Photosensitizing Properties of Alkynylrhenium(I) Complexes [Re(–C≡C–R)(CO)₃(N∩N)] (N∩N = 2,2′‐bipy, phen) for H₂ Production

Abstract

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.

Hydrogen Evolution Catalyzed by Cobalt Diimine–Dioxime Complexes

“…Cobalt diimine-dioxime catalysts so far display lower activity under light driven conditions as compared to parent cobaloximes. 8a, 8c They however prove quite versatile as H 2 evolution catalysts as far as the reaction conditions are concerned: they function in pure organic solutions 47 as well as in fully aqueous conditions. 46, 48 Not surprisingly, the optimal acid/base conditions in terms of activity in water (up to 90 TON) correspond to a pH of 4, 48a thus matching the optimal value determined for the molecular-based cathode material containing the same cobalt diimine-dioxime catalytic moiety.…”

Φωτοκαταλυτική Παραγωγή Υδρογόνου Με Διθειολενικά Σύμπλοκα

“…Οι μοναδικές ιδιότητες των συμπλόκων του Re(I) τρικαρβονυλ-διιμίνη (tricarbonyl-diimine) είναι στενά συνδεδεμένες με την ύπαρξη μεταφοράς χαμηλής ενέργειας φορτίου της διεγερμένης κατάστασης με την μεταφορά μεγάλης ηλεκτρονιακής πυκνότητας από το μέταλλο στον υποκαταστάτη-διιμίνη (MLCTκατάσταση). Η γνώση της φωτοχημείας των συμπλόκων όπως το [Re(CO)3(bpy)X] βασίζεται σε μεθόδους που σχετίζονται με το χρόνο [108], υπολογισμούς DFT [29,109] και σχέσεις δομής -ιδιοτήτων [110]. Η φωτοκαταλυτική μετατροπή του διοξειδίου του άνθρακα σε μονοξείδιο του άνθρακα καταλυόμενη από το [ReBr(CO)3(bpy)] και οι εκτενείς έρευνες του μηχανισμού που ακολούθησαν [106,111] προάγουν την έρευνα αυτής της τάξης των συμπλόκων ως φωτοευαισθητοποιητών για την μετατροπή της ηλιακής ενέργειας.…”