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Tensor de dicroísmo circular de una hélice de triarilmetilo en cristales de clorato de sodio
Yonghong Bing1, David Selassie, Ruthanne H Paradise
1Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195, USA.
Journal of the American Chemical Society
|May 8, 2010
Resumen
El Perucca es una peruca.
Área de la Ciencia:
- Química del estado sólido.
- La espectroscopia quiróptica es una técnica de espectroscopia.
- La cristalografía es una técnica de cristalografía.
Sus antecedentes:
- 1919 informe de dispersión rotatoria óptica anómala por Perucca de clorato de sodio quiral (NaClO(3)) cristales.
- Las observaciones de Perucca sugirieron la adsorción enantioselectiva de moléculas de colorante en forma de hélice en cristales inorgánicos.
- Este estudio reexamina los hallazgos de Perucca utilizando técnicas modernas en cristales de NaClO ((3) teñidos con azul de anilina.
Objetivo del estudio:
- Para investigar las propiedades quirópticas de cristales azules mezclados NaClO(3)-anilina.
- Para analizar el dicroísmo lineal y circular, y los fenómenos de extinción circular.
- Establecer un modelo de cristal mixto y comprender la relación entre las propiedades ópticas y la configuración molecular.
Principales métodos:
- Espectroscopia de absorción de luz polarizada por absorción de luz.
- Medición del dicroísmo lineal y la birefringencia lineal.
- Dicroísmo circular y mediciones de extinción circular en múltiples orientaciones de cristal.
- Cálculo ab initio de los momentos de transición electrónica y tensores de dicroísmo circular para el azul de anilina.
Principales resultados:
- Se caracterizaron las propiedades ópticas detalladas (lineales y circulares) de las secciones (001), (110) y (111) de cristales teñidos de NaClO ((3)).
- El dicroísmo lineal mapeó los momentos de dipolo de transición en relación con las caras de crecimiento del cristal.
- Las mediciones de dicroísmo circular definen un tensor bisignado relativo a las caras de cristal.
- Los cálculos ab initio apoyaron un modelo consistente de cristal mixto.
- Se aclaró la distinción entre dicroísmo circular y extinción circular anómala basada en la dirección cristalográfica y las propiedades de simetría.
- El análisis reveló que Perucca observó una convolución de propiedades ópticas lineales y circulares.
Conclusiones:
- Un cristal inorgánico quiral (NaClO(3) puede exhibir propiedades quirópticas significativas incluso con una baja resolución enantiomérica de las moléculas adsorbidas.
- Los fenómenos ópticos observados (dicroísmo circular y extinción circular anómala) dependen de la orientación cristalográfica.
- Una fuerte respuesta quiróptica en estado sólido no confirma automáticamente la resolución enantiomérica.
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