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Complejos de hierro de ligandos cuadrados de tipo tetradentado polipirídico como catalizadores para la oxidación del

Lanka D Wickramasinghe¹, Rongwei Zhou¹, Ruifa Zong¹

¹Department of Chemistry, 112 Fleming Building, University of Houston , Houston, Texas 77204-5003, United States.

Journal of the American Chemical Society

|October 2, 2015

Resumen

El nuevo ligando tetradentado, 2- ((pyrid-2'-yl) -8- ((1′′,10′′-phenanthrolin-2′′-yl) -quinolina (ppq), facilita la oxidación eficiente del agua. El complejo de hierro (III) -ppq cataliza la evolución del oxígeno con una alta frecuencia de rotación.

Área de la Ciencia:

Química de coordinación
Química bioorgánica
Catálisis

Sus antecedentes:

El ligando tetradentado 2- ((pyrid-2'-yl) -8- ((1′′,10′′-phenanthrolin-2′′-yl) -quinolina (ppq) tiene una columna vertebral única de cuaterpiridina con un enlace de carbono sp ((2).
Esta estructura crea un entorno de coordinación plano cuadrado neutro adecuado para los metales de transición de primera fila.
Se sintetizaron y caracterizaron complejos de hierro con ppq y amina bis-fenantrolina (dpa).

Objetivo del estudio:

Investigar las propiedades electroquímicas y la actividad catalítica de los complejos de hierro con ligandos ppq y dpa.
Para comparar las capacidades de oxidación del agua de los complejos de hierro mononucleares y dinucleares.
Para explorar el mecanismo de la evolución del oxígeno catalizado por estos complejos de hierro.

Principales métodos:

Síntesis y análisis estructural de rayos X de complejos de hierro (III) con ppq y dpa.
Estudios electroquímicos para determinar los potenciales de oxidación y los procesos de transferencia de electrones.
Experimentos catalíticos en los que se utiliza el nitrato de amonio cerico como oxidante sacrificial para medir las tasas de evolución del oxígeno y las frecuencias de rotación.

Principales resultados:

El complejo Fe ((III) ((ppq) forma un dímero con puente μ-oxo, mientras que Fe ((III) ((dpa) forma un complejo 1:1.
Fe (III) (dpa) exhibe dos ondas de oxidación reversibles de un electrón.
Fe ((III) ((ppq) muestra un proceso de oxidación de dos electrones, indicativo de estados de oxidación más altos (Fe ((IV) Fe ((IV) a Fe ((V) Fe ((III))), y la posterior desproporción a una especie FeO.
El complejo Fe (III) (ppq) demostró una actividad de evolución de oxígeno significativamente mayor (TOF = 7920 h−1) en comparación con el complejo Fe (III) (dpa) (TOF = 842 h−1) en condiciones ácidas con un oxidante sacrificial.

Conclusiones:

El ligando ppq permite propiedades electrónicas únicas en sus complejos de hierro, facilitando procesos redox de múltiples electrones.
El complejo dinuclear Fe ((III) ((ppq) es un catalizador altamente eficiente para la oxidación del agua, superando significativamente al complejo mononuclear Fe ((III) ((dpa).
Estos hallazgos destacan el potencial del diseño de ligandos a medida en el desarrollo de catalizadores avanzados para fotosíntesis artificial y aplicaciones de división de agua.

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