Independent Tuning of the p K a or the E 1/2 in a Family of Ruthenium Pyridine-Imidazole Complexes

• Published in: Inorganic chemistry 2023-07, Vol.62 (26), p.10031-10038
• Main Authors: Groff, Benjamin D, Cattaneo, Mauricio, Coste, Scott C, Pressley, Chloe A, Mercado, Brandon Q, Mayer, James M
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.3c01241

Two series of Ru (acac) (py-imH) complexes have been prepared, one with changes to the acac ligands and the other with substitutions to the imidazole. The proton-coupled electron transfer (PCET) thermochemistry of the complexes has been studied in acetonitrile, revealing that the acac substitutions almost exclusively affect the redox potentials of the complex (|Δ | ≫ |Δp |·0.059 V) while the changes to the imidazole primarily affect its acidity (|Δp |·0.059 V ≫ |Δ |). This decoupling is supported by DFT calculations, which show that the acac substitutions primarily affect the Ru-centered t orbitals, while changes to the py-imH ligand primarily affect the ligand-centered π orbitals. More broadly, the decoupling stems from the physical separation of the electron and proton within the complex and highlights a clear design strategy to separately tune the redox and acid/base properties of H atom donor/acceptor molecules.