{Reference Type}: Journal Article
{Title}: Tunning Energetics of 2e⁻/2H+ PCET Properties with Model Ru-bisamido Complexes.
{Author}: Cattaneo M;Gallmeier E;Abate PO;Mercado B;Mayer J;
{Journal}: Chemistry
{Volume}: 0
{Issue}: 0
{Year}: 2024 Jul 12
{Factor}: 5.02
{DOI}: 10.1002/chem.202401308
{Abstract}: Most redox processes that break/form bonds involve net 2e- changes, and many are coupled to protons. Yet most proton-coupled electron transfer (PCET) studies focus on 1e-/1H+ reactions. Reported here is a family of molecular models that undergo tunable 2e-/2H+ redox changes. Complexes [(X2bpy)RuII(en*)2](PF6)2 and [(X2bpy)RuIV(en*-H)2](PF6)2 have been synthesized with bpy = 2,2'-bipyridine with 4,4'-subtitutions X = -NMe2, -OMe, -Me, -H, -CF3; and en* = 2,3-dimethyl-2,3-butanediamine. They have been characterized by IR, UV-vis, and NMR spectroscopies, XRD, electrochemistry, mass spectrometry, DFT and (TD)DFT computations. The introduction of electron-withdrawing and donating groups at the 4,4'-position of the bpy ligand affects the complexes' redox potentials, pKa's, and Bond Dissociation Free Energies (BDFEs) of the N-H bonds in the en* ligands. The average BDFEs for the overall 2e-/2H+ PCET span over 5 kcal/mol. Notably, these complexes all show marked potential inversion over an extended range, ΔpKa > 25 units and ΔE0 > 1.4 V. Potential inversion remains despite the electronic influence of bpy's substitutions which regulate N-H properties several bonds apart by trans-effect over dπ-molecular orbitals at Ru-center. The experimental and computational results presented in this work support the presence of strong coupling between electrons and protons, for modelling insights of 2e-/2H+ transfer reactivity.