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Espectroscopia 2D ultrarrápida del exceso de protones en el agua líquida

Martin Thämer¹, Luigi De Marco², Krupa Ramasesha³

¹Department of Chemistry, Institute for Biophysical Dynamics, and James Franck Institute, The University of Chicago, Chicago, IL 60637, USA.

Science (New York, N.Y.)

|October 3, 2015

Resumen

Investigando la transferencia de protones en el agua utilizando espectroscopia infrarroja bidimensional ultrarrápida (2D IR), este estudio revela que el complejo de Zundel, H2O2+, juega un papel clave. Se determinó que la vida útil del complejo Zundel era de al menos 480 femtosegundos.

Área de la Ciencia:

Química Física
Espectroscopia
Dinámica Química

Sus antecedentes:

La transferencia de protones en soluciones acuosas es fundamental para muchos procesos químicos y biológicos.
Las estructuras y dinámicas precisas de las especies de agua protonadas siguen siendo difíciles de dilucidar.
El complejo de Zundel, H2O2+, es un intermediario propuesto en el transporte acuoso de protones.

Objetivo del estudio:

Investigar las estructuras y la dinámica del exceso de protones en soluciones acuosas.
Caracterizar el complejo de Zundel y su papel en los mecanismos de transferencia de protones.
Para determinar el tiempo de vida del complejo Zundel en ácido clorhídrico acuoso.

Principales métodos:

Se empleó espectroscopia de infrarrojos bidimensional (2D IR) ultrarrápida.
Las vibraciones de estiramiento O-H fueron excitadas para sondear la dinámica de protones.
Se analizaron las respuestas espectrales del infrarrojo medio, incluidos los picos cruzados de estiramiento y flexión.

Principales resultados:

Se observó la interacción entre las vibraciones de estiramiento y flexión de las moléculas de agua flanqueantes en el complejo de Zundel.
Se identificaron frecuencias características para la interacción estiramiento- flexión del complejo de Zundel en 3200 cm (-1) y 1760 cm (-1).
Un límite inferior para la vida útil del complejo de Zundel se determinó como 480 femtosegundos basado en desplazamientos espectrales dependientes del tiempo.

Conclusiones:

El complejo de Zundel, H2O2+, es una especie significativa en la transferencia acuosa de protones.
La dinámica observada proporciona información sobre el mecanismo de interconversión de protones en el agua.
La espectroscopia infrarroja 2D ultrarrápida es una herramienta poderosa para estudiar especies transitorias en solución.

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