Matthias Beller, Leibniz-Institut für Katalyse an der Universität Rostock e.V., Germany, and international colleagues describe the synthesis and characterization of a series of cationic Cu^I complexes of the type [Cu(N^N)(P^P)]⁺ and their function as active photosensitizers in the photocatalytic hydrogen generation from water at room temperature under basic conditions. This is the first efficient noble-metal-free photocatalytic system for proton reduction using copper-based photosensitizers.

The novel system makes use of Cu^I complexes as photosensitizers (PS) and [Fe₃(CO)₁₂] as a water reduction catalyst (WRC) in the presence of triethylamine (TEA) as a sacrificial reductant (SR); pictured above. As the Cu^I complexes are relatively inexpensive, readily available from commercial sources, and stable to ambient conditions, they are an attractive alternative to the widely used iridium and other noble-metal-based PS systems.

The team expects further improvements by tuning the properties of the copper center with related ligands as well as by potential heterogenization of the systems. Because of their photochemical behavior, these systems are also of interest for applications like OLEDs and LEC.

• Photocatalytic Water Reduction with Copper-Based Photosensitizers: A Noble-Metal-Free System,
  Shu-Ping Luo, Esteban Mej_a, Aleksej Friedrich, Alexandra Pazidis, Henrik Junge, Annette-Enrica Surkus, Ralf Jackstell, Stefania Denurra, Serafino Gladiali, Stefan Lochbrunner, Matthias Beller,
  Angew. Chem. Int. Ed. 2013, 52, 419–423.
  DOI: 10.1002/anie.201205915