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Arreglos de cromóforos conjugados con un agujero inusualmente grande polaron deslocalización longitudes de largo
Kimihiro Susumu1, Paul R Frail, Paul J Angiolillo
1Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323, USA.
Journal of the American Chemical Society
|June 29, 2006
Resumen
Estudiamos los estados de los radicales catiónicos en los oligómeros de porfirina (PZnn) de zinc (II) utilizando la espectroscopia EPR. Estos materiales exhiben una deslocalización de polarón de agujero sin precedentes y de temperatura invariable, verificando un modelo de salto de carga a grandes distancias.
Área de la Ciencia:
- Ciencia de los materiales Ciencia de los materiales.
- La espectroscopia es una técnica de espectroscopia.
- Electrónica orgánica y electrónica orgánica.
Sus antecedentes:
- Se investigan los oligómeros de porfirina (PZnn) de zinc ((II) puenteado de etina meso-a-meso por sus propiedades electrónicas.
- Comprender la deslocalización de carga en estos sistemas conjugados extendidos es crucial para el desarrollo de nuevos materiales electrónicos.
Objetivo del estudio:
- Para investigar la deslocalización del portador de carga en los estados radicales catiónicos de los oligómeros PZnn utilizando la espectroscopia de resonancia paramagnética de electrones (EPR) de banda X de temperatura variable.
- Para determinar la escala de longitud y la dependencia de temperatura de la deslocalización del agujero polaron.
Principales métodos:
- Se realizó una espectroscopia EPR de banda X a temperatura variable (4298 K) en oligómeros de PZnn ([PZn2-PZn7]+).
- El análisis de los anchos de línea EPR (DeltaBp-p) se utilizó para cuantificar la deslocalización polaron del agujero.
- Los datos fueron modelados utilizando un modelo estocástico, unidimensional de salto de carga.
Principales resultados:
- Los oligómeros PZnn+ exhibieron las longitudes de deslocalización de polarones de agujero más grandes medidas hasta la fecha, extendiéndose hasta aproximadamente 75 Å.
- Se encontró que la longitud de deslocalización de carga era invariante con la temperatura en el rango estudiado.
- Los datos experimentales de EPR apoyaron fuertemente un mecanismo de deslocalización de agujero tipo Norris.
Conclusiones:
- Los oligómeros de PZnn demuestran un robusto mecanismo de deslocalización de agujero en escalas de longitud significativas, desafiando las teorías convencionales de localización de carga.
- Los hallazgos sugieren que las bajas energías de reorganización de la esfera interna en los bloques de construcción poliméricos son clave para lograr una larga deslocalización de polarones en materiales electrónicos avanzados.
- Las tasas de salto de polaron en estos oligómeros son excepcionalmente altas, superando 10^7 s^-1 incluso a bajas temperaturas.
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