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Cambiabilidad magnética a temperatura ambiente asistida por tautomerismo de valencia histérica en un marco de
Anthony Lannes1, Yan Suffren2, Jean Bernard Tommasino1
1Univ Lyon, Université Claude Bernard Lyon 1, Laboratoire des Multimatériaux et Interfaces, UMR CNRS 5615, F-69622, Villeurbanne, France.
Journal of the American Chemical Society
|December 13, 2016
Resumen
Un nuevo polímero de coordinación de manganeso exhibe un cambio de valencia único impulsado por la temperatura cerca de la temperatura ambiente. Esta transición implica la oxidación del manganeso y la reducción radical, creando formas distintas de alta y baja temperatura.
Área de la Ciencia:
- Química de coordinación
- Ciencias de los materiales
- El magnetismo
Sus antecedentes:
- Los compuestos de manganeso-nitrónico-nitróxido son conocidos por sus interesantes propiedades magnéticas.
- El tautomerismo de valencia es un fenómeno en el que una molécula puede existir en diferentes estados electrónicos.
- Los polímeros de coordinación ofrecen estructuras sintonizables para explorar nuevos comportamientos electrónicos.
Objetivo del estudio:
- Para investigar la inusual transición tautomérica de valencia inducida por térmica en un polímero de coordinación 2D de manganeso-nitronilo-óxido.
- Caracterizar los cambios estructurales y electrónicos asociados a esta transición.
- Comprender el mecanismo y la dependencia de la temperatura del tautomerismo de valencia.
Principales métodos:
- Mediciones de la susceptibilidad magnética dependientes de la temperatura.
- Calorimetría por barrido diferencial (DSC).
- Difracción de rayos X de un solo cristal.
- Espectroscopía de absorción UV-V.
- Espectroscopias de absorción de rayos X y de emisión de rayos X.
- Espectroscopia de resonancia paramagnética de electrones (EPR).
Principales resultados:
- El polímero de coordinación {[Mn2(NITIm) 3ClO4}n (1) muestra una transición tautomérica de valencia histérica cerca de la temperatura ambiente.
- La transición implica la oxidación de Mn(II) a Mn(III) y la reducción de los radicales NITIm a NITRed2- al enfriarse (274 K) y se invierte al calentarse (287 K).
- Múltiples técnicas espectroscópicas y calorimétricas confirmaron las distintas fases de alta temperatura (1HT) y baja temperatura (1LT).
Conclusiones:
- El estudio demuestra un raro ejemplo de transición tautomérica de valencia histérica en un polímero de coordinación a base de manganeso.
- Este fenómeno ofrece potencial para el desarrollo de materiales con propiedades magnéticas y electrónicas conmutables.
- La transición observada destaca la interacción entre el estado redox de iones metálicos y el comportamiento del ligando radical en los sistemas de coordinación.
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