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A Technical Guide for Performing Spectroscopic Measurements on Metal-Organic Frameworks
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Aprovechando la dinámica conformacional para facilitar la formación y el atrapamiento de fotoproductos de
Heather A Meylemans1, Joshua T Hewitt, Mirvat Abdelhaq
1Department of Chemistry and Biochemistry, University of Colorado at Boulder, Boulder, Colorado 80309, USA.
Journal of the American Chemical Society
|August 6, 2010
Resumen
Los nuevos sistemas de donante-aceptor de electrones fotoinducidos utilizan la masa estérica para controlar los estados de carga separada. Esta estrategia mejora la formación y el almacenamiento de estos estados ajustando la geometría del ligando y la dinámica conformacional.
Área de la Ciencia:
- La fotoquímica es la fotoquímica.
- Química supramolecular de las moléculas.
- Ciencia de los materiales Ciencia de los materiales.
Sus antecedentes:
- Los sistemas de donante-aceptor de electrones (D-A) fotoinducidos son cruciales para la conversión y el almacenamiento de energía.
- El ajuste de las propiedades electrónicas y estructurales de los sistemas D-A es clave para optimizar su rendimiento.
- El diseño de los ligandos juega un papel importante en el control del comportamiento de los complejos D-A.
Objetivo del estudio:
- Para sintetizar y caracterizar nuevos sistemas de donante-aceptor de electrones (DA) fotoinducidos.
- Para investigar el efecto del bulto estérico en la dinámica conformacional del ligando puente.
- Establecer una estrategia para controlar la formación y el almacenamiento de estados de carga separada.
Principales métodos:
- Síntesis de tres nuevos complejos de Ru(II) -bipiridinium D-A con diferentes volúmenes estéricos.
- Mediciones electroquímicas para determinar las fuerzas motrices para la transferencia de electrones (DeltaG(ET)) y la transferencia de electrones hacia atrás (DeltaG(BET)).
- Espectroscopia con resolución de tiempo (aprox. 100 fs pulsos láser) para estudiar la dinámica de transferencia de electrones fotoinducida.
- Análisis de Franck-Condon de los espectros de emisión de los complejos de modelos.
Principales resultados:
- Las fuerzas impulsoras de la transferencia de electrones (ET) y la transferencia de electrones hacia atrás (BET) fueron invariantes en toda la serie.
- La transferencia de electrones fotoinducida (ET) se produjo rápidamente (29-57 ps) a pesar del aumento del volumen estérico.
- La vida útil de los estados separados por carga (tau ((BET)) aumentó significativamente (hasta 8 veces) con el volumen estérico (98-789 ps).
Conclusiones:
- Las dinámicas de torsión basadas en ligandos, impulsadas por la deslocalización de electrones intraligandos, facilitan la ET rápida.
- Las repulsiones estéricas en el estado de carga separada impulsan la dinámica conformacional inversa, aumentando las vidas.
- El control estérico de la geometría del ligando ofrece una nueva estrategia para mejorar la formación y el almacenamiento de estados de carga separada.
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