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La conductividad de salto en los cables moleculares exhibe un gran efecto de isótopos cinéticos de átomos pesados

Quyen Van Nguyen¹, C Daniel Frisbie¹

¹Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, United States.

Journal of the American Chemical Society

|February 15, 2021

Resumen

Descubrimos un gran efecto de isótopo cinético (KIE) en el transporte de carga a través de largos cables orgánicos. Este hallazgo sugiere un nuevo mecanismo para el movimiento de electrones en la electrónica molecular.

Área de la Ciencia:

La electrónica molecular
Los fenómenos de transporte cuántico
Física de los semiconductores orgánicos

Sus antecedentes:

El transporte de carga intramolecular es crucial para la electrónica molecular.
Los efectos de isótopos cinéticos (KIE) son sondas sensibles de los mecanismos de reacción y las vías de transporte.
La comprensión del transporte de carga en moléculas conjugadas π es clave para el desarrollo de nuevos dispositivos electrónicos.

Objetivo del estudio:

Investigar el mecanismo de transporte de carga intramolecular en las moléculas de oligfenilenimina (OPI).
Para cuantificar el efecto del isótopo cinético (KIE) en la conductividad de los cables moleculares OPI.
Para aclarar el papel de la sustitución isotópica en la modulación de las propiedades de transporte de carga.

Principales métodos:

Fabricación de cables moleculares OPI conectados a electrodos de oro.
Síntesis de moléculas OPI etiquetadas isotópicamente (utilizando C y N).
Medición de la conductividad y de la conductividad dependiente de la temperatura de los cables OPI con y sin etiquetado isotópico.

Principales resultados:

Se observó un KIE grande (∼2,7 por átomo etiquetado) para los cables OPI largos (> 4 nm).
No se observó un KIE significativo para los cables OPI más cortos (< 4 nm), lo que indica un mecanismo de túnel directo.
La conductividad en cables OPI largos y etiquetados con N mostró un comportamiento activado con la temperatura.

Conclusiones:

Los grandes KIE en los largos cables OPI sugieren un mecanismo de túnel polaron asistido térmicamente a través de la barrera.
La ausencia de KIE en cables cortos apoya un modelo de túnel directo.
La observación de grandes KIE de conductividad proporciona una herramienta poderosa para comprender los mecanismos de transporte de carga en los sistemas moleculares.

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