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Espectroscopia de absorción de rayos X polarizada de complejos monocristalinos Mn(V) relevantes para el complejo de

Junko Yano¹, John Robblee, Yulia Pushkar

¹Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA. jyano@lbl.gov

Journal of the American Chemical Society

|October 9, 2007

Resumen

Las especies de manganeso-oxo de alta valencia son cruciales para la división del agua en el fotosistema II. La espectroscopia de absorción de rayos X polarizada reveló estructuras electrónicas distintas para los compuestos de Mn(V) -nitrido y Mn(V) -oxo, lo que ayuda a comprender la oxidación fotosintética del agua.

Área de la Ciencia:

Química Inorgánica La Química Inorgánica es la química inorgánica.
La bioquímica es la bioquímica.
La espectroscopia es una técnica de espectroscopia.

Sus antecedentes:

Las especies de manganeso-oxo de alta valencia están implicadas en la reacción de división del agua del Fotosistema II.
Comprender la estructura electrónica de estos intermediarios es clave para dilucidar el mecanismo de oxidación del agua fotosintética.

Objetivo del estudio:

Investigar la estructura electrónica y las propiedades espectroscópicas de los compuestos mononucleares de cinco y seis coordenadas Mn(V).
Para correlacionar los datos experimentales de espectroscopia de absorción de rayos X (XAS) con los cálculos teóricos de la teoría funcional de la densidad (DFT).

Principales métodos:

Espectroscopia de absorción de rayos X polarizada (XAS) en cristales simples de compuestos de Mn(V) -nitrido y Mn(V) -oxo.
Difracción de rayos X para la alineación de cristales a lo largo de vectores moleculares.
Comparación de los espectros experimentales de la espectroscopia de borde cercano de absorción de rayos X (XANES) con cálculos de DFT y DFT dependientes del tiempo (TD-DFT).

Principales resultados:

Un único pico pre-edge dominante en Mn(V) -nitrido asignado a 3d(z^2) -4p(z) mezclado en un entorno octaédrico distorsionado.
Un pico adicional de baja energía en la pirámide cuadrada Mn(V) -oxo, atribuido a la transición de 1s a 3d(xz,yz) con mezcla de 4p(x,y) debido al desplazamiento de Mn.
Simulación exitosa de los espectros de XANES utilizando TD-DFT.

Conclusiones:

El estudio proporciona información detallada sobre la estructura electrónica de las especies de manganeso de alta valencia.
Se aclararon las firmas espectroscópicas de los compuestos de Mn(V) -nitrido y Mn(V) -oxo.
Estos hallazgos contribuyen a una mejor comprensión del mecanismo de oxidación del agua fotosintética.

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