Una nueva manera de romper el agua en hidrógeno y oxígeno/New way to split water into hydrogen and oxygen

El diseño de sistemas eficientes para romper el agua en hidrógeno y oxígeno mediante la luz solar, es uno de los desafíos más importantes para la ciencia actual, dado el potencial a largo plazo del hidróegno como combustible limpio y sostenible. Pero los sistemas desarrolaldos hasta ahora por el hombre son muy poco eficientes y a menudo precisan del uso reactivos químicos adicionales.
La nueva vía diseñada recientemente por David Milstein y sus colegas del Departamento de Química Orgánica del Instituto Weizmann, se divide en una serie de reacciones que conducen a la liberación de hidróegno y oxígeno en etapas concescutivas gobernadas por el calor y luz, por medio del uso de un complejo de Rutenio, que el equipo de Milstein había diseñado en anteriores estudios. El complejo se regenera al final y puede ser reciclado y reutilizado.

The design of efficient systems for splitting water into hydrogen and oxygen, driven by sunlight is among the most important challenges facing science today, underpinning the long term potential of hydrogen as a clean, sustainable fuel. But man-made systems that exist today are very inefficient and often require additional use of sacrificial chemical agents.
The new approach that David Milstein and colleagues of the Weizmann Institute’s Organic Chemistry Department, has recently devised is divided into a sequence of reactions, which leads to the liberation of hydrogen and oxygen in consecutive thermal- and light-driven steps, mediated by a ruthenium complex that Milstein’s team designed in previous studies. The complex is at last regenerated so it can be recycled and used again.

Tomado de/ Taken from Science Daily

Resumen de la publicación científica/Abstract of the research paper
Science 3 April 2009, Vol. 324. no. 5923, pp. 74-77,DOI: 10.1126/science.1168600

Consecutive Thermal H2 and Light-Induced O2 Evolution from Water Promoted by a Metal Complex
Stephan W. Kohl, Lev Weiner, Leonid Schwartsburd, Leonid Konstantinovski, Linda J. W. Shimon, Yehoshoa Ben-David, Mark A. Iron, David Milstein1
Discovery of an efficient artificial catalyst for the sunlight-driven splitting of water into dioxygen and dihydrogen is a major goal of renewable energy research. We describe a solution-phase reaction scheme that leads to the stoichiometric liberation of dihydrogen and dioxygen in consecutive thermal- and light-driven steps mediated by mononuclear, well-defined ruthenium complexes. The initial reaction of water at 25°C with a dearomatized ruthenium (II) [Ru(II)] pincer complex yields a monomeric aromatic Ru(II) hydrido-hydroxo complex that, on further reaction with water at 100°C, releases H2 and forms a cis dihydroxo complex. Irradiation of this complex in the 320-to-420–nanometer range liberates oxygen and regenerates the starting hydrido-hydroxo Ru(II) complex, probably by elimination of hydrogen peroxide, which rapidly disproportionates. Isotopic labeling experiments with H2 17-O and H2 18-O show unequivocally that the process of oxygen–oxygen bond formation is intramolecular, establishing a previously elusive fundamental step toward dioxygen-generating homogeneous catalysis.