A new RuIIRhIII bimetallic with a single Rh-Cl bond as a supramolecular photocatalyst for proton reduction

A new (RuRhIII)-Rh-II structural motif [(bpy)(2)Ru(dpp)RhCl(tpy)](4+) with one halide on the Rh-III center demonstrates light-driven proton reduction ability, establishing that two halide ligands are not mandatory despite all prior systems containing a cis-RhCl2 catalytic site. This new design provides a novel approach to modulate Rh-III redox behavior and catalytic activity with insight into catalytic intermediates.