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A new family of monoanionic hemilabile ligands L1H-L3H with a PNN donor set has been developed, based on Pd-catalyzed C-N bond formation and straightforward phosphorylation. For these structurally related compounds with a hybrid set of donor atoms, the coordination chemistry with both Rh and Ir has been studied. The anticipated hemilabile character of the dimethylamino group was assessed by NMR and IR competition experiments, using isopropyl isocyanide as exogenous substrate. Supporting DFT calculations were used to quantify the electronic differences between the various members of the ligand family. In effect, we have constructed a modular ligand class that exhibits tunable hemilability.

The electronic coupling between a robust red algal photosystem I (PSI) associated with its light harvesting antenna (LHCI) and nanocrystalline n‐type semiconductors, TiO2 and hematite (α‐Fe2O3) is utilized for fabrication of the biohybrid dye‐sensitized solar cells (DSSC). PSI‐LHCI is immobilized as a structured multilayer over both semiconductors organized as highly ordered nanocrystalline arrays, as evidenced by FE‐SEM and XRD spectroscopy. Of all the biohybrid DSSCs examined, α‐Fe2O3/PSI‐LHCI biophotoanode operates at a highest quantum efficiency and generates the largest open circuit photo­current compared to the tandem system based on TiO2/PSI‐LHCI material. This is accomplished by immobilization of the PSI‐LHCI complex with its reducing side towards the hematite surface and nanostructuring of the PSI‐LHCI multilayer in which the subsequent layers of this complex are organized in the head‐to‐tail orientation. The biohybrid PSI‐LHCI‐DSSC is capable of sustained photoelectrochemical H2 production upon illumination with visible light above 590 nm. Although the solar conversion efficiency of the PSI‐LHCI/hematite DSSC is currently below a practical use, the system provides a blueprint for a genuinely green solar cell that can be used for molecular hydrogen production at a rate of 744 μmoles H2 mg Chl−1 h−1, placing it amongst the best performing biohybrid solar‐to‐fuel nanodevices.

To construct an efficient dye‐sensitized photo‐electrochemical tandem cell for hydrogen production, it is crucial to understand the working principles of both the photoanode and the photocathode. Herein, the anchoring of a proton‐reduction catalyst and an organic dye molecule on metal oxides is studied for the preparation of a photocathode. On TiO2, the Ni catalyst behaves as a good electrocatalyst (−250 μA cm−2) in acidic water (pH 2). The Ni catalyst and the organic dye were co‐immobilized on NiO to form a solely Ni‐based photocathode. The electron‐transfer steps were investigated by using various techniques (IR, UV/Vis, and fluorescence spectroscopy, and (photo)electrochemistry). Despite the observed successful single‐electron‐transfer steps between all of the components, photocatalysis did not yield any hydrogen gas. Possible bottlenecks that prevent photocatalytic proton reduction are poor electron transfer because of aggregation, charge recombination from the catalyst to the NiO, or instability of the catalyst after the first reduction.