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Controlar la transferencia de electrones en las moléculas donante-puente-aceptante utilizando puentes de conjugado

Annie Butler Ricks¹, Gemma C Solomon, Michael T Colvin

¹Department of Chemistry and Argonne-Northwestern Solar Energy Research Center, Northwestern University, Evanston, Illinois 60208-3113, United States.

Journal of the American Chemical Society

|October 15, 2010

Resumen

La separación de carga fotoiniciada (CS) es significativamente más lenta a través de puentes conjugados cruzados en comparación con los lineales, lo que sugiere un cambio a las vías sigma. Esto impacta la dinámica de transferencia de electrones en las moléculas donante-puente-aceptante.

Área de la Ciencia:

La fotoquímica es la fotoquímica.
La electrónica molecular es la electrónica molecular.
Química orgánica es la química orgánica.

Sus antecedentes:

Las moléculas de donante-puente-aceptor (D-B-A) son cruciales para comprender la separación de carga (CS) y la recombinación (CR).
Las propiedades electrónicas del puente influyen significativamente en la eficiencia de los procesos CS y CR.

Objetivo del estudio:

Para comparar y contrastar CS y CR fotoiniciados en moléculas D-B-A con conjugación puente variable (conjugado cruzado, conjugado lineal, saturado).
Para investigar el papel de la estructura de puente en las tasas de transferencia de electrones y acoplamiento electrónico.

Principales métodos:

Se empleó espectroscopia de resolución temporal para estudiar la dinámica de CS y CR.
Se realizaron cálculos de conductividad molecular para analizar el acoplamiento electrónico a través del puente.

Principales resultados:

CS a través de un puente de 1,1-difenil eteno conjugado cruzado fue 30 veces más lento que a través de su contraparte lineal trans-estilbeno, comparable a un puente de difenil metano saturado.
CS a través de un puente de xantona cruzado conjugado mostró tasas similares a su contraparte lineal trans-estilbeno.
Los cálculos de conductividad molecular revelaron efectos de interferencia cuántica en sistemas conjugados cruzados, alterando el acoplamiento electrónico.

Conclusiones:

La conjugación cruzada reduce significativamente la contribución orbital pi al acoplamiento electrónico donante-aceptor, favoreciendo las vías sigma para CS.
Los efectos de interferencia cuántica en puentes conjugados cruzados modulan el acoplamiento electrónico, alineándose con las tendencias experimentales de velocidad de transferencia de electrones.

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