Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

Periodic Report Summary 1 - COMPUWOC (Computational Modelling and Design of Sustainable Catalysts for Water Oxidation)

This project focuses on the computational study of transition metal complexes catalyzing the oxidation of water. This is a key component of artificial photosynthesis devices, which allow for the clean generation of hydrogen from water and sunlight. The iridium-pyalk, iron-mcp and copper-bipy catalysts (see Figure attached) are considered. The main goal of the project is to provide a detailed description of the underlying reaction mechanisms at the molecular level. The data generated, including structures, energies, micro-thermodynamics and kinetics parameters, spectroscopy properties, etc..., will provide the clue to the further optimization of the catalytic activity and robustness of these systems. Molecular assemblies containing ruthenium catalysts functionalized with Ru-bipy and Ru-terpy photosensitizers will be also investigated. In this case, DFT and TDDFT computational models will be combined in order to infer the interplay between the catalytic and photochemical properties of these systems.

During the first reporting period of the project, the research activities have focused on the iridium-pyalk and copper-bipy catalysts. In the former case, DFT calculations including solvation have been used with the aim of determining the redox properties of these species, including the reduction potentials and their dependence on the pH. A wide range of metal oxidation states was derived by means of electron transfer (ET) and proton-coupled ET steps. The reactivity of the highest oxidation states towards O-O bond formation was also investigated by optimizing the transition states for the O-nucleophilic attack of water to the metal-oxo center. Spectroscopic properties, including IR and UV-Vis spectra, were also determined. A new dinuclear iridium-pyalk complex based on the bridging Ir-O-Ir moiety has been also investigated and one draft is currently in preparation.

In the copper-bipy system, the solvation dynamics of the catalyst were explored by means of classic, ab initio and hybrid molecular dynamics simulations. These studies revealed that the nature of anionic ligand cis to the reactive copper-oxo moiety, which can be an aqua (neutral), hydroxo (anionic) or oxo (dianionic) ligand, has a prominent impact on the first solvation sphere of the metal center. This can play a key role in the reaction because the solvent, water, is also the reactant. The radial distribution functions show that, due to hydrogen bonding interactions, the aqua ligand has the ability of concentrating a larger number of oxygen atoms in the vicinity of the reactive oxo ligand.

Due to several technical pitfalls in the study of these systems, including high energy pathways (iridium-pyalk), methodological problems (copper-bipy) and the work done by other competing groups (iron-mcp), other catalytic systems used in carbon dioxide recycling and Suzuki-Miyaura cross-coupling (SMCC) reactions have been also investigated. These new research lines, which diversify and add to the scope of the project within the same field (homogeneous computational catalysis), were opened by following the risk assessment plan included in the original project proposal. In addition, they are contributing to the extension of the research network associated with the project with a new collaboration with the Yale University in the USA (Prof. Hazari group). The computational work on carbon dioxide recycling focuses on the metal-catalyzed reduction to methanol through amides. The studies on the SMCC reaction revealed the possibility of increasing catalytic activity by preventing off-cycle deactivation routes. In a series of joint theoretical-experimental studies already published on high impact journals (ACS Catal., 2015, 5, 5596; ACS Catal., 2015, 5, 3680; Organometallics, 2015, 34, 381; J. Am. Chem. Soc., 2014, 136, 7300), this strategy yielded one of the most active catalysts reported to date. The topic of catalyst robustness was also studied in relation to catalytic dehydrogenation reactions in collaboration with the experimental group of Prof. Crabtree (Yale University, USA). This work has been also published already in Dalton Trans., 2015, 44, 18403 and Angew. Chem., Int. Ed., 2014, 53, 12808.

The computational studies planned for the second reporting period will focus on the catalytic oxidation of water by the photosensitizer systems. In addition, the catalytic recycling of carbon dioxide and SMCC reaction will be pursued further. The insight given by these studies will facilitate the optimization of these catalysts. The socio-economic impact of this research can be highly positive due to the high relevance of topics related to these catalysts, including renewable energies (water oxidation), climate change (carbon dioxide recycling) and medicine synthesis (SMCC reaction).
Besides these core research activities, other relevant actions were 1) training as trainer (teaching computational chemistry to MSc and PhD students) and trainee (research stay abroad for learning molecular dynamics), 2) participation in national and international conferences (five invited talks), 3) applications to external funding sources (two short-term fellowships granted), 4) publications in peer-reviewed international journals (see references above), 5) dissemination of the results over the Internet with a new webpage associated with the project ( These complementary activities will continue and extend during the second reporting period.

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