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Mecanismo de la transferencia de electrones de autointercambio de cobalto

Andrew M Ullman¹, Daniel G Nocera

¹Department of Chemistry and Chemical Biology, Harvard University , 12 Oxford Street, Cambridge, Massachusetts 02138, United States.

Journal of the American Chemical Society

|August 31, 2013

Resumen

Los investigadores sintetizaron un modelo de racimo de cobalto para los catalizadores de división del agua. La disociación aniónica acelera la transferencia de electrones, explicando los mecanismos de autorreparación del catalizador y resolviendo las controversias de la reacción redox del cobalto.

Área de la Ciencia:

Química Inorgánica La Química Inorgánica es la química inorgánica.
La catálisis es la catálisis.
La electroquímica es electroquímica.

Sus antecedentes:

Los complejos que evolucionan cobalto-oxígeno (Co-OEC) son cruciales para la catálisis de la división del agua.
Comprender el autointercambio redox de cobalto es vital para la eficiencia y estabilidad del catalizador.
Estudios anteriores se enfrentaron a desafíos para explicar los efectos aniónicos y los mecanismos de autointercambio de cobalto.

Objetivo del estudio:

Para sintetizar y caracterizar un grupo de cobalto heptanuclear como un modelo para Co-OECs.
Para investigar la cinética de transferencia de electrones y el mecanismo del cúmulo de cobalto.
Aclarar el papel de los aniones en el ciclo catalítico y el autointercambio de cobalto.

Principales métodos:

Síntesis de grupos de cobalto heptanucleares en los estados Co(II) 7 y de valencia mixta Co(III) Co(II) 6.
Caracterización cristalográfica para determinar la estructura del racimo y la asociación de aniones.
Método de intercambio de isótopos para medir las constantes de tasa de transferencia de electrones de autocambio.

Principales resultados:

Se observaron núcleos de racimo similares para ambos estados de oxidación, con diferencias clave en el átomo central de cobalto.
Un anión se asocia con el núcleo del racimo a través de enlaces de hidrógeno.
Se midió una tasa de transferencia de electrones de autointercambio anormalmente lenta, lo que sugiere que la disociación aniónica acelera la transferencia de carga.

Conclusiones:

Los hallazgos apoyan un mecanismo de transferencia de carga acelerado por la disociación aniónica, lo que explica la dependencia aniónica inversa en la auto-reparación Co-OEC.
El estudio aborda la controversia que rodea la reacción de autointercambio Co2+/3+) de los complejos hexaaquáticos.
El átomo de cobalto central encapsulado evita el puenteamiento directo del agua, ofreciendo información sobre las vías catalíticas.

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