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La notable labilidad axial de los complejos de corroles de hierro (III) es notable
Crisjoe A Joseph1, Peter C Ford
1Department of Chemistry and Biochemistry, University of California-Santa Barbara, Santa Barbara, CA 93106-9510, USA.
Journal of the American Chemical Society
|May 5, 2005
Resumen
La fotólisis instantánea de los complejos de corrolato de hierro (III) libera óxido nítrico (NO), que reforma rápidamente el complejo. El ligando corrolato rico en electrones y el estado de hierro triple aceleran la recombinación de NO, mostrando interacciones débiles de la base de Lewis.
Área de la Ciencia:
- Química Inorgánica La Química Inorgánica es la química inorgánica.
- La fotoquímica es la fotoquímica.
- Coordinación Química de la Coordinación
Sus antecedentes:
- Los ligandos corrolados son ligandos macrocíclicos conocidos por sus fuertes propiedades donantes de electrones.
- Los complejos de hierro (III) con ligandos corrolatos exhiben configuraciones electrónicas únicas, incluidos los posibles estados base triplet.
- La ligadura del óxido nítrico (NO) a los centros metálicos es crucial en varios procesos químicos y biológicos.
Objetivo del estudio:
- Para investigar la fotolabilidad del óxido nítrico (NO) de los complejos de corrolato de hierro (III) nitrosil.
- Para determinar la cinética de la reunión del NO al centro del hierro después de la fotólisis flash.
- Para dilucidar la influencia de las propiedades electrónicas del ligando corrolado y las bases de Lewis en la dinámica de unión de NO.
Principales métodos:
- La fotólisis de flash se empleó para inducir la labilización de NO de los complejos de corrolato de hierro (III) nitrosil.
- Se utilizó espectroscopia con resolución de tiempo para monitorear la rápida recombinación de NO al centro del hierro.
- Se realizaron estudios cinéticos con diferentes concentraciones de bases de Lewis (solventes y piridina) para determinar las constantes de velocidad y las constantes de equilibrio.
Principales resultados:
- La fotólisis instantánea de los corolatos de hierro (III) de nitrosilo dio lugar a una rápida liberación de NO seguida de una rápida reconexión.
- Las constantes de velocidad de segundo orden para la reconexión de NO (kNO) fueron excepcionalmente altas, comparables a las de los análogos de la porfirina ferrosa, atribuidas al ligando corrolado donante de electrones y al estado de hierro triple (III).
- La unión del ligando axial se debilitó significativamente, con un impacto mínimo de las bases suaves de Lewis como la piridina, lo que indica una baja afinidad del centro metálico para las bases de Lewis.
Conclusiones:
- La configuración de ligando corrolado y hierro triple (III) que dona fuertemente electrones reduce drásticamente la afinidad del centro metálico por los ligandos axiales.
- Esta interacción débil de la base de Lewis facilita una cinética de reunión de NO extremadamente rápida, incluso en presencia de disolventes coordinadores.
- El estudio destaca las propiedades electrónicas únicas de los complejos de corrolato de hierro y sus implicaciones para el control de la dinámica de NO.
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