AbstractsChemistry

Harness light from the sun is one of the 21st century’s major goals towards the substitution of fossil fuels for a renewable source of energy. Sustainable production of highly energetic molecules using sunlight as energy source can provide a recyclable fuel round the clock. In this regard, hydrogen from water is envisioned as an ideal cofactor as this energetic store. Viable production of solar fuels will require the use of earth-abundant based catalysts with high activity and efficiency. Long ago, Nature figured out how to take advantage of the sunlight by converting solar energy into chemical bonds, through water and carbon dioxide. This process has been perfected during millions of years and the development of an artificial system to replicate the natural photosynthesis is extremely challenging. Towards the design of these energy conversion schemes based on sunlight, CO2 and H2O, a key step is the water oxidation. The water oxidation provides the electrons needed for the production of fuel. An efficient catalyst is required to overcome the uphill energy multi-electron transformation. The main objective of this thesis is the design of artificial compounds that efficiently oxidizes water into O2, protons and electrons, as the first step towards the exploitation of the sunlight. The study of these complexes could contribute with valuable information about the oxidation mechanisms taking place during the photosynthesis. The results obtained in this thesis firstly show that readily available iron and iridium complexes can carry out the water oxidation in an efficient manner. Homogeneous high valent metal species (IrV/VI, FeV) are the responsible of this redox process. Furthermore, the characterization of a novel oxo-bridged iron-cerium complex constitutes the first direct observation of a heterodimetallic core in a synthetic water oxidation catalyst. These species can be construed as the closest structural and functional model for the essential heterodimetallic MnV–O–CaII center involved in the water oxidation in PSII.; L’aprofitament de la llum solar com a font d’energia és un dels objectius més prometedors alhora de substituir els combustibles fòssils per una font d’energia renovable. La producció sostenible de molècules energètiques mitjançant la llum del sol pot proporcionar un combustible reciclable durant les 24 hores del dia. En aquest aspecte, l’hidrogen obtingut de l’aigua s’entreveu com un cofactor ideal per aquest emmagatzematge energètic. L’ús de catalitzadors basats en materials abundants i amb una activitat i eficiència elevades seran elements indispensables per a la producció viable de combustibles solars. La natura va ser capaç de trobar un mecanisme per aprofitar l’energia solar convertint-la en enllaços químics mitjançant aigua i diòxid de carboni. Aquest procés ha sigut perfeccionat al llarg de milions d’anys i conseqüentment, el desenvolupament de sistemes artificials capaços d’imitar la fotosíntesi natural és extremadament complex. De camí cap al disseny…