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Efectos de ligando axial en las estructuras geométricas y electrónicas de los complejos de oxohierro no hemo (IV)
Timothy A Jackson1, Jan-Uwe Rohde, Mi Sook Seo
1Department of Chemistry and Center for Metals in Biocatalysis, 207 Pleasant Street S.E., University of Minnesota, Minneapolis, Minnesota 55455, USA.
Journal of the American Chemical Society
|August 21, 2008
Resumen
Este estudio sintetizó nuevos complejos de oxoirón (IV) con diferentes ligandos trans, revelando cómo estos ligandos alteran significativamente las características espectroscópicas de la unidad hierro-oxo. Los cálculos de la teoría funcional de la densidad aclararon los mecanismos electrónicos detrás de estos cambios espectroscópicos observados.
Área de la Ciencia:
- Química Inorgánica La Química Inorgánica es la química inorgánica.
- Química bioorgánica Química bioorgánica.
- Química computacional es la química computacional.
Sus antecedentes:
- Los complejos de oxoirón no hemo (IV) son intermediarios cruciales en las reacciones de oxidación biológica.
- El ligando de tetrametilciclam (TMC) proporciona un andamio estable para estudiar las propiedades electrónicas del núcleo de oxohierro (IV).
- Comprender la influencia de los ligandos axiales en el enlace Fe=O es clave para dilucidar los mecanismos de reacción.
Objetivo del estudio:
- Para sintetizar y caracterizar una serie de S=1 complejos de oxoirón (IV) con diferentes transligandos (X).
- Investigar el impacto de estos transligantes en las propiedades espectroscópicas de la unidad Fe (IV) = O.
- Para dilucidar los mecanismos electrónicos responsables de las variaciones espectroscópicas observadas utilizando métodos computacionales.
Principales métodos:
- Síntesis de complejos [Fe (IV) (O) (TMC) (X) ] (+) mediante la reacción de [Fe (IV) (O) (TMC) (NCMe) ] (2+) con sales de NR4X.
- Caracterización mediante absorción electrónica, absorción de rayos X de borde Fe K, resonancia Raman y espectroscopia de Mossbauer.
- Análisis computacional utilizando la teoría funcional de densidad (DFT) y DFT dependiente del tiempo (TD-DFT).
Principales resultados:
- Se sintetizó con éxito una serie de complejos S=1 oxoirón ((IV) con diferentes ligandos trans (X = OH ((-), CF3CO2 ((-), N3 ((-), NCS ((-), NCO ((-), CN ((-)).
- Las características espectroscópicas (absorción cercana al IR, pre-borde de absorción de rayos X, división cuádrupolar de Mossbauer) mostraron una fuerte dependencia del ligando trans.
- Las longitudes de enlace Fe=O se mantuvieron en gran medida consistentes, mientras que el DFT reveló la modulación de las orbitales antienlace Fe=O por parte de los transligantes.
Conclusiones:
- La identidad del transligando influye significativamente en la estructura electrónica y las propiedades espectroscópicas de la unidad S=1 oxoirón (IV).
- Los cálculos de DFT predicen con precisión las observaciones experimentales y revelan las interacciones orbitales que rigen estos cambios.
- Se asignaron transiciones de transferencia de carga para ligandos específicos, lo que explica la mejora de resonancia Raman del modo Fe=O.
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