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Cinética de transferencia de electrones heterogénea para las fracciones redox de rutenio y ferroceno a través de
John F Smalley1, Harry O Finklea, Christopher E D Chidsey
1Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA. smalley@bnl.gov
Journal of the American Chemical Society
|February 13, 2003
Resumen
Se midieron las tasas de transferencia de electrones a través de puentes de alcanetiol. Un factor preexponencial sorprendentemente bajo sugiere que los modelos convencionales de acoplamiento electrónico y dinámica de disolventes son insuficientes para explicar el comportamiento observado.
Área de la Ciencia:
- La electroquímica es electroquímica.
- Ciencias de la superficie Ciencias de la superficie.
- La cinética química es la cinética química.
Sus antecedentes:
- La transferencia heterogénea de electrones es crucial para muchos procesos electroquímicos.
- Comprender el túnel de electrones a través de puentes moleculares es clave para diseñar dispositivos electrónicos moleculares.
- Las monocapas autoensambladas de alcanetiol (SAM) son ampliamente utilizadas para modificar las superficies de los electrodos.
Objetivo del estudio:
- Para investigar la dependencia de la temperatura de las constantes de velocidad de transferencia de electrones a través de puentes de alcanetiol de diferentes longitudes.
- Para analizar la dependencia de distancia de los factores preexponenciales en la cinética de transferencia de electrones.
- Para comparar la transferencia de electrones a través de puentes de alcanetiol con otros tipos de puentes, como el vinileno de oligofenileno.
Principales métodos:
- Medición de las constantes heterogéneas de velocidad de transferencia de electrones utilizando cronoamperometría y voltametría cíclica para puentes largos (>11 grupos de metileno).
- Utilizó la técnica indirecta de salto de temperatura inducida por láser para longitudes de puente más cortas.
- Análisis de Arrhenius de la constante de velocidad frente a los datos de temperatura para determinar los factores preexponenciales.
Principales resultados:
- Se observó un comportamiento limitante dependiente de la distancia para factores preexponenciales en longitudes cortas de puentes.
- El factor preexponencial limitante fue significativamente menor de lo predicho por los modelos de dinámica de disolventes acuosos.
- Este comportamiento limitante fue independiente de la pareja redox (ferroceno o rutenio) y el tipo de enlace (directo o éster).
Conclusiones:
- Los modelos convencionales de acoplamiento electrónico a través de puentes de alcano y la dinámica del disolvente son insuficientes para explicar los resultados experimentales.
- La flexibilidad conformacional del puente puede desempeñar un papel importante en la cinética de transferencia de electrones.
- Los hallazgos destacan la necesidad de marcos teóricos refinados para describir la transferencia interfacial de electrones a través de puentes moleculares.
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