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Distorsión del estado excitado en complejos fotocrómicos de sulfóxido de rutenio
Beth Anne McClure1, Eric R Abrams, Jeffrey J Rack
1Department of Chemistry and Biochemistry, Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701, USA.
Journal of the American Chemical Society
|March 31, 2010
Resumen
Los complejos fotocrómicos de sulfóxido de rutenio se someten a una isomerización desencadenada por la luz entre los estados de enlace S y enlace O. Este proceso reversible, influenciado por los sustituyentes de azufre, se produce a través de un mecanismo no adiabático con rendimientos cuánticos y escalas de tiempo variables.
Área de la Ciencia:
- Coordinación Química de la Coordinación
- La fotoquímica es la fotoquímica.
- Ciencia de los materiales Ciencia de los materiales.
Sus antecedentes:
- Los materiales fotocrómicos exhiben cambios de color reversibles tras la exposición a la luz.
- Los complejos de rutenio son conocidos por sus diversas propiedades fotofísicas.
- Los ligandos de sulfóxido ofrecen modos de coordinación y reactividad únicos.
Objetivo del estudio:
- Para sintetizar y caracterizar nuevos complejos fotocrómicos de sulfóxido de rutenio.
- Para investigar el mecanismo de la isomerización inducida por la luz en estos complejos.
- Explorar la influencia de los efectos electrónicos sustituyentes en el comportamiento fotocrómico.
Principales métodos:
- Síntesis y caracterización de complejos de rutenio (II) con bipiridina y sus ligandos sulfóxido.
- Espectroscopia de absorción y emisión UV-Vis para estudiar las transiciones electrónicas.
- Espectroscopia de absorción transitoria de femtosegundos para sondear la dinámica del estado excitado.
- Mediciones electroquímicas para evaluar las propiedades redox.
Principales resultados:
- Síntesis exitosa de complejos [Ru(bpy) ((2) ((OSOR))) ((+) con varios ligandos de sulfóxido (OSOBn, OSONap, OSOBnF ((5)).).
- Se ha demostrado la isomerización fototriggerada de la coordinación de sulfóxido de enlace S a enlace O tras la excitación de transferencia de carga.
- Se observó una isomerización reversible en el metanol con reversión térmica al isómero con enlace S.
- Rendimientos cuánticos determinados (Phi(s-->o)) y constantes de tiempo de isomerización (tau(s-->o)) influenciados por los sustitutos de azufre.
- Los datos espectroscópicos indicaron distorsiones significativas entre los estados básico y excitado, que implican modos de vibración específicos.
Conclusiones:
- Los complejos de sulfóxido de rutenio sintetizados exhiben fotocromatismo eficiente.
- La isomerización procede a través de un mecanismo no adiabático desde un estado relajado (3) MLCT.
- Los efectos de sustitución sobre el azufre modulan las propiedades del isómero con enlace S.
- Los modos de vibración de baja frecuencia juegan un papel crucial en la vía de isomerización.
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