Timeresolved Spectroscopy of Artificial Photosynthetic Systems

Lead by Prof. Peter Hamm

Any chemical reaction cycle may, in principle, be elucidated by time-resolved spectroscopy, provided that its intermediates are transiently populated in sufficient amounts, and provided they exhibit characteristic marker bands. Just like natural photosynthetic systems, the artificial photosynthetic systems that will be developed in this project are perfectly suited to be investigated with essentially unlimited time-resolution by optical spectroscopy, as they are naturally photo-triggerable. UV-VIS and IR spectroscopy are intrinsically a very fast spectroscopies (in contrast to e. g. NMR spectroscopy), and report on electronic and chemical structure, respectively, as well as on the redox states of the molecular compounds involved in the systems to be developed. Using transient UV-VIS and IR spectroscopy covering all timescales from femtoseconds to hours, we investigate the electron transfer pathways between the various molecular components in homogeneous artificial photosynthetic systems developed in the groups of Roger Alberto and Greta Patzke. As a new line of research, we will also start to develop surface sensitive IR spectroscopic technique (SHG-2D-IR, SHG-pump-probe, ATR-pump-probe), as a future artificial photosynthetic system most likely will work with catalytic surfaces rather than in homogeneous solutions.

Figure 1: Typical IR response of a photosensitizer upon electron transfer to a hydrogen-evolution catalyst (see Inorg. Chem., 2009, 48 (5), 1836-1843 for details).



Figure 2: Laser Setup.