Isomerization-Controlled Proton–Electron Coupling in a π-Planar Metal Complex

Abstract

Proton-coupled electron transfer (PCET) is a ubiquitous and fundamental process in biochemistry and electrochemistry performed by transition-metal complexes. Most synthetic efforts have been devoted to selecting the components, that is, metal ions and ligands, to control the proton–electron coupling. Here, we show the first example of controlling the proton–electron coupling using the cis–trans metal–ligand isomerization in a π-planar platinum complex, Pt(itsq)₂ (itsq¹⁻: o-iminothiosemiquinonate). Both the isomers, which were obtained separately, were characterized by single-crystal X-ray diffraction, and the cis-to-trans isomerization was achieved by immersing in organic solvents. Theoretical calculations predicted that the proton–electron coupling evaluated from the energetic stabilization of the lowest unoccupied molecular orbital by protonation varies greatly depending on the geometrical configuration compared to the metal substitution.