A 4H+/4e-Electron-Coupled-Proton Buffer Based on a Mononuclear Cu Complex

In this research article, we describe a 4H(+)/4e(-) electron-coupled-proton buffer (ECPB) based on Cu and a redox-active ligand. The protonated/reduced ECPB (complex 1: [Cu(8H(+)/14e(-))]1+), consisting of CuI with 2 equiv of the ligand ((LH4)-L-cat: 1,1 '-(4,5-dimethoxy-1, 2-p henylene)b is (3-(tert-butyl)-urea)), reacted with H+/e(-) acceptors such as O-2 to generate the deprotonated/oxidized ECPB. The resulting compound, (complex 5: [Cu(4H(+)/10e(-))](1+)), was characterized by X-ray diffraction analysis, nuclear magnetic resonance (H-1-NMR), and density functional theory, and it is electronically described as a cuprous bis(benzoquinonediimine) species. The stoichiometric 4H(+)/4e(- )reduction of 5 was carried out with H+/e(-) donors to generate 1 (CuI and 2 equiv of (LH4)-L-cat) and the corresponding oxidation products. The 1/5 ECPB system catalyzed the 4H(+)/4e(-) reduction of O-2 to H2O and the dehydrogenation of organic substrates in a decoupled (oxidations and reductions are separated in time and space) and a coupled fashion (oxidations and reductions coincide in time and space). Mechanistic analysis revealed that upon reductive protonation of 5 and oxidative deprotonation of 1, fast disproportionation reactions regenerate complexes 5 and 1 in a stoichiometric fashion to maintain the ECPB equilibrium.

Automated summary

In this research article, a 4H(+)/4e(-) electron-coupled-proton buffer (ECPB) based on Cu and a redox-active ligand is described. The ECPB system catalyzes both the reduction of O-2 to H2O and the dehydrogenation of organic substrates. Mechanistic analysis reveals that fast disproportionation reactions maintain the ECPB equilibrium.