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Caminos de transferencia de electrones competitivos en estructuras de hidrocarburos: acoplamiento de enlace a través
Subhasis Chakrabarti1, Min Liu, David H Waldeck
1Chemistry Department, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
Journal of the American Chemical Society
|February 24, 2007
Resumen
La transferencia de electrones en moléculas en forma de U (1DBA y 2DBA) ocurre a través de grupos aromáticos colgantes, no el puente molecular. Este mecanismo de grupo colgante mejora significativamente las tasas de recombinación de carga, lo que demuestra su importancia en los sistemas moleculares.
Área de la Ciencia:
- Química Física es la química física.
- La electrónica molecular es la electrónica molecular.
- Química orgánica es la química orgánica.
Sus antecedentes:
- Investigar los mecanismos de transferencia de electrones es crucial para el diseño de dispositivos electrónicos moleculares.
- Las moléculas en forma de U con grupos donante-aceptante ofrecen vías sintonizables para el transporte de cargas.
- El papel de los grupos colgantes en la modulación de las tasas de transferencia de electrones requiere una mayor aclaración.
Objetivo del estudio:
- Explorar las vías de transferencia de electrones a través de contactos no unidos en dos moléculas DBA en forma de U (1DBA y 2DBA).
- Para cuantificar el acoplamiento electrónico y los parámetros de energía que rigen la transferencia de electrones.
- Para comparar hallazgos experimentales con predicciones computacionales para la separación y recombinación de cargas.
Principales métodos:
- Síntesis y caracterización de moléculas DBA en forma de U (1DBA y 2DBA) con distintos grupos colgantes.
- Medición de las tasas de transferencia de electrones en disolventes orgánicos de diferentes polaridades.
- Cálculo de elementos de la matriz de acoplamiento electrónico, energía libre de Gibbs y energía de reorganización a partir de datos fotofísicos.
Principales resultados:
- El acoplamiento electrónico para la separación de cargas (V(CS)) fue de 147 cm-1 para 1DBA y 274 cm-1 para 2DBA, atribuido al carácter electrónico del grupo colgante.
- Se observó fluorescencia de transferencia de carga (CT) en 2DBA, lo que permitió la determinación del acoplamiento de recombinación de carga (V(CR)) a ~ 500 cm-1.1.
- V ((CR) en 2DBA fue significativamente mayor que V ((CS) y dos órdenes de magnitud mayor que en una molécula similar que carece de un grupo colgante.
Conclusiones:
- La transferencia de electrones en estos sistemas en forma de U se produce predominantemente a través del grupo aromático colgante, no el puente molecular.
- El mecanismo del grupo colgante mejora significativamente las tasas de recombinación de carga debido a los cambios geométricos en el estado de carga separada.
- Estos hallazgos demuestran inequívocamente la eficacia del mecanismo de transferencia de electrones de grupo a través-dependiente en arquitecturas moleculares en forma de U.
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