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Los estados excitados de transferencia de carga de ligando a metal no localizados se encuentran en (Cp) 2Ti (IV)
Elizabeth L Patrick1, Chad J Ray, Grant D Meyer
1Department of Chemistry, The University of New Mexico, Albuquerque, New Mexico 87131, USA.
Journal of the American Chemical Society
|May 2, 2003
Resumen
Este estudio revela una intensa fosforescencia en el metalloceno de titanio, (Cp) 2 Ti ((NCS) 2), a partir de un tripleto de transferencia de carga de ligando a metal en estado excitado. La espectroscopia infrarroja con resolución de tiempo confirma la naturaleza deslocalizada de este estado excitado sin romper la simetría.
Área de la Ciencia:
- Coordinación Química de la Coordinación
- La fotofísica es la fotofísica.
- La espectroscopia es una técnica de espectroscopia.
Sus antecedentes:
- Los metallocenos de titanio son compuestos versátiles con aplicaciones en catálisis y ciencias de los materiales.
- Los estados excitados de transferencia de carga de ligando a metal (LMCT) son cruciales para la comprensión de los procesos fotofísicos en complejos de coordinación.
- La fosforescencia de los estados LMCT en d(0) metallocenos es relativamente inexplorada.
Objetivo del estudio:
- Para investigar las propiedades fotofísicas del metalloceno de titanio doblado d(0) (Cp) 2Ti ((NCS) 2.
- Para caracterizar el estado excitado del triplete de transferencia de carga de ligando a metal utilizando métodos espectroscópicos y computacionales.
- Para explorar la dinámica del estado excitado utilizando espectroscopia infrarroja con resolución temporal a temperaturas criogénicas.
Principales métodos:
- Espectroscopia de fosforescencia a baja temperatura (77 K) en vidrio orgánico y sustratos de PMMA.
- Cálculos químicos cuánticos (DFT) para determinar el parentesco orbital y la estructura electrónica.
- Espectroscopia infrarroja (TRIR) de baja temperatura (77 K) con resolución de tiempo en la escala de tiempo de nanosegundos.
- Análisis de descomposición del valor singular (SVD) de los datos TRIR.
Principales resultados:
- Se observó una intensa fosforescencia en el estado excitado del trío del LMCT de (Cp) 2 Ti (NCS) 2 a 77 K.
- La espectroscopia TRIR reveló bandas IR transitorias en la región de estiramiento de la CN correspondiente al estado excitado triple.
- El análisis indicó un estado excitado del LMCT deslocalizado sin ruptura de simetría significativa, respaldado por cálculos y datos experimentales.
Conclusiones:
- El estudio proporciona la primera investigación infrarroja con resolución temporal de un estado excitado LMCT en un metalloceno de titanio d(0).
- Los hallazgos demuestran que el estado excitado del triplete LMCT está deslocalizado a través de ambos ligandos NCS.
- La espectroscopia criogénica TRIR en sustratos de película delgada es una herramienta poderosa para caracterizar estados excitados transitorios.
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