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Comunicación estereocímica eficiente de largo alcance y efectos cooperativos en jaulas Fe4L6 autoensambladas
Naoki Ousaka1, Sergio Grunder, Ana M Castilla
1Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
Journal of the American Chemical Society
|August 25, 2012
Resumen
Los investigadores crearon jaulas de hierro grandes y ópticamente activas (Fe ((4) L ((6)) utilizando aminas quirales y espaciadores. Observaron un equilibrio entre la formación de jaulas y helicatos, con acoplamiento estereoquímico de largo alcance en estructuras más grandes.
Área de la Ciencia:
- Coordinación Química de la Coordinación
- Química supramolecular de las moléculas.
- Materiales Quirales Los materiales quirales son los materiales utilizados para la fabricación de materiales quirales.
Sus antecedentes:
- El autoensamblaje de jaulas metal-orgánicas es un área clave en la química supramolecular.
- El control de la estereoquímica y la topología de estos ensamblajes es crucial para el desarrollo de materiales funcionales avanzados.
- Las jaulas ópticamente activas son de interés para aplicaciones en catálisis y detección enantioselectiva.
Objetivo del estudio:
- Para sintetizar y caracterizar grandes jaulas de coordinación de hierro ópticamente activo (Fe4) (L6).
- Investigar la influencia de la estructura del ligando, específicamente la longitud del espaciador de oligo-p-xileno y el volumen de las aminas quirales, en la formación de la jaula y la estereoquímica.
- Para explorar el fenómeno de acoplamiento estereoquímico de largo alcance en estas estructuras supramoleculares quirales.
Principales métodos:
- Síntesis de ligandos lineales de 5,5'-bis(2-formilpiridinas) con diferentes longitudes de espaciador de oligo-p-xileno (n=0-3).
- Autoensamblaje de jaulas de coordinación de hierro ((II) (Fe ((4) L ((6)) y helicatos (Fe ((2) L ((3)) utilizando aminas quirales.
- Caracterización espectroscópica (por ejemplo, RMN, UV-Vis) y potencialmente cristalografía de rayos X para determinar estructuras y estereoquímica.
- Análisis del comportamiento de la solución para comprender la coexistencia de diferentes arquitecturas supramoleculares.
Principales resultados:
- Preparación exitosa de jaulas de Fe ((4) L ((6) ópticamente activas con espaciadores de ligando sintonizables.
- Observación de un equilibrio entre la jaula de Fe ((4) L ((6) y la formación de helicato de Fe ((2) L ((3), dependiente de la voluminosidad de la amina quiral y la longitud del espaciador.
- Demostración de acoplamiento estereoquímico de largo alcance (>2 nm) entre centros metálicos en jaulas más grandes (n=2, 3), mediado por la rigidez del ligando.
- Evidencia de que la geometría de los ligandos, y no los efectos de engranajes, facilita la comunicación estereocímica.
Conclusiones:
- La masa estérica de aminas quirales y la geometría de ligandos juegan un papel crítico en la dirección del autoensamblaje de los complejos de coordinación del hierro.
- Existe un delicado equilibrio entre la formación de jaulas Fe(4) L(6) y helicatos Fe(2) L(3), influenciados por factores estéricos.
- La comunicación estereoquímica de largo alcance es alcanzable en sistemas supramoleculares extendidos, destacando el potencial para el diseño de arquitecturas quirales complejas.
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