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Auto-reconocimiento entre diferentes macroiones polipróticos durante los procesos de ensamblaje en una solución
Tianbo Liu1, Melissa L K Langston, Dong Li
1Department of Chemistry, Lehigh University, Bethlehem, PA 18015, USA. liu@lehigh.edu
Science (New York, N.Y.)
|March 26, 2011
Resumen
Dos tipos de macroiones de óxido metálico, los Kepleratos, se autoensamblan en estructuras distintas en solución. Esta separación de fase se produce debido a las diferencias en la densidad de carga durante el ensamblaje, no a la estructura de la superficie.
Área de la Ciencia:
- Química supramolecular de las moléculas.
- Ciencia de los materiales Ciencia de los materiales.
- Nanotecnología La nanotecnología es la nanotecnología.
Sus antecedentes:
- Los macroiones basados en óxidos metálicos, conocidos como Kepleratos, son especies neutrales en forma cristalina.
- Estos macroiones poseen una estructura definida: [(enlace) 30(pentagono) 12) [{M(H2O)} 30{(Mo) Mo5} 12 , donde M puede ser Fe (III) o Cr (III).
Objetivo del estudio:
- Para investigar el auto-reconocimiento y el comportamiento de ensamblaje de dos diferentes macroiones de Keplerato en una solución acuosa diluida.
- Comprender las fuerzas motrices detrás de la formación de superestructuras a partir de mezclas de estos macroniones.
Principales métodos:
- Preparación de soluciones acuosas diluidas homogéneas de dos macroiones de Keplerato distintos (Fe (III) y Cr (III)).
- Observación de los procesos de ensamblaje, específicamente la dimero-oligomerización, bajo condiciones deprotonadas.
- Análisis de la formación de superestructuras en mezclas de los dos macroiones.
Principales resultados:
- A pesar de las estructuras geométricas superficiales idénticas, las mezclas de Fe (III) y Cr (III) Kepleratos forman superestructuras homogéneas, no especies mixtas.
- La separación de fases es impulsada por diferencias en las densidades de carga macroiónica durante la formación lenta de dímeros/oligómeros.
- Se observaron marcadas diferencias en los tiempos de residencia de los ligandos de agua superficial y la movilidad del agua interfacial entre los Kepleratos Cr (III) y Fe (III).
Conclusiones:
- Un fenómeno de auto-reconocimiento gobierna el ensamblaje de estos Kepleratos, lo que lleva a la formación de superestructuras selectivas.
- La densidad de carga macroiónica, influenciada por el tipo de metal (Fe vs. Cr), es el factor clave en la separación de fases.
- Las diferencias en la dinámica del agua interfacial juegan un papel importante en el auto-reconocimiento observado.
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