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La polarización inducida por parahidrógeno por catálisis de reemplazo en pares en las nanopartículas Pt e Ir
Ronghui Zhou1, Evan W Zhao, Wei Cheng
1Department of Chemistry and ‡Department of Chemical Engineering, University of Florida , Gainesville, Florida 32611, United States.
Journal of the American Chemical Society
|January 29, 2015
Resumen
Los catalizadores metálicos soportados producen inesperadamente señales de polarización inducida por parahidrógeno (PHIP) en las reacciones de hidrogenación. Este descubrimiento permite nuevos métodos de hiperpolarización para aplicaciones biomédicas utilizando polarización inducida por parahidrógeno.
Área de la Ciencia:
- La catálisis por catálisis.
- Química orgánica es la química orgánica.
- Espectroscopia de RMN y RMN.
Sus antecedentes:
- Los procesos de adición en pares y aleatorios son típicamente indistinguibles en la hidrogenación.
- La polarización inducida por parahidrógeno (PHIP) se basa en la correlación de espín, lo que hace que las interacciones de la superficie del catalizador sean cruciales.
- No se esperaba que los catalizadores metálicos apoyados facilitaran PHIP debido a la rápida difusión del átomo H y el mecanismo de Horiuti-Polanyi.
Objetivo del estudio:
- Para investigar la sorprendente observación de señales detectables de RMN de PHIP utilizando catalizadores de hidrogenación de metales con soporte.
- Demostrar que las nanopartículas Pt e Ir soportadas pueden catalizar reacciones de reemplazo en pares en alquenos específicos.
- Explorar el potencial del PHIP de reemplazo en pares para hiperpolarizar diversos sustratos para uso biomédico.
Principales métodos:
- Utilizando nanopartículas de platino (Pt) e iridio (Ir) soportadas como catalizadores.
- Mezclas fluidas de parahidrógeno y alquenos (propeno, 3,3,3-trifluoropropeno) sobre los catalizadores.
- Empleando simulaciones espectrales de matriz de densidad para analizar la estereoselectividad de la reacción y confirmar el mecanismo de reemplazo en pares.
Principales resultados:
- Se demostró que las nanopartículas Pt e Ir soportadas catalizan el reemplazo en pares del propeno y el 3,3,3-trifluoropropeno.
- Se generaron intensas señales de RMN de PHIP en los sustratos de alqueno mediante la incorporación del orden de giro del parahidrógeno.
- La estereoselectividad del mecanismo de reemplazo en pares se reveló con éxito a través de simulaciones espectrales.
Conclusiones:
- Los catalizadores metálicos con soporte pueden, de hecho, producir señales detectables de RMN PHIP, contrariamente a las expectativas anteriores.
- La sustitución por pares en nanopartículas soportadas ofrece una nueva ruta para la hiperpolarización.
- Este método tiene un potencial significativo para ampliar la gama de sustratos utilizables para PHIP en imágenes y diagnósticos biomédicos.
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