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El control del disolvente de la localización de la carga en los aniones de radicales dinitroaromáticos con 11 enlaces
Stephen F Nelsen1, Michael N Weaver, João P Telo
1Department of Chemistry, University of Wisconsin, 1101 University Avenue, Madison, Wisconsin 53706-1396, USA. nelsen@chem.wisc.edu
Journal of the American Chemical Society
|May 15, 2007
Resumen
Se estudiaron los espectros de carga localizada y carga deslocalizada de los aniones radicales dinitroaromáticos en varios disolventes. La polaridad del disolvente influye en el acoplamiento electrónico, afectando las características espectrales y validando las predicciones teóricas.
Área de la Ciencia:
- La electroquímica es electroquímica.
- La espectroscopia es una técnica de espectroscopia.
- Química orgánica es la química orgánica.
Sus antecedentes:
- Los aniones radicales dinitroaromáticos exhiben características espectrales distintas dependiendo de la distribución de la carga.
- La polaridad del disolvente es un factor crítico que influye en el acoplamiento electrónico en sistemas moleculares.
Objetivo del estudio:
- Para investigar el comportamiento espectral dependiente del disolvente de los aniones radicales 4,4'-dinitrostilbeno, 4,4'-dinitrotolano y 4,4'-dinitroazobenzeno.
- Determinar la energía de transición para la deslocalización de carga y evaluar modelos teóricos para el acoplamiento electrónico.
Principales métodos:
- Se empleó espectroscopia óptica para analizar los aniones radicales en varios disolventes (THF, HMPA, DMPU, DMF, DMSO, MeCN).
- Se analizaron las formas de las bandas espectrales y las estructuras vibratorias para diferenciar entre los estados electrónicos localizados y deslocalizados.
Principales resultados:
- Los aniones radicales 4,4'-dinitrostilbeno y 4,4'-dinitrotolano mostraron una transición de espectros deslocalizados a espectros localizados con un aumento de la polaridad del disolvente.
- El anión radical 4,4'-dinitroazobenzeno se mantuvo deslocalizado en los disolventes estudiados, con cambios sutiles en el ancho de la línea espectral.
- Los cambios espectrales observados se correlacionan con las propiedades del disolvente y proporcionan información sobre la localización / deslocalización de la carga.
Conclusiones:
- La polaridad del disolvente dicta el acoplamiento electrónico y la distribución de la carga en estos aniones radicales dinitroaromáticos.
- Se ha demostrado que el método Hush para calcular el acoplamiento electrónico subestima los valores de los compuestos límite.
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