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Las propiedades ópticas no lineales y la dinámica del estado excitado de las porfirinas expandidas altamente
Zin Seok Yoon1, Jung Ho Kwon, Min-Chul Yoon
1Department of Chemistry and Center for Ultrafast Optical Characteristics Control, Yonsei University, Seoul 120-749, Korea.
Journal of the American Chemical Society
|October 26, 2006
Resumen
Las porfirinas expandidas muestran un fuerte vínculo entre los marcadores de aromaticidad, la planaridad molecular y los valores de absorción de dos fotones (TPA). Esto sugiere que el TPA puede medir cuantitativamente la aromaticidad en sistemas macrocíclicos.
Área de la Ciencia:
- * Química computacional y espectroscopia.
- * Ciencias orgánicas y de los materiales.
Sus antecedentes:
- * Las porfirinas expandidas son sistemas macrocíclicos con propiedades electrónicas sintonizables.
- * La aromaticidad es una propiedad clave que influye en el comportamiento molecular y la estabilidad.
- * El Cambio Químico Independiente del Núcleo (NICS) y la absorción de dos fotones (TPA) son indicadores importantes de la estructura electrónica.
Objetivo del estudio:
- * Investigar la correlación entre el NICS, la planaridad molecular y el TPA en las porfirinas expandidas.
- * Explorar la relación entre la estructura electrónica y las propiedades ópticas.
- * Establecer el TPA como una medida cuantitativa de la aromaticidad en sistemas macrocíclicos pi-conjugados.
Principales métodos:
- * Cálculo de los valores NICS para varias porfirinas expandidas.
- * Medición de los valores de TPA para los compuestos sintetizados.
- * Análisis de la planaridad molecular y la estructura electrónica (pi-electrones).
Principales resultados:
- * Se encontró una fuerte correlación entre los valores de NICS, planaridad y TPA.
- * Los sistemas antiaromáticos ([28]hexafirina, ametirina) mostraron un NICS positivo y un alto TPA.
- * Se observó una correlación lineal entre NICS y TPA para los congéneres aromáticos.
- * El aumento de la flexibilidad en los sistemas de 26 pi-electrones se correlacionó con la disminución de la vida útil del estado excitado y el aumento de TPA.
Conclusiones:
- * Los valores de TPA sirven como una medida experimental cuantitativa de la aromaticidad en sistemas macrocíclicos pi-conjugados.
- * La flexibilidad molecular influye en las propiedades del estado excitado y el TPA.
- * NICS, planaridad y TPA son indicadores interconectados de las propiedades electrónicas en las porfirinas expandidas.
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