, destacando los factores que afectan la eficiencia de la transferencia de electrones.
Área de la Ciencia:
- Química Inorgánica La Química Inorgánica es la química inorgánica.
- La electroquímica es electroquímica.
- La cinética química es la cinética química.
Sus antecedentes:
- Los complejos polipiridil de rutenio (Ru) y osmio (Os) son cruciales en los estudios de transferencia de electrones.
- Comprender la transferencia electrón-protón es vital para los procesos catalíticos y redox.
Objetivo del estudio:
- Investigar la cinética de las reacciones de transferencia de electrones que involucran complejos cis-Ru (IV/III/II) y Os (II/III).
- Para dilucidar el papel del pH y la transferencia de protones en estas reacciones redox.
- Para analizar los complejos mecanismos de reacción, incluidas las vías de competencia y las etapas que limitan la velocidad.
Principales métodos:
- Estudió la cinética de transferencia de electrones en ambas direcciones hacia adelante y hacia atrás a través de un rango de pH de 1 a 8.
- Utilizó un modelo de doble "esquema cuadrado" que incorpora la transferencia gradual de electrones y protones.
- Incluido el equilibrio de desproporción de cis-[Ru(III)(bpy)2(py)(OH)]2+ en el análisis cinético.
Principales resultados:
- Identificó cinética de reacción dependiente del pH atribuida a los equilibrios ácido-base, no a las variaciones de la fuerza motriz.
- Caminos concurrentes observados iniciados por la transferencia de electrones o protones, con importancia relativa dependiente del pH.
- Se encontró una inhibición significativa de la transferencia de electrones a la esfera externa debido a las grandes diferencias de pK entre las especies Ru.
- Determinados pasos limitadores de velocidad que implican la pérdida de protones de complejos Ru específicos.
Conclusiones:
- La transferencia de electrones es de esfera externa y no está acoplada a la transferencia de protones en estos sistemas.
- La interacción entre la transferencia de electrones, la transferencia de protones y el pH crea una cinética de reacción compleja.
- El equilibrio de desproporcionamiento y las diferencias de pK (a) influyen significativamente en las vías y velocidades de reacción.
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