Synthesis of N^P and P^N^N^P ligands and their Cu(I) complexes for the application in organic light-emitting diodes (OLEDs) and as photosensitizers in the photocatalytic hydrogen generation
Final Report Abstract
The project described in the original research proposal focused on the synthesis of novel multidentate ligands for the coordination of first row transition metals. The ligands as well as their Cu(I) complexes could be synthesized and characterized. However, studies of their photophysical properties showed that this type of compounds did not exhibit the expected and desired properties. The quantum yields were dramatically diminished compared to the published parent [Cu(N^N)(P^P)]+ complex although computer modelling predicted similar properties. As the structural and electrochemical parameters were similar, this significant change was probably due to non-radiative pathways resulting from the special properties of the tetradentate ligands. However, the ligands themselves may be useful for the coordination of different transition metals, e.g. for organometallic transition metal catalysts. Another research focus was the optimization of existing Ir(III) photosensitizers for the light-driven water reduction. Modification of the ligand backbone by adding vinyl moieties significantly enhanced the stability of the photocatalytic reduction system by increasing the interaction of photosensitizer and Pt water reduction catalyst. With this strategy, the water reduction systems remained active for 16–48 h instead of only 2–4 h catalytic activity of their parent non-vinyl complexes, resulting in quintupled amounts of evolved hydrogen. The best systems with more than 8000 turn-overs are amongst the top water-reduction systems reported so far. This new approach to increase the interaction of photosensitizer and Pt catalyst should prove very useful in optimizing existing and developing novel visible-light driven water-reduction systems of high stability.
Publications
- “Robust photocatalytic water reduction with cyclometalated Ir(III) 4-vinyl-2,2’-bipyridine complexes”, Chem. Commun. 2010, 46, 7551–7553
Stefan Metz and Stefan Bernhard
