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Sobre el origen de la actividad óptica mostrada por los nanocúmulos metálicos protegidos con ligando quiral
Ariadna Sánchez-Castillo1, Cecilia Noguez, Ignacio L Garzón
1Instituto de Física, Universidad Nacional Autónoma de México, Apartado Postal 20-364, 01000 México, DF, México.
Journal of the American Chemical Society
|January 22, 2010
Resumen
Los ligandos quirales en los racimos de oro crean actividad óptica. Este estudio revela que tanto el cúmulo como el cúmulo
Área de la Ciencia:
- Química computacional y nanociencia.
- Espectroscopia y propiedades ópticas de los materiales.
Sus antecedentes:
- Los grupos metálicos protegidos por ligandos pueden mostrar actividad óptica cuando las moléculas quirales se utilizan como ligandos protectores.
- Las teorías existentes para la actividad óptica en estos materiales a nanoescala incluyen el núcleo de clúster quiral, el efecto de campo disimétrico y el modelo de huella quiral.
- Comprender el origen de la actividad óptica es crucial para el diseño de nanomateriales funcionales.
Objetivo del estudio:
- Investigar el origen fisicoquímico de la actividad óptica en el grupo [Au(25)(SG)(18)](-) protegido por glutatión utilizando cálculos teóricos.
- Para aclarar la contribución del núcleo metálico y los modos de unión ligando-metal al espectro del dicroísmo circular (CD).
Principales métodos:
- Primeros principios estudio teórico del espectro del dicroísmo circular (CD).
- Cálculo del espectro de CD para un grupo protegido por cisteína [Au(25)(SR(cys))(18)](-).
- Análisis de la estructura electrónica y las interacciones ligando-metal.
Principales resultados:
- El espectro de CD calculado para el grupo protegido por cisteína coincide estrechamente con los datos experimentales para el grupo protegido por glutatión.
- Tanto el núcleo metálico distorsionado como los modos específicos de unión tiolato-oro contribuyen a la actividad óptica observada.
- La disposición asimétrica de los ligandos mejora la débil señal de CD que surge de las distorsiones del núcleo.
Conclusiones:
- La actividad óptica de los grupos metálicos protegidos por ligando quiral surge de una interacción simultánea de múltiples mecanismos, no de uno solo dominante.
- La orientación y la estabilidad de los ligandos tiolatos influyen significativamente en la forma de la línea CD y en la respuesta óptica general.
- Este trabajo proporciona una visión más profunda de las relaciones estructura-propiedad que rigen la actividad óptica de los nanocúmulos de oro.
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