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Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR
Published on: December 16, 2013
Estructuras moleculares e investigaciones espectroscópicas por resonancia magnética de complejos de porfirinato de
H Ogura1, L Yatsunyk, C J Medforth
1Department of Chemistry, University of Arizona, Tucson, AZ 85721-0041, USA.
Journal of the American Chemical Society
|July 6, 2001
Resumen
Este estudio detalla nuevos complejos de porfirina de hierro (III) con ligandos axiales, revelando conocimientos estructurales y comportamientos dinámicos a través de la espectroscopia. Estos hallazgos avanzan en la comprensión de los sistemas de porfirina estéricamente obstaculizados.
Área de la Ciencia:
- Coordinación Química de la Coordinación
- Química organometálica Química orgánica de los metales.
- Ciencia de los materiales Ciencia de los materiales.
Sus antecedentes:
- Los complejos de porfirina de hierro (III) son cruciales en varios procesos catalíticos y biológicos.
- Comprender la influencia de los ligandos axiales en la conformación y dinámica del macrociclo de la porfirina es clave.
- El obstáculo estérico de los ligandos axiales puede alterar significativamente la estructura compleja y la reactividad.
Objetivo del estudio:
- Para sintetizar y caracterizar nuevos complejos de hierro ligado bis-axialmente (III) octaetiltetrafenilporfirina (OETPP) Fe (III).
- Investigar las propiedades estructurales, electrónicas y dinámicas de estos complejos utilizando cristalografía y espectroscopia de rayos X.
- Para dilucidar la relación entre el ligando axial, el volumen estérico y la conformación y dinámica del macrociclo de la porfirina.
Principales métodos:
- Síntesis de tres complejos OETPPFe ((III) ligados bis-axialmente con N-metillimidazol, 4- ((dimetilamino) piridina y 2-metillimidazol.
- Cristalografía de rayos X para determinar las estructuras moleculares y cristalinas precisas.
- Espectroscopia de resonancia paramagnética de electrones (EPR) y resonancia magnética nuclear (RMN) (1D y 2D) para la caracterización electrónica y dinámica.
Principales resultados:
- Las estructuras cristalinas revelan conformaciones de macrociclo ensillado, con la orientación del ligando influenciada por las interacciones estéricas.
- Las longitudes de enlace Fe-N axial son más largas en el complejo bis-(2-metilimidazol) en comparación con las especies relacionadas.
- Los datos espectroscópicos indican un comportamiento dinámico complejo, que incluye la inversión del sillín y la rotación del ligando, con variaciones dependientes de la temperatura.
Conclusiones:
- La masa estérica de los ligandos axiales tiene un impacto significativo en la conformación del macrociclo OETPP y la orientación de los ligandos.
- Los complejos preparados exhiben un comportamiento fluxional, con inversión de la silla de montar y rotación de ligandos que ocurren incluso a bajas temperaturas.
- El estudio proporciona información valiosa sobre las relaciones estructura-dinámica-propiedad en sistemas de porfirina estéricamente exigentes.
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