Development of better molecular catalysts for water splitting and solar fuels formation is a major topic in current artificial photosynthesis research. Rational design and comparative studies rely, however, on detailed information about the mechanism of catalysis that in most cases is not available. In contrast, turnover frequencies are often reported for overall product formation under conditions where the actual catalytic steps are not rate limiting and no information on the critical reaction steps is obtained. Experimental studies under conditions where the mechanism can be determined and/or intermediate steps be followed are clearly desirable in order to allow for rational design and evaluation of new catalysts.We have for some years developed mono- and dinuclear iron complexes for catalytic proton reduction inspired by the active site of [FeFe]-hydrogenase. We have demonstrated e.g. the catalytic effect of a protonable base near the active site, the construction of sensitizer-catalyst dyads, complex patterns of ligand vs. metal protonation, multi-turnover photochemical hydrogen production and the first penta-coordinate mononuclear catalyst mimicking the distal iron center.In this paper we will present studies were we directly resolve unstable intermediates of the catalytic reaction in solution by time-resolved spectroscopy. We will also present the first spectroscopic evidence for dye-sensitized formation of reduced iron-catalyst species anchored onto a dye-sensitized NiO film.

Mechanistic investigations and detection of intermediates of molecular proton reduction catalysts

247th National Meeting (2014)

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