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Un imán de una sola molécula de Fe ((III) mononuclear con un cruce de espín de 3/25/2
Susanne Mossin1, Ba L Tran, Debashis Adhikari
1Center for Catalysis and Sustainable Chemistry, Department of Chemistry, Technical University of Denmark, 2800 Lyngby, Denmark. slmo@kemi.dtu.dk
Journal of the American Chemical Society
|July 24, 2012
Resumen
Este estudio revela un complejo de hierro exhibiendo una inesperada transición de espín de S = 3/2 a S = 5/2 por encima de 80 K. Este comportamiento indica que funciona como un solo imán molecular con una barrera de energía definida.
Área de la Ciencia:
- Química Inorgánica La Química Inorgánica es la química inorgánica.
- Ciencia de los materiales Ciencia de los materiales.
- Magnetoquímica es la Magnetoquímica.
Sus antecedentes:
- La síntesis y caracterización de nuevos complejos de hierro son cruciales para el desarrollo de materiales magnéticos avanzados.
- Comprender las transiciones de espín en los complejos de metales de transición es clave para diseñar imanes moleculares con propiedades sintonizables.
Objetivo del estudio:
- Para investigar las propiedades magnéticas y las transiciones de estado de espín del complejo de hierro estable en el aire [(PNP) FeCl(2) ] (1).
- Para dilucidar los factores estructurales y electrónicos que rigen el comportamiento de cruce de espín observado.
Principales métodos:
- Mediciones de susceptibilidad magnética mediante magnetometría SQUID dc y ac.
- Espectroscopia de Mössbauer de temperatura variable y espectroscopia de resonancia paramagnética de electrones (EPR) de banda X.
- Espectroscopia de absorción de rayos X de múltiples bordes (XAS) y difracción de rayos X monocristalino de temperatura variable.
Principales resultados:
- El Complejo 1 exhibe una inesperada transición de giro de S = 3/2 a S = 5/2 por encima de 80 K.
- Los datos de AC SQUID confirman el comportamiento de un solo imán molecular con una barrera activada térmicamente (U(eff) = 32-36 cm(-1)).
- Los datos estructurales y espectroscópicos correlacionan la transición de espín con cambios en la geometría de coordinación del hierro y la estructura electrónica.
Conclusiones:
- El complejo de hierro [{PNP) FeCl{2) ] demuestra un cruce de espín inducido por la temperatura, que funciona como un solo imán molecular.
- La transición de espín observada se atribuye a la proximidad de los estados electrónicos de cuarteto y sexteto, influenciados por las interacciones y la geometría de los ligandos.
- Este trabajo proporciona información sobre los principios de diseño de materiales magnéticos moleculares basados en complejos de hierro.
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