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Control de disolventes de los mecanismos de recombinación de carga dependientes del espín dentro de las moléculas de
Emily A Weiss1, Michael J Ahrens, Louise E Sinks
1Center for Nanofabrication and Molecular Self-Assembly, Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, USA.
Journal of the American Chemical Society
|August 5, 2004
Resumen
El comportamiento del alambre molecular de los sistemas de fenotiazina-fenil-perilendiimida (PTZ-PDI) cambia con la polaridad del disolvente. Un cambio de tolueno a MTHF invirtió el efecto del campo magnético en la recombinación de pares de iones radicales, alterando las vías de recombinación de carga.
Área de la Ciencia:
- La fotoquímica es la fotoquímica.
- La electrónica molecular es la electrónica molecular.
- Química supramolecular de las moléculas.
Sus antecedentes:
- Los sistemas de donante-puente-aceptor (DBA) con puentes de p-fenileno exhiben propiedades de alambre molecular.
- Las dinámicas de recombinación de pares de iones radicales (RP) son sensibles a los campos magnéticos externos, lo que permite la medición de la división singleta-tripla (2J).
- El acoplamiento electrónico (VDA^2) entre los sitios donante y aceptante influye en la recombinación de RP y los efectos del campo magnético (MFE).
Objetivo del estudio:
- Para investigar la influencia de la polaridad del disolvente en los mecanismos de recombinación de carga en los alambres moleculares PTZ-(Ph) n-PDI.
- Para determinar si el efecto del campo magnético (MFE) en la población de RP puede ser modulado por el entorno del disolvente.
- Comprender la interacción entre la estructura molecular, los efectos del disolvente y las vías de recombinación de carga.
Principales métodos:
- Síntesis y caracterización de los sistemas de donante-puente-aceptor PTZ-(Ph) n-PDI.
- Estudios espectroscópicos en tolueno y 2-metiltetrahidrofurano (MTHF) para monitorear las poblaciones de RP.
- Mediciones del efecto de campo magnético (MFE) para sondear las vías de división y recombinación singlet-triplet.
Principales resultados:
- El puente oligomérico de p-fenileno funciona como un cable molecular, pasando de la dependencia exponencial a la distancia lineal de la recombinación de RP.
- Se observó una "inversión" del MFE en la población de RP cuando se cambió el disolvente del tolueno al MTHF más polar para PTZ+*-(Ph) 4-PDI-* y PTZ+*-(Ph) 5-PDI-*.
- La inversión MFE sugiere un cambio en las contribuciones relativas de las vías de recombinación de carga singlet (CRS) y triplet (CRT).
Conclusiones:
- El mecanismo de recombinación de carga en los cables moleculares PTZ-PDI es sensible al entorno del disolvente circundante.
- Los disolventes polares como el MTHF pueden estabilizar el estado de RP, favoreciendo la recombinación de carga simple (CRS) y alterando el MFE.
- Este estudio pone de relieve la importancia de los factores ambientales en la sintonización de la funcionalidad de los cables moleculares y los procesos de transferencia de carga.
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