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El espín histérico y la deslocalización de carga en un conductor molecular basado en fenalenilo
Sushanta K Pal1, Pradip Bag, Arindam Sarkar
1Department of Chemistry, University of California, Riverside, California 92521-0403, USA.
Journal of the American Chemical Society
|November 18, 2010
Resumen
Este estudio revela dos estados electrónicos distintos en un radical fenalenilo sustituido por butilo que exhibe una transición de fase. La distancia interplanar π-π dentro de los dímeros es clave para sus propiedades histéricas.
Área de la Ciencia:
- Química del estado sólido.
- Ciencia de los materiales ciencia de los materiales.
- La electrónica orgánica es la electrónica orgánica.
Sus antecedentes:
- Los radicales neutros a base de fenalenilo son de interés por sus propiedades electrónicas.
- Las transiciones de fase histéricas en materiales orgánicos pueden conducir a estados bistables.
- Comprender las relaciones estructura-propiedad es crucial para el diseño de materiales funcionales.
Objetivo del estudio:
- Investigar la estructura electrónica en estado sólido y las propiedades de un radical fenalenil sustituido por butilo (3).
- Para analizar la distribución de la densidad de electrones e identificar estados electrónicos distintos dentro del bucle de histeresis.
- Para aclarar los factores estructurales responsables de la observación de la transición de la fase histérica.
Principales métodos:
- Difracción de rayos X de estado sólido para analizar estructuras cristalinas a varias temperaturas.
- Espectroscopia de transmitancia infrarroja (IR) para sondear los estados electrónicos.
- Análisis cuantitativo de la distribución de la densidad de electrones.
- Estudio comparativo con un radical relacionado sustituido por etil (1).
Principales resultados:
- Identificó dos estados electrónicos distintos dentro del bucle de histeresis del radical 3.
- Bistabilidad observada de estos estados electrónicos a través de la transmitancia IR.
- Determinó que los cambios en la distancia interplanar π-π dentro de los dímeros son críticos para las propiedades físicas.
- Se encontró que las interacciones C-H···π y la redistribución del espín no causan la histeresis.
Conclusiones:
- La transición de fase histérica en el radical 3 se rige principalmente por cambios en las distancias interplanares π-π.
- El estado de alta temperatura durante el enfriamiento es termodinámicamente estable.
- El estado de baja temperatura durante el calentamiento es cinéticamente atrapado por una gran barrera de energía (> 100 kJ / mol) debido al movimiento de anillo de gran amplitud y la reorganización de la red.
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