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Relé de protones en una cadena unidimensional de enlaces de hidrógeno compuesta por moléculas de agua y un derivado
1Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, Meguro, Tokyo 153-8902, Japan.
Journal of the American Chemical Society
|October 25, 2001
Resumen
Este estudio revela la migración de protones en los cristales de tetrahidrato de bifenilo (BSQB*4H2O). Un mecanismo de relé de protones dentro de los grupos de agua facilita la migración solitónica a lo largo de cadenas enlazadas por hidrógeno.
Área de la Ciencia:
- Ingeniería de Cristal Ingeniería de Cristal.
- Química supramolecular de las moléculas.
- Ciencia de los materiales Ciencia de los materiales.
Sus antecedentes:
- El bis ((squaryl) biphenyl (BSQB) es una molécula con potencial para crear redes funcionales de enlaces de hidrógeno.
- Los cristales hidratados ofrecen entornos únicos para estudiar la dinámica de los protones y las interacciones moleculares.
Objetivo del estudio:
- Para caracterizar la estructura cristalina y la dinámica del bifenilo hidratado (BSQB*4H2O).
- Para investigar el mecanismo de transporte de protones dentro de las cadenas unidimensionales de enlaces de hidrógeno.
- Para correlacionar las características estructurales con las propiedades dieléctricas observadas.
Principales métodos:
- Análisis cristalográfico de rayos X para determinar la estructura cristalina y la disposición molecular.
- Espectroscopia de RMN de deuterio giratoria de ángulo mágico de estado sólido para sondear el intercambio y la migración de deuterio.
- Mediciones de dieléctricos de CA para analizar procesos dinámicos y permisividad dependiente de la frecuencia.
Principales resultados:
- BSQB existe como un dianión, con una protonación parcial de las moléculas de agua en BSQB*4H2O.
- Intercambio de deuterio y migración observada en BSQB*4D2O alrededor de 250 K, lo que indica movilidad de protones.
- Aumento significativo de la permitividad dieléctrica por encima de 250 K, relacionado con el relé de protones y la migración solitónica.
Conclusiones:
- Un mecanismo de relé de protones que involucra grupos de agua y el dianión BSQB facilita el transporte de carga.
- La migración solitónica de los límites de dominio cargados ocurre a lo largo de la cadena unidimensional de enlaces de hidrógeno.
- El estudio aclara un nuevo mecanismo para el transporte de protones en cristales orgánicos hidratados.
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