A series of complexes of the type [fac‐Re(X)(CO)3(N∩N)] (X = –C≡C–R, N∩N = 2,2′‐bipy, 2,2′‐phen) were synthesized and fully characterized. Their photophysical characteristics make them very convenient photosensitizers (PSs). Upon light irradiation, H2 formation was observed for all alkynyl complexes in the presence of a water‐reducing catalyst (WRC) and a sacrificial electron donor. Relative rates of H2 production indicate a dependency upon the diimine ligands rather than upon the nature of the σ‐bonded alkynyl derivatives. The coordinated acetylene group induces a redshift of the λmax of the MLCT band in UV/Vis spectroscopy as compared to those of the corresponding halides, nitriles, or cationic ReI complexes, such as [fac‐ReX(CO)3(N∩N)] (X = pyridine, H2O, N∩N = bipy, phen).
Invited for the cover of this issue is the group of Roger Alberto at the University of Zürich, Switzerland. The cover image shows the reduction of protons by illumination of a catalytic mixture containing a cobalt-based waterreduction catalyst (WRC), a rhenium(I)-alkynyl photosensitizer, a proton source (H + ), and a sacrificial electron donor (D/D + ). The final product, hydrogen gas, stores the energy of light in its chemical bond.What is, in your opinion, an upcoming research theme likely to become one of the "hot topics" in the near future? Environment and health are two words which were, are, and always will be present in the minds of everyone. These two simple words have the power of connecting research groups all over the world, who try to solve problems addressed by these two words. That is why environmental and pharmaceutical interests are spread in a large number of institutions worldwide. While pharmaceutical advances already play an important role in our society, and huge progress has been achieved in this field of research, main issues in the area of environmental research remain open and still need to be solved. For instance: How to overcome the supply bottleneck of liquid fuels caused by depletion of the natural resources of fossil fuels? In our opinion, this "hot topic" will keep us busy until we can present an alternative and renewable energy source that fully replaces fossil fuels.
What are the main challenges in the broad area of your research?One of the main challenges of our research is to combine water oxidation and water reduction in one (homogeneous or heterogeneous) system to finally split water into hydrogen and oxygen, ideally with the use of sunlight. Electron back transfer reactionsthe so called electron shortcuts -between the molecules and components present in the reaction mixture are limiting the efficiency of water splitting in homogeneous systems. The understanding of these shortcut mechanisms is crucial for our research and helps us to address problems, which can then be systematically solved.
What aspects of this project do you find most exciting?The idea of catalysis and the design of a catalyst that is rapidly regenerated during the formation of a distinct product are more than fascinating. The challenge of understanding the catalytic cycle, the elucidation of its kinetics and clarifying the working mechanism behind it is a big incentive for these studies. It is always a great satisfaction to see a catalyst, developed by one's own hand and mind, working and undergoing numerous turnovers
2984in one cycle without losing its capacity to function in the way desired.
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