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La isomerización en picosegundos en complejos fotocromáticos de rutenio-dimetil sulfóxido
Aaron A Rachford1, Jeffrey J Rack
1Department of Chemistry and Biochemistry, Ohio University, Athens, Ohio 45701, USA.
Journal of the American Chemical Society
|November 2, 2006
Resumen
Los complejos de rutenio con ligandos de dimetilsulfóxido (dmso) se someten a isomerización intramolecular en estado excitado. Este estudio cuantifica las tasas y los mecanismos de isomerización S-to-O en estos compuestos fotoactivos.
Área de la Ciencia:
- La fotoquímica es la fotoquímica.
- Coordinación Química de la Coordinación
- La espectroscopia es una técnica de espectroscopia.
Sus antecedentes:
- Los complejos de rutenio con terpiridina (tpy) y bipiridina (bpy) o ligandos de piridinacarboxilato (pic) son fotoactivos.
- Los ligandos del dimetilsulfóxido (dmso) pueden sufrir isomerización intramolecular en estado excitado.
Objetivo del estudio:
- Para investigar la isomerización S-->O intramolecular en estado excitado de los ligandos dmso en complejos de rutenio.
- Para determinar la cinética y los mecanismos de este proceso de isomerización.
Principales métodos:
- Se utilizó la espectroscopia de absorción transitoria de picosegundos para monitorear la isomerización.
- Se empleó el análisis global de datos espectrales para extraer constantes de tiempo.
- Se recopilaron datos electroquímicos, de absorción y de emisión.
Principales resultados:
- Dos complejos de rutenio, [Ru ((tpy) ((bpy) ((dmso) ] ((2+) y trans-[Ru ((tpy) ((pic) ((dmso) ] ((+), exhibieron una cinética de desintegración biexponencial.
- Se determinó que las constantes de tiempo de isomerización eran de 1,5 ns para el primer complejo y 480 ps para el segundo.
- Los estados excitados térmicamente relajados fueron identificados como estados terpiridina-localizados (3) MLCT.
Conclusiones:
- Las reacciones rápidas de ruptura de enlaces y de creación de enlaces pueden ocurrir desde (3) estados excitados de MLCT.
- El estudio proporciona información sobre la reactividad de los complejos de rutenio fotoexcitados.
- Se construyeron diagramas de estado electrónico para dilucidar la reactividad observada.
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