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Los sitios activos complementarios causan una reactividad selectiva por tamaño de los aniones del racimo de aluminio

Patrick J Roach¹, W Hunter Woodward, A W Castleman

¹Departments of Chemistry and Physics, Pennsylvania State University, University Park, PA 16802, USA.

Science (New York, N.Y.)

|January 24, 2009

Resumen

Los aniones de racimo de aluminio reaccionan con el agua de manera diferente en función del tamaño, impulsados por la estructura geométrica, no por las conchas electrónicas. Los arreglos específicos del sitio en los grupos Al16-, Al17- y Al18- producen gas hidrógeno.

Área de la Ciencia:

Química Física es la química física.
Ciencia de los materiales Ciencia de los materiales.
Ciencias de la superficie Ciencias de la superficie.

Sus antecedentes:

Las reacciones de grupos metálicos con moléculas pequeñas a menudo dependen del tamaño.
Si bien los modelos de capas electrónicas explican las reacciones de oxígeno con aniones de clúster de aluminio, otras reacciones pueden seguir principios diferentes.

Objetivo del estudio:

Para investigar la selectividad de tamaño en las reacciones de aniones de racimo de aluminio con agua.
Para determinar los factores subyacentes (geométricos frente a electrónicos) que rigen esta reactividad.

Principales métodos:

Reacción de aniones de racimo de aluminio con moléculas de agua.
Análisis de productos de reacción y tamaños de racimo.
Correlación de la reactividad con la estructura del clúster.

Principales resultados:

Selectividad de tamaño observada en las reacciones de aniones de racimo de aluminio con agua.
La reactividad está dictada por la estructura geométrica y las disposiciones específicas del sitio de la superficie, no por los cierres electrónicos de la carcasa.
Disposiciones idénticas de sitios activos en grupos de Al16-, Al17- y Al18- conducen a la producción de H2 a partir del agua.

Conclusiones:

La selectividad de tamaño de las reacciones de aniones de racimo de aluminio con agua se rige por factores geométricos, específicamente la disposición de los sitios de superficie activa.
La quimiossorción disociativa de agua en estos sitios es clave para la reactividad observada.
Este hallazgo pone de relieve que no todas las reacciones de racimo de metales se adhieren a las restricciones del modelo de caparazón electrónico.

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