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Cambio mecánico impulsado por el pH de la transferencia de electrones a la transferencia de energía entre [Ru(bpy) 3]
Claire Drolen1, Eric Conklin1, Stephen J Hetterich1
1Department of Chemistry , Amherst College , Merrill Science Building , Amherst , Massachusetts 01002 , United States.
Journal of the American Chemical Society
|August 3, 2018
Resumen
La disponibilidad de protones dicta cómo los estados excitados de rutenio tris ((bipiridina) interactúan con los derivados del ferroceno en el agua. El mecanismo de apagado cambia entre la energía y la transferencia de electrones en función del pH, revelando vías de desactivación complejas.
Área de la Ciencia:
- La fotoquímica
- Química supramolecular
- La electroquímica
Sus antecedentes:
- El rutenio tris ((bipiridina) ([Ru ((bpy) 3+) estados excitados son cruciales en la fotoquímica, sometidos a desactivación a través de la transferencia de energía o electrones.
- Los derivados del ferroceno son donantes de electrones y quenchers ampliamente utilizados en los estudios fotofísicos.
- Comprender los mecanismos de desactivación del estado excitado es clave para diseñar sistemas fotoquímicos eficientes.
Objetivo del estudio:
- Investigar la influencia de la disponibilidad de protones en las vías de desactivación en estado excitado de [Ru(bpy) 3+ por derivados de ferroceno en soluciones acuosas.
- Para aclarar el mecanismo de apagado e identificar los factores que modulan las constantes de velocidad.
- Explorar el potencial para la conmutación controlada por pH de los procesos de transferencia de energía y electrones.
Principales métodos:
- Análisis de apagado de Stern-Volmer para determinar las constantes de velocidad de apagado.
- Espectroscopia de absorción transitoria para sondear la dinámica del estado excitado.
- Síntesis y caracterización de los derivados funcionalizados del ferroceno (ferrocenil-amidinio y ferrocenil-trimetilamonio).
Principales resultados:
- Las constantes de velocidad de apagado para [Ru(bpy) 3+ por el ferrocenil-amidinio (Fc-am) fueron dependientes del pH, a diferencia de las del ferrocenil-trimetilamonio (Fc-mam).
- La espectroscopia de absorción transitoria reveló un interruptor dependiente del pH en el mecanismo de apagado para Fc-am.
- A pH bajo (Fc-am protonado), la transferencia de energía domina; a pH alto (Fc-am desprotonado), la transferencia de electrones se vuelve predominante.
- El cambio mecanicista observado no puede explicarse con argumentos simples de fuerza motriz.
Conclusiones:
- La presencia o ausencia de un protón transferible en los derivados del ferroceno modula significativamente las tasas de apagado en estado excitado de [Ru(bpy) 3+ .
- El pH de la solución puede cambiar de forma controlada el mecanismo de desactivación (transferencia de energía versus transferencia de electrones) de [Ru(bpy) 3+ por derivados específicos del ferroceno.
- Los factores más allá de la fuerza motriz termodinámica juegan un papel crítico en dictar las vías de desactivación del estado excitado en estas interacciones bimoleculares.
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