Design, synthesis and characterization of a modular bridging ligand platform for bio-inspired hydrogen production.

Synthesis and characterization of a novel type of ambident bridging ligands joining together the functional prerequisites for visible-light absorption, photoinduced electron transfer and catalytic proton reduction is presented. This class of compounds consists of a chromophoric 1,2-diimine-based π-acceptor site and a rigid polyaromatic dithiolate chelator. Due to the presence of a common conjugated linker moiety with an intrinsic two-electron redox reactivity and a suitable orbital coupling of the subunits, a favourable situation for vectorial multielectron transfer from attached electron donors to a catalytic acceptor site is provided. As an example for the application of this kind of bifunctional ligand systems, a [FeFe]-hydrogenase enzyme model compound is prepared and structurally characterized. Electrocatalytic hydrogen formation with this complex is demonstrated.