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Interconversión de dióxido/peróxido de hidrógeno utilizando parejas redox de porfirinas e isoflorinas distorsionadas
Wataru Suzuki1, Hiroaki Kotani1, Tomoya Ishizuka1
1Department of Chemistry, Faculty of Pure and Applied Sciences , University of Tsukuba and CREST (JST) , 1-1-1 Tennoudai , Tsukuba , Ibaraki 305-8571 , Japan.
Journal of the American Chemical Society
|March 19, 2019
Resumen
Los investigadores lograron la primera conversión reversible entre el dioxígeno (O2) y el peróxido de hidrógeno (H2 O2) utilizando una nueva porfirina dimetilada. Este avance permite una eficiente interconversión O2/H2, crucial para las aplicaciones energéticas.
Área de la Ciencia:
- Química supramolecular
- Catálisis
- Almacenamiento de energía
Sus antecedentes:
- El peróxido de hidrógeno (H2 O2) es cada vez más importante como fuente de energía.
- Es muy deseable una interconversión eficiente entre el dioxígeno (O2) y el H2.
- Los estudios anteriores se centraron en la conversión de O2 a H2 O2, sin sistemas reversibles.
Objetivo del estudio:
- Para lograr la primera interconversión reversible O2/H2.
- Investigar el papel de la estructura de la porfirina en el control de la reversibilidad.
- Para comprender el mecanismo de conversión reversible O2/H2 O2.
Principales métodos:
- Síntesis de N21, N23-dimetilado porfirina distorsionada en la silla de montar y su forma reducida (isoflorina).
- Ciclo repetido de la interconversión O2/H2 a través de burbujas de gas alternas (Ar/O2).
- Análisis cinético y termodinámico utilizando RMN H, espectroscopia UV-vis y cálculos DFT.
Principales resultados:
- Demostración exitosa de la interconversión reversible O2/H2 utilizando el sistema de porfirina dimetilado.
- El isómero estructural (N21, N22-dimetilado porfirina) no mostró conversión reversible, destacando la importancia del posicionamiento del grupo metilo.
- Se logró minimizar la diferencia de energía libre de Gibbs y la energía de activación a través de la N-metilación, lo que permite una interconversión eficiente.
Conclusiones:
- El sistema de porfirina N21, N23-dimetilado permite una conversión reversible de O2/H2 sin precedentes.
- La dirección interna del protón N-H y la orientación del par solitario son críticas para la formación de enlaces de hidrógeno y la reversibilidad de la reacción.
- Se propone un adducto de enlace de hidrógeno de dos puntos entre la porfirina y H2O2 como intermediario clave.
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